Metal-free, Regio-, and Stereo-Controlled Hydrochlorination and Hydrobromination of Ynones and Ynamides.

We developed an atom-economical and metal-free method for the regio- and stereo-selective hydrohalogenation of ynones and ynamides using easy to handle DMPU/HX (X = Br or Cl) reagents. The reaction operates under mild conditions and a range of functional groups is well tolerated. We propose that the hydrohalogenation of ynones gives the anti-addition products via a concerted multimolecular AdE3 mechanism and that the hydrohalogenation of ynamides produces the syn-addition products via a cationic keteniminium intermediate.

Introduction

Vinylhalides are important targets in medicine and materials, and they are also important substrates for cross-coupling reactions.[1] More specifically, halogenated vinyl ketones and halogenated N-vinyl amides (enamides) are especially important targets and synthetic building blocks because they are highly functional sources of vinyl halides.[2] The hydrohalogenation of alkynes has provided a uniform approach toward viny halides,[1g,3] and the most straightforward and atom-economical synthesis of halogenated vinyl ketones and haloethenamides has been the regio- and stereo-selective hydrohalogenation of ynones and ynamides, respectively (Scheme , top). For example, the hydrohalogenation of ynones using HBr/water,[4] AlBr3/H2O or LiBr/TFA,[4c] HCl/water,[5] and SnCl4/H2O[5,6] (Scheme a–e) have been reported, but these methods give poor chemical yields due to side reactions, such as hydration. For the hydrohalogenation of ynamides, Hsung and co-workers reported a stereoselective synthesis of 1-haloenamides using in situ generated HX from MgX2 in a wet solvent (Scheme f).[7] Iwasawa and co-workers reported the hydrochlorination of terminal ynamides using HX generated in situ from TMSX and water (Scheme g).[8] Sahoo and co-workers demonstrated a one-pot construction of haloenamides using a Ph3P/H2O/CX4 system as the halide source (Scheme h).[9] Recently, Shin and co-workers reported a novel benzoic acid-catalyzed hydrohalogenation of ynamides using N-oxides/dihalogenated ethane system (Scheme d)[10] whereas Thibaudeau and co-workers reported a syn-addition of HF to the ynamides.[11] Although the above-mentioned examples underscore the importance of halogenation protocols, the reported methods are either too narrow in scope, or suffer from complex reaction conditions, low chemical yields, and/or poor atom-economy. What is needed is a simple, unified, chemo- and stereo-selective atom-economical hydrohalogenation method for a wide range of ynones and ynamides.

Scheme 1

Halogenation of Ynones and Ynamides

Recently, we reported a metal-free, hydrogen bonding cluster-enabled addition of sulfonic acids to haloalkynes.[12] We now postulate that a metal-free and atom-economic hydrochlorination or hydrobromination of ynones 1 and ynamides 4 is possible using HX. However, hydrogen halides, such as hydrogen chloride and hydrogen bromide, are hazardous gases at room temperature. Although many HX reagents (e.g., Et2O/HCl, H2O/HCl, isopropanol/HCl, HOAc/HBr, H2O/HBr) are commercially available, they exist either in low concentration (e.g., Et2O/HCl) and/or in protic media (H2O, isopropanol, HOAc) where the protic solvent hampers the nucleophilicity of HX and also competes with HX in nucleophilic addition. This effect may explain the low efficiency when protic solutions of HX are used (Scheme ). In this regard, an HX solution in a neutral aprotic medium would be optimal to prevent competitive solvolysis reaction and to achieve high reactivity. Due to its high hydrogen bond basicity, yet low Brønsted basicity,[13,14] DMPU (1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone) can form a stable and highly concentrated complex with hydrogen chloride (HCl) and hydrogen bromide (HBr); we have used these complexes in nanogold catalyzed or noncatalyzed hydrohalogenation of alkenes and alkynes.[15] We are now glad to report an atom-economical and metal-free method for the regio- and stereo-selective hydrohalogenation of ynones and ynamides using easy to handle DMPU/HX (X = Br or Cl) reagents.

Results and Discussion

We carried out the hydrochlorination of 1a as our model reaction (Table ). We were delighted to find that DMPU/HCl gave better yields, higher anti-selectivity and fewer byproducts compared to commercial HCl reagents (Table , entries 1–4). Mixing DMPU/HCl with 1a in DCM from 0 °C to room temperature produced the desired product, chloro-unsaturated ketone 2, in 98% yield (Table , entry 4). Screening of other solvents indicated that weakly coordinating solvents like DCM, DCE, and toluene were better than more coordinating solvents such as CH3CN, THF, and DMF (Table , entries 5–9).

Table 1

Optimization of the Hydrochlorination of Alkynyl Ketonea

entry	HCl reagent	solvent	2/%b (2a:2a’) (anti:syn)
1	Et2O/HCl	DCM	70 (6:1)
2	1,4-dioxane/HCl	DCM	81 (7:1)
3	isopropanol/HCl	DCM	92 (3:1)
4	DMPU/HCl	DCM	98 (12:1)
5	DMPU/HCl	MeCN	89 (6:1)
6	DMPU/HCl	toluene	88 (7:1)
7	DMPU/HCl	THF	83 (5:1)
8	DMPU/HCl	DMF	78 (2:1)
9	DMPU/HCl	DCE	97 (8:1)

Reaction conditions: 1a (0.2 mmol), HCl reagent (0.4 equiv) in solvent (0.5 mL), 0 °C to rt for 8 h.

Determined by GC-MS analysis.

With the optimized conditions in hand, we explored the substrate scope and functional group tolerance for the hydrochlorination of alkynyl ketones (Table , top). We evaluated the effect of different [R1, R2] combinations of ynones 1 (Table ). Combinations of [R1 = aryl, R2 = alkyl] (Table , 2a–l), [R1 = aryl, R2 = aryl] (Table , 2n), [R1 = alkyl, R2 = aryl] (Table , 2o) worked very well; good chemical yields and high anti-selectivity were observed. The bulky R2 groups (e.g., t-Bu, Cy-) did not affect chemical yields (Table , 2b, 2c). Equally, the substitution pattern (meta, para) or the electronic properties of the substituents (electron deficient or rich) on R1 or R2 played only a small role; good yields were obtained regardless (Table , 2e–2m, 2o). Various functional groups, such as esters (Table , 2e, 2k), ether (Table , 2i), halides (Table , 2f, 2h), nitrile (Table , 2l), nitro (Table , 2o), and sulfonate (Table , 2j), were well tolerated. Similar conditions worked very well for the hydrobromination of ynones when DMPU/HBr was used (Table , bottom). In these cases, we observed a very similar reactivity pattern and functional group tolerance (Table , 3a–3j). We also tested the hydrohalogenation of dialkyl substituted ynones. Unfortunately we got mostly hydration products and other byproducts. We also attempted to conduct hydroiodination using DMPU-HI reagent, but the preparation of DMPU-HI was not successful (formation of I2 when mixing HI and DMPU).

Table 2

Hydrohalogenation of Ynonesa

Reaction conditions: ynones 1 (0.2 mmol), DMPU/HX (0.4 mmol) in DCM (0.5 mL), 0 °C to rt for 8 h; trace syn-addition products were also observed in most case, but they can be easily removed by chromatography.

Ynamides are readily available compounds that have found wide applications in organic synthesis.[16] We were glad to find that our protocol can also be used in the hydrohalogenation of ynamides 4 (Table ). We first explored the substrate scope and functional group tolerance in the hydrobromination of ynamides 4 (Table , top). Despite the strong acidity of the DMPU/HBr complex and the fact that ynamides are acid sensitive compounds, the substrate scope was broad: both aliphatic and aromatic substituted ynamides produced syn-addition products exclusively in good to excellent yields (Table ): combinations of [EWG = Ts, R2 = Bn], [EWG = Ts, R2 = n-heptyl], [EWG = Ms, R2 = methyl], [EWG = Ms, R2 = phenyl] all gave good yields (Table , 5a–d). Also, the substitution pattern (para-, ortho-, or meta-) on the aryl ring of R1 only had a small effect on the efficiency of the reaction, high yields were obtained regardless (Table , 5e–5i). It should be noted that acid sensitive functional groups such as nitrile and methyl ester survived our conditions (Table , 5j–5k).

Table 3

Hydrohalogenation of Ynamidesa

Reaction conditions: ynamide 1 (0.2 mmol), DMPU/HX (0.4 mmol) in DCM (0.5 mL), 0 °C to rt for 8 h.

Next, we investigated the hydrochlorination of ynamides 4 using DMPU/HCl as the chlorination reagent (Table , bottom). This protocol also had wide substrate scope and good functional group tolerance (Table bottom). Ynamides 4 with combinations of [EWG = Ts/Ms/carbamate, R2 = alkyl, aryl, allyl, homoallyl] delivered 6 in good yields as well as in excellent regio- and stereo-control (Table , 6a–g). Interestingly, acid sensitive functional groups, such as alkene, allyl, and carbamate, survived the reaction conditions. We also investigated the effects of the substitution pattern in R1 on the efficiency of reactions. For ynamides with various R1 groups (R1 = naphthyl, phenyl rings with electron-donating groups or electron-withdrawing groups, heteroaryls such as thiophene), high yields of 6 were obtained regardless (Table , 6h–o). Remarkably, ynamides featuring a complex cholesterol scaffold furnished the desired chlorinated product in 82% yield (Table , 6o).

Our methodology can be used in larger scale synthesis without complications. The hydrohalogenation of ynone 1a (5 mmol scale) gave chlorinated product 2a and brominated product 3a in 85% and 73% yields, respectively (Scheme a). Ynamide 4a (1.0 g scale) was successfully converted to 6a in 93% yield (Scheme b).

Scheme 2

Gram Scale Hydrohalogenations

Next, we utilized these halogenated alkene products in transition metal catalyzed cross-coupling reactions (Scheme ). Suzuki coupling of halogenated vinyl ketones 2 and 3 with phenyl boronic acid gave good yields of the coupling products (Scheme a). Similarly, the Pd catalyzed Suzuki coupling of chlorinated enamide 6a with phenyl boronic acid (Scheme b), and the Sonogashira coupling of brominated enamide 5c with ethynyltrimethylsilane (Scheme c) gave good yields of trisubstituted enamides 8a and 9a, respectively. On the other hand, copper catalysts, such as CuCN, were not a good catalyst for coupling of 5c.

Scheme 3

Divergent Syntheses from Halogenated Products

Our proposed mechanism is shown in Scheme . For the hydrohalogenation of ynamides (Scheme a), the high acidity of DMPU/HX facilitates the rate-determining proton transfer step, which produces the key intermediate, keteniminium A.[17] Because the nitrogen atom polarizes the triple bond, the regioselectivity of this protonation is mainly determined by the charge distribution on C1 and C2 of ynamide 4. Due to the resonance contribution of the lone pair on the nitrogen atom, the NBO charge density of C2 is significantly higher than C1, so DMPU/HX should protonate C2 preferentially (Scheme a). This pathway eventually leads to the α-regioselectivity observed. Also, DFT geometry optimization of A indicates that the keteniminium intermediate possesses a linear geometry, with its upper face being sterically hindered by the R1 group, thus favoring the nucleophile (bromide/chloride) syn approach (formation of the syn-addition product).[11b]

Scheme 4

Proposed Mechanism

LUMO of keteniminium was calculated at B3LYP/6-311+G(2df,2p) level of theory.

For the hydrohalogenation of the electron deficient ynone 1, the direct protonation of 1 is more difficult, so we proposed a different mechanism (Scheme b). The exclusive formation of the Z-isomer (anti-addition) suggested the possibility of an AdE3 mechanism[18] because the bromide concentration in the reaction medium is not low.[19] This concerted three-molecule process should furnish the anti-addition product. The regio-selectivity found can be rationalized by the fact that the NBO charge density of C1 is significantly higher than C2 because of the resonance participation of the carbonyl group (Scheme b). This pathway should eventually lead to the β-regioselectivity found.

Conclusion

In conclusion, we have developed an atom-economical and metal-free method for the regio- and stereo-selective hydrohalogenation of ynones and ynamides using easily handled DMPU/HX (X = Br or Cl) reagents. The reaction operates under mild conditions and a range of functional groups are well tolerated. Further applications of these new halogenation reagents are currently underway in our laboratory and will be reported in due course.

Experimental Section

1H NMR (400 or 500 MHz) and 13C NMR (100 or 125 MHz) spectra were recorded on a Bruker NMR apparatus. The chemical shifts are reported in δ (ppm) values (1H and 13C NMR relative to CHCl3, δ 7.26 ppm for 1H NMR and δ 77.0 ppm for 13C NMR). Or alternatively, 1H NMR chemical shifts were referenced to tetramethylsilane signal (0 ppm). Multiplicities are recorded by s (singlet), d (doublet), t (triplet), q (quartet), p (pentet), h (hextet), m (multiplet), and br (broad). Coupling constants (J), are reported in Hertz (Hz). GC analyses were performed using a Shimadzu GC-2010 ultra gas chromatography–mass spectrometry instrument equipped with a Shimadzu AOC-20s autosampler. Commercial reagents and solvents were obtained from the commercial providers and used without further purification. The products were purified using a commercial flash chromatography system or a regular glass column. TLC was developed on silica gel 60 F254 glass plates. The DMPU/HX reagents were prepared using our published procedures.[15]

Methyl 3-(3-oxooct-1-yn-1-yl) Benzoate (1e)[20]

White solid. 1H NMR (400 MHz, chloroform-d) δ 8.23 (s, 1H), 8.10 (d, J = 6.6 Hz, 1H), 7.73 (d, J = 7.2 Hz, 1H), 7.47 (s, 1H), 3.93 (s, 3H), 2.66 (t, J = 7.2 Hz, 2H), 1.91–1.67 (m, 2H), 1.35 (d, J = 3.3 Hz, 4H), 0.91 (t, J = 7.5 Hz, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 187.9, 165.8, 136.9, 133.9, 131.3, 130.8, 128.7, 120.6, 88.8, 88.2, 52.5, 45.5, 31.1, 23.8, 22.3, 13.8. HRMS (ESI-FT-ICR) calcd. for C16H19O3 [M+H]+: 259.1334, found: 259.1327.

4-(4-Fluoro-3-methylphenyl)but-3-yn-2-one (1h)

Yellow solid. Mp 42–43 °C. 1H NMR (400 MHz, chloroform-d) δ 7.61–7.33 (m, 2H), 7.00 (t, J = 8.8 Hz, 1H), 2.42 (s, 3H), 2.26 (s, 3H). 19F NMR (376 MHz, chloroform-d) δ −109.52 – −112.87 (m). 13C{1H} NMR (100 MHz, chloroform-d) δ 184.4, 162.7 (d, J = 252.4 Hz), 136.5, 132.7 (d, J = 8.9 Hz), 125.9 (d, J = 18.2 Hz), 115.8, 115.6, 89.7, 87.9, 32.6 (d, J = 5.3 Hz), 14.3. HRMS (ESI-FT-ICR) calcd. for C12H10FO [M+H]+: 177.0710, found: 177.0703.

3-(3-Oxobut-1-yn-1-yl)phenyl methanesulfonate (1j)[20]

White solid. 1H NMR (400 MHz, chloroform-d) δ 7.57–7.34 (m, 4H), 3.17 (s, 3H), 2.44 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 184.1, 148.8, 131.8, 130.4, 126.2, 124.6, 122.0, 88.9, 87.6, 37.7, 32.7. HRMS(ESI-FT-ICR) calcd. for C11H11SO4[M+H]+: 239.0378, found:239.0371.

Methyl 3-(3-oxobut-1-yn-1-yl)benzoate (1k)[20]

White solid. 1H NMR (400 MHz, chloroform-d) δ 8.22 (s, 1H), 8.12–8.00 (m, 1H), 7.79–7.64 (m, 1H), 7.46–7.42 (m, 1H), 3.92 (s, 3H), 2.44 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 184.2, 165.8, 136.8, 134.0, 131.5, 130.8, 128.8, 120.4, 88.6, 88.5, 52.4, 32.7. HRMS (ESI-FT-ICR) calcd. for C12H11O3[M+H]+: 203.0708, found:203.0720.

4-(3-Oxobut-1-yn-1-yl)benzonitrile (1l)[20]

White solid. 1H NMR (400 MHz, chloroform-d) δ 7.66–7.63 (m, 4H), 2.46 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 183.9, 133.2, 132.2, 124.7, 117.8, 113.9, 90.5, 86.8, 32.7. HRMS (ESI-FT-ICR) calcd. for C11H8NO[M+H]+: 170.0606, found:170.0600.

4-(4-Acetylphenyl)but-3-yn-2-one (1m)[20]

White solid. 1H NMR (400 MHz, chloroform-d) δ 7.93 (d, J = 8.2 Hz, 2H), 7.62 (d, J = 8.2 Hz, 2H), 2.59 (s, 3H), 2.44 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 196.9, 184.2, 138.0, 133.0, 128.3, 124.5, 89.9, 88.3, 32.7, 32., 26.64. HRMS (ESI-FT-ICR) calcd. for C12H11O2[M+H]+:187.0759, found:187.0753.

Synthesis of Ynamides 4

General Procedure

To a mixture of alkynyl bromide (3.0 mmol), 1,10-phenanthroline (0.6 mmol, 108 mg), CuSO4·5H2O (0.3 mmol,149 mg), and K2CO3 (6.0 mmol, 828 mg) in dry toluene (15.0 mL), amide (3.6 mol) was added. The reaction mixture was stirred at 70 °C under the nitrogen atmosphere. The progress of the reaction was monitored periodically by TLC. After the completion of the reaction, the reaction mixture was filtered through a pad of Celite and the solvent was removed in vacuum. The resulting residue was purified by chromatography on silica gel to give the desired products.

N-(2-(Cyclohex-1-en-1-yl)ethyl)-4-methyl-N-(phenylethynyl)benzenesulfonamide (4f)

Pale yellow oil. 1H NMR (500 MHz, chloroform-d) δ 7.86 (d, J = 8.3 Hz, 2H), 7.46–7.34 (m, 4H), 7.35–7.26 (m, 3H), 5.48 (s, 1H), 3.65–3.34 (m, 2H), 2.47 (s, 3H), 2.33 (t, J = 7.6 Hz, 2H), 1.99–1.94 (m, 4H), 1.73–1.59 (m, 2H), 1.57–1.52 (m, 2H).13C{1H} NMR (100 MHz, chloroform-d) δ 144.5, 134.8, 133.3, 131.3, 129.7, 128.3, 127.7, 124.2, 123.0, 82.5, 70.8, 50.3, 36.4, 28.2, 25.3, 22.8, 22.2, 21.7. HRMS (ESI-FT-ICR) calcd. for C23H26NO2S [M+H]+: 380.1684, found: 380.1678.

(3S,10R,13R,17R)-10,13-Dimethyl-17-((R)-6-methylheptan-2-yl)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-3-yl 6-((N,4-dimethylphenyl)sulfonamido)hex-5-ynoate (4o)

White solid. Mp 94–95 °C. 1H NMR (400 MHz, chloroform-d) δ 7.76 (d, J = 8.3 Hz, 2H), 7.34 (d, J = 7.9 Hz, 2H), 5.35 (d, J = 4.9 Hz, 1H), 4.62–4.60 (m, 1H), 2.99 (s, 3H), 2.43 (s, 3H), 2.35–2.31 (m, 6H), 2.07–1.05 (m, 28H), 1.00 (s, 3H), 0.89 (d, J = 6.5 Hz, 3H), 0.85 (d, J = 1.8 Hz, 3H), 0.83 (d, J = 1.8 Hz, 3H), 0.66 (s, 3H).13C{1H} NMR (100 MHz,) δ 172.5, 144.5, 139.6, 133.1, 129.7, 127.8, 127.7, 122.6, 75.6, 74.0, 67.4, 56.7, 56.1, 50.0, 42.3, 39.7, 39.5, 38.1, 37.0, 36.6, 36.2, 35.8, 33.4, 31.9, 31.8, 28.2, 28.0, 27.8, 24.2, 23.8, 22.8, 22.5, 21.7, 21.0, 19.3, 18.7, 17.9, 11.8. HRMS (ESI +) calcd. for C41H61NO4S [M+H]+: 664.4400, found: 664.4385.

Hydrochlorination of Ynones 1

To a solution of ynone 1 (0.2 mmol) in DCM (0.5 mL) was added DMPU/HCl (43 wt/wt%) (34 mg, 0.4 mmol) at 0 °C, then the mixture was warmed to room temperature and was stirred for 8 h. After completion, the solvent was evaporated under the reduced pressure and the residue was purified by silica gel column chromatography (hexanes/EtOAc as elute solvent) to afford the corresponding products 2.

(Z)-4-Chloro-4-phenylbut-3-en-2-one (2a)[3e]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20)give the product as colorless oil, 30.2 mg 84% yield. 1H NMR (400 MHz, chloroform-d) δ 7.86–7.55 (m, 2H), 7.58–7.31 (m, 4H), 6.77 (s, 1H), 2.47 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 196.7, 143.1, 137.3, 130.7, 128.6, 127.3, 124.7, 31.9.

(Z)-1-Chloro-4,4-dimethyl-1-phenylpent-1-en-3-one (2b)[21]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20)give the product as yellow oil, 40.8 mg, 92% yield. 1H NMR (400 MHz, chloroform-d) δ 7.77–7.56 (m, 2H), 7.59–7.25 (m, 3H), 7.06 (s, 1H), 1.22 (s, 9H).13C{1H} NMR (100 MHz, chloroform-d) δ 203.6, 143.2, 137.8, 130.4, 128.6, 127.2, 119.9, 44.5, 26.3. HRMS (ESI-FT-ICR) calcd. for C13H16ClO[M+H]+: 223.0890, found: 223.0885.

(Z)-3-Chloro-1-cyclohexyl-3-phenylprop-2-en-1-one (2c)[22]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20)give the product as yellow oil, 42.1 mg, 85% yield. 1H NMR (400 MHz, chloroform-d) δ 7.90–7.51 (m, 2H), 7.41–7.36 (m, 3H), 6.84 (s, 1H), 2.58–2.54 (m, 1H), 1.92–1.90 (m, 2H), 1.80–1.78 (m, 2H), 1.67–1.65 (m, 1H), 1.50–1.05 (m, 5H). 13C{1H} NMR (100 MHz, chloroform-d) δ 201.5, 142.6, 137.55, 130.47, 128.57, 127.24, 122.66, 51.63, 28.35, 25.85, 25.65. HRMS (ESI-FT-ICR) calcd. for C15H18ClO [M+H]+: 249.1046, found: 249.1039.

(Z)-1-Chloro-1-phenyloct-1-en-3-one (2d)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow oil, 41.5 mg, 88% yield. 1H NMR (400 MHz, chloroform-d) δ 7.67–7.75 (m, 2H), 7.50–7.30 (m, 3H), 6.78 (s, 1H), 2.68 (t, J = 7.4 Hz, 2H), 1.67- 1.63 (m, 2H), 1.33–1.30 (m, 4H), 0.90 (t, J = 6.8 Hz, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 199.01, 142.31, 137.44, 130.53, 128.59, 127.26, 123.86, 44.44, 31.38, 23.68, 22.48, 13.92. HRMS (ESI-FT-ICR) calcd. for C14H18ClO [M+H]+: 237.1046, found: 237.1040.

Methyl (Z)-3-(1-Chloro-3-oxooct-1-en-1-yl)benzoate (2e)

Purified by flash column chromatography (ethyl acetate/hexanes = 1/20), yellow oil. NMR (400 MHz, chloroform-d) δ 8.31 (s, 1H), 8.07 (d, J = 7.1 Hz, 1H), 7.85 (d, J = 7.1 Hz, 1H), 7.48 (t, J = 7.8 Hz, 1H), 6.83 (s, 1H), 3.93 (s, 3H), 2.68 (t, J = 7.3 Hz, 2H), 1.87–1.59 (m, 2H), 1.35–1.29 (m, 4H), 0.88 (t, J = 6.6 Hz, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 198.8, 166.2, 140.9, 137.8, 131.5, 131.4, 130.7, 128.8, 128.2, 124.8, 52.4, 44.5, 31.4, 23.6, 22.5, 13.9. HRMS (ESI-FT-ICR) calcd. for C16H20ClO3 [M+H]+: 295.1101, found: 295.1094.

(Z)-4-Chloro-4-(4-chlorophenyl)but-3-en-2-one (2f)

Purified by flash column chromatography (ethyl acetate/hexane= 1:20)give the product as pale yellow oil, 35 mg, 82% yield. 1H NMR (400 MHz, chloroform-d) δ 7.60 (d, J = 8.6 Hz, 2H), 7.37 (d, J = 8.6 Hz, 2H), 6.73 (s, 1H), 2.46 (s, 3H).13C{1H} NMR (100 MHz, chloroform-d) δ 196.3, 141.6, 136.9, 135.7, 128.9, 128.5, 124.9, 31.9. HRMS (ESI-FT-ICR) calcd. for C10H9Cl2O [M+H]+: 215.0030, found: 215.0024.

(Z)-4-(4-Bromophenyl)-4-chlorobut- 3-en-2-one (2g)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow solid, 44.8 mg, 88% yield. Mp 42–43 °C 1H NMR (400 MHz, chloroform-d) δ 7.53 (s, 4H), 6.74 (s, 1H), 2.45 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 196.7, 141.7, 136.1, 131.9, 128.7, 125.2, 124.9, 31.9. HRMS (ESI-FT-ICR) calcd. for C10H7ClBrO [M-H+]: 256.9369, found: 256.9362.

(Z)-4-Chloro-4-(4-fluoro-3-methylphenyl)but-3-en-2-one (2h)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow oil, 38.1 mg, 90% yield. 1H NMR (400 MHz, chloroform-d) δ 7.48–7.42 (m, 2H), 7.01 (t, J = 8.8 Hz, 1H), 6.69 (s, 1H), 2.44 (s, 3H), 2.28 (s, 3H). 19F NMR (376 MHz, chloroform-d) δ −101.3 – −135.0 (m, 1F). 13C{1H} NMR (100 MHz, chloroform-d) δ 196.4, 162.7 (d, J = 250.8 Hz), 142.1, 133.1 (d, J = 3.8 Hz), 130.7 (d, J = 6.1 Hz), 126.7 (d, J = 8.7 Hz), 125. Four (d, J = 17.9 Hz), 124.3, 115.3 (d, J = 23.1 Hz), 31.9, 14.6 (d, J = 3.3 Hz). HRMS (ESI-FT-ICR) calcd. for C11H11ClFO [M+H]+: 213.0482, found:213.0477.

(Z)-4-Chloro-4-(3-methoxyphenyl)but-3-en-2-one (2i)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow oil, 31.9 mg,76% yield. 1H NMR (400 MHz, chloroform-d) 7.29 (t, J = 7.9 Hz, 1H), 7.23 (d, J = 7.8 Hz, 1H), 7.18 (s, 1H), 7.00–6.91 (m, 1H), 6.75 (s, 1H), 3.82 (s, 3H), 2.45 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 196.6, 159.6, 142.7, 138.7, 129.6, 124.9, 119.6, 116.3, 112.9, 55.4, 31.9. HRMS (ESI-FT-ICR) calcd. for C11H12ClO2 [M+H]+: 211.0526, found: 211.0519.

(Z)-3-(1-Chloro-3-oxobut-1-en-1-yl)phenyl methanesulfonate (2j)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:10), pale red oil, 46.5 mg, 85% yield. 1H NMR (400 MHz, chloroform-d) δ 7.63 (d, J = 7.9 Hz, 1H), 7.58 (s, 1H), 7.46 (t, J = 8.0 Hz, 1H), 7.36 (ddd, J = 8.1, 2.5, 1.1 Hz, 1H), 6.77 (s, 1H), 3.18 (s, 3H), 2.46 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 196.3, 149.1, 140.6, 139.4, 130.3, 126.1, 125.8, 124.1, 121.1, 37.7, 31.9. HRMS (ESI-FT-ICR) calcd. for C11H12ClSO4 [M+H]+: 275.0145, found:275.0140.

Methyl (Z)-3-(1-Chloro-3-oxobut-1-en-1-yl)benzoate (2k)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), yellow solid, 40.9 mg, 86% yield. Mp 44–45 °C 1H NMR (400 MHz, chloroform-d) δ 8.31 (s, 1H), 8.08 (d, J = 7.7 Hz, 1H), 7.85 (d, J = 8.9 Hz, 1H), 7.49 (t, J = 7.8 Hz, 1H), 6.82 (s, 1H), 3.93 (s, 3H), 2.47 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 196.4, 166.1, 141.6, 137.6, 131.5, 130.7, 128.9, 128.2, 125.4, 52.4, 31.9. HRMS (ESI-FT-ICR) calcd. for C12H12ClO3 [M+H]+: 239.0475, found:239.0470.

(Z)-4-(1-Chloro-3-oxobut-1-en-1-yl)benzonitrile (2l)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:10), yellow solid, 33.2 mg, 81% yield. Mp 76–78 °C. 1H NMR (400 MHz, chloroform-d) δ 7.77 (d, J = 8.3 Hz, 2H), 7.70 (d, J = 8.3 Hz, 2H), 6.79 (s, 1H), 2.47 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 196.1, 141.4, 140.2, 132.4, 127.9, 126.8, 117.9, 114.1, 31.8. HRMS (ESI-FT-ICR) calcd. for C11H9ClNO [M+H]+: 206.0373, found: 206.0366.

(Z)-4-(4-Acetylphenyl)-4-chlorobut-3-en-2-one (2m)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), yellow oil, 37.4 mg, 85% yield. 1H NMR (400 MHz, chloroform-d) 7.97 (d, J = 8.5 Hz, 2H), 7.75 (d, J = 8.6 Hz, 2H), 6.81 (s, 1H), 2.61 (s, 3H), 2.48 (s, 3H). 13C{1H} NMR (100 MHz, chloroform-d) δ 197.1, 196.4, 141.3, 138.4, 128.5, 127.5, 126.2, 31.9, 26.7. HRMS (ESI-FT-ICR) calcd. for C12H12ClO2 [M+H]+: 223.0526, found: 223.0520.

(Z)-3-Chloro-1,3-diphenylprop-2-en-1-one (2n)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow oil, 43 mg, 89% yield. 1H NMR (500 MHz, chloroform-d) δ 8.02 (d, J = 7.0 Hz, 2H), 7.83–7.72 (m, 2H), 7.60 (t, J = 7.3 Hz, 1H), 7.55–7.42 (m, 5H), 7.37 (s, 1H). 13C{1H} NMR (126 MHz, chloroform-d) δ 189.8, 143.3, 133.4, 130.6, 128.7, 128.7, 128.7, 127.2, 121.5. HRMS (ESI-FT-ICR) calcd. for C15H12ClO [M+H]+: 243.0577, found: 243.0569.

(Z)-3-Chloro-1-(4-nitrophenyl)-3-phenylprop-2-en-1-one (2o)[3e]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), yellow oil, 47 mg, 82% yield. 1H NMR (500 MHz, chloroform-d) 1H NMR (500 MHz, chloroform-d) δ 8.34 (d, J = 8.9 Hz, 2H), 8.14 (d, J = 8.9 Hz, 2H), 7.79 (dt, J = 6.7, 1.6 Hz, 2H), 7.61–7.41 (m, 3H), 7.37 (s, 1H). HRMS (ESI-FT-ICR) calcd. for C15H11ClNO3 [M+H]+: 288.0427, found: 288.0419.

Hydrobromination of Ynones 1

To a solution of ynone 1 (0.2 mmol) in DCM (0.5 mL) was added DMPU/HBr (60 wt/wt%) (54 mg, 0.4 mmol) at 0 °C, then the mixture was warmed to room temperature and was stirred for 8 h. After completion, the solvent was evaporated under the reduced pressure and the residue was purified by silica gel column chromatography (hexanes/EtOAc as elute solvent) to afford the corresponding products 3.

(Z)-4-Bromo-4-phenylbut-3-en-2-one (3a)[23]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:25), pale yellow oil, 33.8 mg, 76% yield. 1H NMR (400 MHz, chloroform-d) δ 7.62 (dd, J = 7.0, 2.6 Hz, 2H), 7.45–7.29 (m, 3H), 6.99 (s, 1H), 2.43 (s, 3H).13C{1H} NMR (100 MHz, chloroform-d) δ 196.68, 139.30, 133.99, 130.44, 128.55, 128.26, 128.14, 127.90, 31.77.

(Z)-1-Bromo-4,4-dimethyl-1-phenylpent-1-en-3-one (3b)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:25), yellow oil, 43 mg, 81% yield. 1H NMR (500 MHz, chloroform-d) δ 7.73–7.54 (m, 2H), 7.43–7.40 (m, 3H), 7.24 (s, 1H), 1.24 (s, 9H). 13C{1H} NMR (126 MHz, chloroform-d) δ 204.10, 139.83, 134.18, 130.16, 128.52, 128.10, 124.01, 44.38, 26.27. HRMS (ESI-FT-ICR) calcd. for C13H16BrO [M+H]+: 267.0385, found: 267.0378.

(Z)-3-Bromo-1-cyclohexyl-3-phenylprop-2-en-1-one (3c)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:25), yellow oil, 46.1 mg, 79% yield. 1H NMR (500 MHz, chloroform-d) δ 7.74–7.57 (m, 2H), 7.52–7.30 (m, 3H), 7.07 (s, 1H), 2.57–2.52 (m, 1H), 2.06–1.90 (m, 2H), 1.85–1.82 (m, 2H), 1.74–1.63 (m, 1H), 1.54–1.11 (m, 5H). 13C{1H} NMR (126 MHz, chloroform-d) δ 201.9, 139.6, 133.6, 130.2, 128.5, 128.1, 126.4, 51.7, 28.3, 25.9, 25.6. HRMS (ESI-FT-ICR) calcd. for C15H18BrO [M+H]+: 293.0541, found: 293.0534.

(Z)-1-Bromo-1-phenyloct-1-en-3-one (3d)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:25), yellow oil, 44.8 mg, 80% yield. 1H NMR (500 MHz, chloroform-d) δ 7.80–7.54 (m, 2H), 7.46–7.31 (m, 3H), 7.01 (s, 1H), 2.66 (t, J = 7.4 Hz, 2H), 1.70–1.68 (m, 2H), 1.50–1.20 (m, 4H), 0.92 (t, J = 7.0 Hz, 3H). 13C{1H} NMR (126 MHz, chloroform-d) δ 199.2, 139.5, 133.3, 130.3, 128.5, 128.1, 127.2, 44.4, 31.4, 23.6, 22.5, 13.9. HRMS (ESI-FT-ICR) calcd. for C14H18BrO [M+H]+: 281.0541, found:281.0535.

Methyl (Z)-3-(1-Bromo-3-oxooct-1-en-1-yl)benzoate (3e)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), yellow oil, 54.7 mg, 81% yield. 1H NMR (500 MHz, chloroform-d) δ 8.26 (s, 1H), 8.06 (d, J = 8.2 Hz, 1H), 7.82 (d, J = 7.8 Hz, 1H), 7.48 (t, J = 7.8 Hz, 1H), 7.05 (s, 1H), 3.94 (s, 3H), 2.66 (t, J = 7.3 Hz, 2H), 1.86–1.52 (m, 2H), 1.34 (dt, J = 7.7, 3.6 Hz, 4H), 0.90 (t, J = 6.8 Hz, 3H). 13C{1H} NMR (126 MHz, chloroform-d) δ 199.0, 166.2, 139.8, 132.5, 131.7, 131.1, 130.6, 128.9, 128.8, 128.0, 52.4, 44.4, 31.3, 23.5, 22.5, 13.9. HRMS (ESI-FT-ICR) calcd. for C16H20BrO3 [M+H]+: 339.0596, found:339.0589.

(Z)-4-(4-Acetylphenyl)-4-bromobut-3-en-2-one (3f)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:10), yellow oil, 42.5 mg, 80% yield. 1H NMR (500 MHz, chloroform-d) δ 197.05, 196.47, 143.34, 138.15, 131.97, 129.30, 128.45, 128.36, 31.66, 26.73. 13C{1H} NMR (126 MHz, chloroform-d) δ 197.1, 196.5, 143.3, 138.2, 132.0, 129.3, 128.5, 128.4, 31.7, 26.7. HRMS (ESI-FT-ICR) calcd. for C12H12BrO2 [M+H]+: 267.0012, found: 267.0014.

(Z)-4-Bromo-4-(4-bromophenyl)but-3-en-2-one (3g)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow oil, 43.3 mg, 72% yield. 1H NMR (500 MHz, chloroform-d) δ 7.54 (d, J = 8.3 Hz, 2H), 7.50 (d, J = 8.7 Hz, 2H), 6.98 (s, 1H), 2.44 (s, 3H). 13C{1H} NMR (126 MHz, chloroform-d) δ 196.4, 138.2, 132.4, 131.8, 129.6, 128.2, 124.9, 31.7. HRMS (ESI-FT-ICR) calcd. for C10H9Br2O [M+H]+: 302.9015, found:302.9013.

(Z)-4-Bromo-4-(3-methoxyphenyl)but-3-en-2-one (3h)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), yellow oil, 24.9 mg, 49% yield. 1H NMR (500 MHz, chloroform-d) δ 7.30 (d, J = 7.8 Hz, 2H), 7.21 (d, J = 7.7 Hz, 2H), 7.16 (s, 1H), 7.00 (s, 1H), 6.96 (d, J = 8.2 Hz, 2H), 3.85 (s, 3H), 2.45 (s, 3H).13C{1H} NMR (126 MHz, chloroform-d) δ 196.7, 159.5, 140.7, 133.6, 129.5, 128.1, 120.4, 116.0, 113.9, 55.4, 31.7. HRMS (ESI-FT-ICR) calcd. for C11H12BrO2 [M+H]+: 255.0021, found: 255.0013.

Methyl (Z)-3-(1-Bromo-3-oxobut-1-en-1-yl)benzoate (3i)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), yellow oil, 44.9 mg, 80% yield. 1H NMR (500 MHz, chloroform-d) δ 8.27 (s, 1H), 8.07 (d, J = 7.8 Hz, 1H), 7.83 (d, J = 7.5 Hz, 1H), 7.49 (t, J = 7.8 Hz, 1H), 7.05 (s, 1H), 3.95 (s, 3H), 2.45 (s, 3H). 13C{1H} NMR (126 MHz, chloroform-d) δ 196.4, 166.2, 139.7, 132.5, 132.4, 131.3, 130.6, 129.0, 128.8, 128.7, 52.4, 31.7. HRMS (ESI-FT-ICR) calcd. for C12H12BrO3 [M+H]+: 282.9970, found: 282.9963.

(Z)-3-Bromo-1-(4-nitrophenyl)-3-phenylprop-2-en-1-one (3j)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow oil, 51.5 mg, 78% yield. 1H NMR (500 MHz, chloroform-d) δ 8.35 (d, J = 8.9 Hz, 2H), 8.16 (d, J = 8.9 Hz, 2H), 7.79–7.68 (m, 2H), 7.55 (s, 1H), 7.51–7.43 (m, 3H). 13C{1H} NMR (126 MHz, chloroform-d) δ 188.6, 150.4, 142.04, 138.79, 137.17, 130.91, 129.66, 128.11, 124.15, 123.98. HRMS (ESI-FT-ICR) calcd. for C15H11BrNO3 [M+H]+: 331.9922, found: 331.9914.

Hydrobromination of Ynamides 4

To a solution of ynamides 4 (0.2 mmol) in DCM (0.5 mL) was added DMPU/HBr (60 wt/wt%) (54 mg, 0.4 mmol) at 0 °C, then the mixture was warmed to room temperature and was stirred for 8 h. After completion, the solvent was evaporated under the reduced pressure and the residue was purified by silica gel column chromatography (hexanes/EtOAc as elute solvent) to afford the corresponding products 5.

(E)-N-Benzyl-N-(1-bromo-2-phenylvinyl)-4-methylbenzenesulfonamide (5a)[1]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), white solid, 72.4 mg, 82% yield. Mp 142–143 °C. 1H NMR (400 MHz, chloroform-d) δ 7.86 (d, J = 8.1 Hz, 2H), 7.34 (d, J = 8.1 Hz, 2H), 7.33–7.27 (m, 2H), 7.24 (dd, J = 6.2, 1.9 Hz, 2H), 7.23–7.04 (m, 6H), 6.81 (s, 1H), 4.83 (d, J = 13.1 Hz, 1H), 3.94 (d, J = 13.1 Hz, 1H), 2.46 (s, 3H). 13C{1H} NMR (100 MHz,) δ 144.7, 139.7, 134.3, 133.6, 133.2, 129.9, 129.6, 129.2, 128.7, 128.6, 128.3, 128.1, 128.0, 119.6, 53.3, 21.7.

(E)-N-(1-Bromo-2-phenylvinyl)-N-heptyl-4-methylbenzenesulfonamide (5b)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:25), pale yellow oil, 85 mg, 86% yield. 1H NMR (400 MHz, chloroform-d) δ 7.82 (d, J = 8.2 Hz, 2H), 7.76–7.61 (m, 2H), 7.66–7.23 (m, 5H), 6.98 (s, 1H), 3.62–3.59 (m, 1H), 2.89–2.87 (m, 1H), 2.44 (s, 3H), 1.77–1.35 (m, 2H), 1.35–0.93 (m, 8H), 0.82 (t, J = 7.0 Hz, 3H). 13C{1H} NMR (100 MHz,) δ 144.6, 139.0, 134.0, 133.8, 129.4, 129.2, 129.0, 120.2, 49.7, 31.6, 28.8, 27.4, 26.9, 22.5, 21.7, 14.0. HRMS (ESI-FT-ICR) calcd. for C22H29BrNO2S [M+H]+: 450.1102, found: 450.1099.

(E)-N-(1-Bromo-2-phenylvinyl)-N-methylmethanesulfonamide (5c)[10]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), pale yellow solid, 49 mg, 85% yield. Mp 90–92 °C. 1H NMR (400 MHz, chloroform-d) δ 7.8–7.4 (m, 2H), 7.36–7.31 (m, 3H), 6.9 (s, 1H), 3.1 (s, 3H), 3.0 (s, 3H). 13C{1H} NMR (100 MHz,) δ 137.3, 133.4, 129.2, 128.8, 128.6, 120.5, 37.4, 36.5.HRMS (ESI-FT-ICR) calcd. for C10H13BrNO2S [M+H]+: 289.9850, found: 289.9842.

(E)-N-(1-Bromo-2-phenylvinyl)-N-phenylmethanesulfonamide (5d)[10]

White solid, 58 mg, 83% yield. Mp 136–137 °C. 1H NMR (400 MHz, chloroform-d) δ 8.03–7.36 (m, 4H), 7.54–7.14 (m, 6H), 7.06 (s, 1H), 3.14 (s, 3H). 13C{1H} NMR (100 MHz,) δ 138.9, 138.5, 133.3, 128.7, 128.6, 127.4, 123.7, 117.9, 39.0. HRMS (ESI-FT-ICR) calcd. for C15H15BrNO2S [M+H]+: 352.0007, found: 352.0001.

(E)-N-(1-Bromo-2-(2-chlorophenyl)vinyl)-N,4-dimethylbenzenesulfonamide (5e)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow solid, 62 mg,78% yield. Mp 82–83 °C. 1H NMR (400 MHz, chloroform-d) δ 7.80 (dd, J = 6.7, 2.8 Hz, 1H), 7.71 (dd, J = 8.4, 1.6 Hz, 2H), 7.43–7.29 (m, 1H), 7.26 (dd, J = 7.2, 3.4 Hz, 4H), 7.17 (s, 1H), 2.95 (s, 3H), 2.42 (s, 3H). 13C{1H} NMR (100 MHz,) δ 144.6, 133.5, 133.4, 133.3, 132.3, 129.6, 129.5, 126.9, 123.5, 36.9, 21.6. HRMS (ESI +) calcd. for C16H16BrClNO2S[M+H]+: 399.9774, found: 399.9770.

(E)-N-(1-Bromo-2-(3-chlorophenyl)vinyl)-N,4-dimethylbenzenesulfonamide (5f)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), white solid, 65.2 mg, 82% yield. Mp 113–114 °C. 1H NMR (400 MHz, chloroform-d) δ 7.83–7.67 (m, 2H), 7.50 (s, 1H), 7.46 (s, 1H), 7.28 (t, J = 6.5 Hz, 4H), 6.79 (d, J = 2.0 Hz, 1H), 2.98 (s, 3H), 2.43 (s, 3H). 13C{1H} NMR (100 MHz,) δ 144.6, 133.5, 133.4, 133.5, 132.3, 129.6, 129.5, 126.9, 123.5, 36.9, 21.6. HRMS (ESI-FT-ICR) calcd. for C16H16BrClNO2S [M+H]+: 399.9774, found: 399.9766.

(E)-N-(1-Bromo-2-(4-chlorophenyl)vinyl)-N,4-dimethylbenzenesulfonamide (5g)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow solid, 62.8 mg, 79% yield. Mp 142–143 °C. 1H NMR (400 MHz, chloroform-d) δ 7.76 (d, J = 8.3 Hz, 2H), 7.52 (d, J = 8.6 Hz, 2H), 7.33–7.27 (m, 4H), 6.59 (s, 1H), 3.02 (s, 3H), 2.44 (s, 3H).13C{1H} NMR (100 MHz,) δ 144.6, 134.5, 134.1, 131.6, 131.1, 129.9, 129.5, 128.9, 128.7, 35.7, 21.6. HRMS (ESI-FT-ICR) calcd. for C16H16BrClNO2S [M+H]+: 399.9774, found: 399.9764.

(E)-N-(1-Bromo-2-(4-fluorophenyl)vinyl)-N,4-dimethylbenzenesulfonamide (5h)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), white solid, 62.6 mg, 82% yield. Mp 86–88 °C. 1H NMR (400 MHz, chloroform-d) δ 7.77 (d, J = 7.7 Hz, 2H), 7.67–7.51 (m, 2H), 7.30 (d, J = 7.9 Hz, 2H), 7.03 (t, J = 8.3 Hz, 2H), 6.81 (s, 1H), 2.97 (s, 3H), 2.43 (s, 3H).19F NMR (376 MHz, chloroform-d) δ −111.2 (dq, J = 9.0, 5.0, 4.3 Hz). 13C{1H} NMR (100 MHz, chloroform-d) δ 162.7 (d, J = 250.0 Hz), 144.7, 135.8, 133.5, 130.7, 130.6, 129.5, 129.0, 121.1, 115.7 (d, J = 21.7 Hz), 36.6, 21.6. HRMS (ESI-FT-ICR) calcd. for C16H16BrFNO2S [M+H]+: 384.0069, found: 384.0061.

(E)-N-(1-Bromo-2-(4-bromophenyl)vinyl)-N-phenylmethanesulfonamide (5i)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), white solid, 69 mg, 81% yield. Mp 121–122 °C. 1H NMR (400 MHz, chloroform-d) δ 7.53 (d, J = 8.1 Hz, 2H), 7.44 (q, J = 8.4 Hz, 4H), 7.35 (t, J = 7.6 Hz, 2H), 7.29 (d, J = 6.6 Hz, 2H), 6.99 (s, 1H), 3.14 (s, 3H).13C{1H} NMR (100 MHz,) δ 138.7, 137.3, 132.2, 131.9, 130.1, 129.6, 127.6, 123.6, 123.3, 118.6, 39.0. HRMS (ESI-FT-ICR) calcd. for C15H14Br2NO2S [M+H]+: 429.9107, found: 429.9100.

(E)-N-(1-Bromo-2-(4-cyanophenyl)vinyl)-N,4-dimethylbenzenesulfonamide (5j)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), colorless oil, 64 mg, 82% yield. Mp 131–134 °C. 1H NMR (400 MHz, chloroform-d) δ δ 7.75 (d, J = 7.7 Hz, 2H), 7.68 (d, J = 8.0 Hz, 2H), 7.62 (d, J = 7.9 Hz, 2H), 7.31 (d, J = 7.8 Hz, 2H), 6.87 (s, 1H), 2.98 (s, 3H), 2.44 (s, 3H). 13C{1H} NMR (100 MHz,) δ 145.1, 138.2, 135.1, 133.1, 132.4, 129.6, 129.1, 129.0, 124.9, 118.6, 112.0, 36.8, 21.7. HRMS (ESI-FT-ICR) calcd. for C17H16BrN2O2S [M+H]+: 391.0116, found: 391.0106.

Methyl (E)-3-(2-Bromo-2-(N-phenylmethylsulfonamido)vinyl) benzoate (5k)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), colorless oil, 52.4 mg, 64% yield. 1H NMR (400 MHz, chloroform-d) δ 8.15 (s, 1H), 7.97 (d, J = 6.8 Hz, 1H), 7.85 (d, J = 8.1 Hz, 1H), 7.57 (d, J = 8.1 Hz, 2H), 7.43 (t, J = 7.8 Hz, 1H), 7.34 (t, J = 7.6 Hz, 2H), 7.28 (d, J = 7.1 Hz, 1H), 7.08 (s, 1H), 3.90 (s, 3H), 3.13 (s, 3H). 13C{1H} NMR (100 MHz,) δ 166.5, 138.9, 137.2, 133.6, 132.5, 130.5, 130.0, 129.9, 129.6, 128.9, 127.7, 124.0, 119.3, 52.2, 39.0. HRMS (ESI-FT-ICR) calcd. for C17H17BrNO4S [M+H]+: 410.0062, found: 410.0054.

Hydrochlorination of Ynamides 4

To a solution of ynamides 4 (0.2 mmol) in DCM (0.5 mL) was added DMPU/HCl (43 wt/wt%) (34 mg, 0.4 mmol) at 0 °C, then the mixture was warmed to room temperature and was stirred for 8 h. After completion, the solvent was evaporated under the reduced pressure and the residue was purified by silica gel column chromatography (hexanes/EtOAc as elute solvent) to afford the corresponding products 6.

(E)-N-(1-Chloro-2-phenylvinyl)-N-methylmethanesulfonamide (6a)[10]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), white solid, 46.5 mg, 95% yield. 1H NMR (400 MHz, chloroform-d) δ 7.56 (d, J = 7.0 Hz, 2H), 7.34–7.30 (m, 3H), 6.68 (s, 1H), 3.13 (s, 3H), 3.00 (s, 3H).13C{1H} NMR (100 MHz,) δ 132.7, 132.5, 129.1, 128.8, 128.6, 38.1, 35.7. HRMS (ESI-FT-ICR) calcd. for C10H13ClNO2S [M+H]+: 246.0356, found: 246.0350.

(E)-N-(1-Chloro-2-phenylvinyl)-N-heptyl-4-methylbenzenesulfonamide (6b)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), colorless oil, 72.9 mg, 85% yield. 1H NMR (400 MHz, chloroform-d) δ 7.81 (d, J = 8.3 Hz, 2H), 7.70 (d, J = 7.1 Hz, 2H), 7.34–7.30 (m, 5H), 6.77 (s, 1H), 3.56 (s, 1H), 3.01 (s, 1H), 2.43 (s, 3H), 1.53 (bs, 2H), 1.55–0.94 (m, 8H), 0.82 (t, J = 7.0 Hz, 3H).. 13C{1H} NMR (100 MHz,) δ 144.4, 134.7, 134.4, 133.1, 129.5, 129.1, 129.0, 128.9, 128.5, 127.9, 48.6, 31.6, 28.8, 27.3, 26.8, 22.4, 21.6, 14.0. HRMS (ESI-FT-ICR) calcd. for C22H28ClNO2S [M+H]+: 406.1608, found: 406.1599.

(E)-N-Benzyl-N-(1-chloro-2-phenylvinyl)-4-methylbenzenesulfonamide (6c)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), white solid, 74.6 mg, 94% yield. Mp 127–129 °C. 1H NMR (400 MHz, chloroform-d) δ 7.86 (d, J = 8.3 Hz, 2H), 7.42–7.28 (m, 4H), 7.24–7.00 (m, 8H), 6.60 (s, 1H), 4.80 (d, J = 12.3 Hz, 1H), 4.04 (d, J = 12.3 Hz, 1H), 2.46 (s, 3H). 13C{1H} NMR (100 MHz,) δ 144.6, 135.0, 134.9, 133.3, 132.8, 129.8, 129.6, 128.9, 128.7, 128.5, 128.3, 128.2, 128.0, 127.5, 52.4, 21.7. HRMS (ESI-FT-ICR) calcd. for C22H21ClNO2S [M+H]+: 398.0982, found: 398.0980.

(E)-N-(1-Chloro-2-phenylvinyl)-N-phenylmethanesulfonamide (6d)[10]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), pale yellow liquid, 60.1 mg, 95% yield. 1H NMR (400 MHz, chloroform-d) δ 7.83–7.41 (m, 4H), 7.46–7.07 (m, 6H), 6.84 (s, 1H), 3.13 (s, 3H).13C{1H} NMR (100 MHz,) δ 138.8, 133.6, 132.6, 129.5, 129.1, 128.7, 128.6, 128.1, 127.6, 124.3, 39.6. HRMS (ESI-FT-ICR) calcd. for C15H15ClNO2S [M+H]+: 308.0512, found: 308.0506.

(E)-N-Allyl-N-(1-chloro-2-phenylvinyl)-4-methylbenzenesulfonamide (6e)[10]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), yellow solid, 66 mg, 95% yield. 1H NMR (400 MHz, chloroform-d) δ 7.81 (d, J = 8.3 Hz, 2H), 7.67 (d, J = 7.1 Hz, 2H), 7.50–7.18 (m, 5H), 6.74 (s, 1H), 5.72–5.71 (m, 1H), 5.24–5.23 (m, 1H), 5.12–5.10 (m, 1H), 4.28 (s, 1H), 3.64 (s, 1H), 2.44 (s, 3H). 13C{1H} NMR (100 MHz,) δ 144.5, 134.7, 134.4, 133.2, 130.5, 129.5, 129.0, 128.7, 128.8, 128.5, 127.6, 120.9, 51.5, 21.6. HRMS (ESI-FT-ICR) calcd. for C18H19ClNO2S [M+H]+: 348.0825, found: 348.0817.

(E)-N-(1-Chloro-2-phenylvinyl)-N-(2-(cyclohex-1-en-1-yl)ethyl)-4-methylbenzenesulfonamide (6f)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:25), yellow oil, 68 mg, 82% yield. 1H NMR (400 MHz, chloroform-d) δ 7.81 (d, J = 8.3 Hz, 2H), 7.69 (d, J = 7.4 Hz, 2H), 7.43–7.26 (m, 5H), 6.76 (s, 1H), 5.33 (s, 1H), 3.71 (s, 1H), 3.05 (s, 1H), 2.43 (s, 3H), 2.18–2.15 (m, 2H), 1.86–1.83 (m, 4H), 1.52–1.49 (m, 4H). 13C{1H} NMR (100 MHz,) δ 144.4, 134.7, 134.5, 133.4, 133.1, 129.5, 129.3, 128.8, 128.4, 127.6, 123.9, 47.1, 35.6, 28.1, 25.1, 22.7, 22.1, 21.6. HRMS (ESI +) calcd. for C23H27ClNO2S [M+H]+: 416.1446, found: 416.1441.

(E)-3-(1-Chloro-2-phenylvinyl)oxazolidin-2-one (6g)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:10), white solid, 41 mg, 92% yield. Mp 124–126 °C. 1H NMR (400 MHz, chloroform-d) 7.31 (s, 5H), 6.73 (s, 1H), 4.42 (t, J = 7.8 Hz, 2H), 3.76 (t, J = 7.9 Hz, 2H).13C{1H} NMR (100 MHz,) δ 155.3, 132.9, 130.4, 128.8, 128.7, 127.9, 125.9, 62.8, 44.5. HRMS (ESI-FT-ICR) calcd. for C11H11ClNO2 [M+H]+: 224.0448, found: 224.0441.

(E)-N-(1-Chloro-2-(naphthalen-1-yl)vinyl)-N-methylmethanesulfonamide (6h)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), pale yellow liquid, 53 mg, 90% yield. 1H NMR (400 MHz, chloroform-d) δ 7.94 (d, J = 7.6 Hz, 1H), 7.84 (t, J = 9.2 Hz, 2H), 7.76 (d, J = 7.2 Hz, 1H), 7.62–7.43 (m, 3H), 7.32 (s, 1H), 3.02 (s, 3H), 2.81 (s, 3H). 13C{1H} NMR (100 MHz,) δ 133.4, 131.5, 131.2, 130.1, 130.0, 129.1, 128.7, 126.6, 126.5, 126.1, 125.6, 123.8, 38.5, 36.3. HRMS (ESI-FT-ICR) calcd. for C14H15ClNO2S [M+H]+: 296.0512, found: 296.0506.

(E)-N-(1-Chloro-2-(4-fluorophenyl)vinyl)-N,4-dimethylbenzenesulfonamide (6i)[24]

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), pale yellow solid, 63.7 mg, 94% yield. 1H NMR (400 MHz, chloroform-d) δ 7.77 (d, J = 8.1 Hz, 2H), 7.64–7.54 (m, 2H), 7.30 (d, J = 7.9 Hz, 2H), 7.09–6.99 (m, 2H), 6.60 (s, 1H), 3.01 (s, 3H), 2.43 (s, 3H). 19F NMR (376 MHz, chloroform-d) δ −111.5 – −111.6 (m). 13C{1H} NMR (100 MHz, chloroform-d) δ 162.7 (d, J = 249.7 Hz), 144.6, 134.1, 131.1, 130.6 (d, J = 8.3 Hz), 129.5, 129.3, 128.8, 115.7 (d, J = 21.7 Hz), 35.7, 21.6.

(E)-N-(1-Chloro-2-(4-chlorophenyl)vinyl)-N-4-dimethylbenzenesulfonamide (6j)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), white solid, 61.7 mg, 87% yield. Mp 108–110 °C. 1H NMR (400 MHz, chloroform-d) δ 7.76 (d, J = 7.9 Hz, 2H), 7.52 (d, J = 7.5 Hz, 2H), 7.30 (d, J = 7.6 Hz, 4H), 6.80 (s, 1H), 2.97 (s, 3H), 2.44 (s, 3H). 13C{1H} NMR (100 MHz,) δ 144.8, 135.7, 134.6, 133.5, 132.3, 129.9, 129.5, 129.0, 128.9, 122.0, 36.7, 21.6. HRMS (ESI-FT-ICR) calcd. for C16H16Cl2NO2S [M+H]+: 356.0279, found:356.0272.

(E)-N-(1-Chloro-2-(4-methoxyphenyl)vinyl)-N-methylmethanesulfonamide (6k)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), white solid, 50.6 mg, 92% yield. Mp 125–127 °C 1H NMR (500 MHz, chloroform-d) δ 7.54 (d, J = 8.7 Hz, 2H), 6.89 (d, J = 8.7 Hz, 2H), 6.62 (s, 1H), 3.81 (s, 3H), 3.14 (s, 3H), 3.03 (s, 3H).13C{1H} NMR (125 MHz,) δ 160.1, 132.0, 130.2, 126.9, 125.4, 114.1, 55.3, 38.0, 35.6. HRMS (ESI-FT-ICR) calcd. for C11H15ClNO3S [M+H]+: 276.0461, found:276.0453.

(E)-N-(1-Chloro-2-(4-nitrophenyl)vinyl)-N-4-dimethylbenzenesulfonamide (6l)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), white solid, 64.4 mg, 88% yield. Mp 154–157 °C. 1H NMR (500 MHz, chloroform-d) δ 8.21 (d, J = 8.9 Hz, 2H), 7.77 (d, J = 7.5 Hz, 4H), 7.33 (d, J = 8.4 Hz, 2H), 3.06 (s, 3H), 2.46 (s, 3H). 13C{1H} NMR (126 MHz,) δ 147.3, 145.0, 139.6, 133.7, 133.6, 130.1, 129.7, 129.4, 128.7, 123.9, 35.8, 21.6. HRMS (ESI-FT-ICR) calcd. for C16H16ClN2O4S [M+H]+: 367.0519, found 367.0512.

(E)-N-(2-(4-Acetylphenyl)-1-chlorovinyl)-N-4-dimethylbenzenesulfonamide (6m)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:10), white solid, 66 mg, 91% yield. Mp 142–143 °C. 1H NMR (400 MHz, chloroform-d) δ δ 7.93 (d, J = 8.4 Hz, 2H), 7.75 (d, J = 8.1 Hz, 2H), 7.67 (d, J = 7.9 Hz, 2H), 7.30 (d, J = 7.8 Hz, 2H), 6.68 (s, 1H), 3.03 (s, 3H), 2.59 (s, 3H), 2.42 (s, 3H). 13C{1H} NMR (100 MHz,) δ 197.3, 144.7, 137.7, 136.7, 133.9, 132.1, 131.2, 129.6, 128.8, 128.7, 128.6, 35.6, 26.6, 21.6. HRMS (ESI-FT-ICR) calcd. for C18H19ClNO3S [M+H]+: 364.0774, found: 364.0766.

(E)-N-(1-Chloro-2-(thiophen-3-yl)vinyl)-N,4-dimethylbenzenesulfonamide (6n)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:15), white solid, 58.8 mg, 90% yield. Mp 139–141 °C. 1H NMR (500 MHz, chloroform-d) δ 7.84 (d, J = 6.8 Hz, 2H), 7.38 (d, J = 4.4 Hz, 1H), 7.34 (d, J = 7.7 Hz, 2H), 7.15 (d, J = 3.5 Hz, 1H), 7.00 (t, J = 3.9 Hz, 1H), 6.88 (s, 1H), 3.05 (s, 3H), 2.46 (s, 3H). 13C{1H} NMR (126 MHz,) δ 144.6, 135.9, 134.1, 129.9, 129.5, 129.1, 128.3, 127.0, 126.7, 126.4, 35.5, 21.7. HRMS (ESI-FT-ICR) calcd. for C14H15ClNO2S2 [M+H]+: 328.0233, found: 328.0225.

(3S,10R,13R,17R)-10,13-Dimethyl-17-((R)-6-methylheptan-2-yl)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-3-yl (E)-6-chloro-6-((N,4-dimethylphenyl)sulfonamido)hex-5-enoate (6o)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:20), white solid, 114 mg, 82% yield. Mp 88–89 °C. 1H NMR (500 MHz, chloroform-d δ 7.76 (d, J = 8.2 Hz, 2H), 7.32 (d, J = 8.0 Hz, 2H), 5.79 (t, J = 7.5 Hz, 1H), 5.38 (d, J = 5.1 Hz, 1H), 4.64 (dq, J = 11.9, 7.0, 5.6 Hz, 1H), 2.92 (s, 3H), 2.44 (s, 3H), 2.36–2.32 (m, 6H), 2.05–1.93 (m, 2H), 1.92–1.79 (m, 3H), 1.68–1.06 (m, 23H), 1.03 (s, 3H), 0.92 (d, J = 6.5 Hz, 3H), 0.88 (d, J = 2.3 Hz, 3H), 0.87 (d, J = 2.3 Hz, 3H), 0.68 (s, 3H).13C{1H} NMR (126 MHz,) δ 172.6, 144.3, 139.7, 134.3, 134.0, 129.5, 129.0, 128.5, 122.6, 74.0, 56.7, 56.1, 50.0, 42.3, 39.7, 39.5, 38.1, 37.0, 36.6, 36.2, 35.9, 35.8, 34.1, 31.9, 31.9, 28.6, 28.2, 28.0, 27.8, 24.3, 23.9, 23.8, 22.8, 22.6, 21.6, 21.0, 19.3, 18.7. HRMS (ESI-FT-ICR) calcd. for C41H63ClNO4S [M+H]+: 700.4166, found: 700.4158.

Further Transformations of Halogenated Alkene Products

A mixture of 2a (0.2 mmol), phenylboronic acid (36.5 mg, 0.3 mmol), Pd(PPh3)2Cl2 (7 mg, 5 mol %), and Cs2CO3 (652 mg, 2 mmol) was added 1,4-dioxane/H2O (4/1, 2 mL) heated at 60 °C for 8 h. After the completion of the reaction, the reaction mixture extracted with EtOAc, the combined organic layers dried over Na2SO4 and removal of the solvent by rotary evaporation the resulting residue was purified by chromatography on silica gel to give the desired products.

4,4-Diphenylbut-3-en-2-one (7a)[25]

1H NMR (400 MHz, chloroform-d) δ 7.50–7.36 (m, 3H), 7.39–7.27 (m, 5H), 7.23–7.18 (m, 1H), 6.58 (s, 1H), 1.88 (s, 3H).13C{1H} NMR (100 MHz, chloroform-d) δ 200.2, 154.0, 140.8, 138.9, 129.6, 129.5, 128.8, 128.4, 128.4, 127.7, 30.3.

A mixture of 4a (73.5 mg, 0.3 mmol), phenylboronic acid (51.2 mg, 4.2 mmol), Pd(OAc)2 (7 mg, 10 mol %), and K2CO3 (82.8 mg, 0.6 mmol) in EtOH/H2O (4/1) (2 mL) was heated at 80 °C for 8 h. After the completion of the reaction, the reaction mixture was filtered through a pad of Celite and removal of the solvent in vacuum to give the crude product. The resulting residue was purified by silica gel chromatography to give the desired products.

(Z)-N-(1,2-Diphenylvinyl)-N-methylmethanesulfonamide (Z-8a)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:40), colorless oil, 40.2 mg, 47% yield. 1H NMR (500 MHz, chloroform-d) δ 7.57 (d, J = 8.8 Hz, 2H), 7.52 (d, J = 7.2 Hz, 2H), 7.45–7.41 (m, 5H), 7.33 (d, J = 7.4 Hz, 1H), 6.83 (s, 1H), 3.12 (s, 3H), 2.50 (s, 3H). 13C{1H} NMR (126 MHz,) δ 139.6, 137.7, 135.7, 128.9, 128.8, 128.7, 128.7, 128.1, 127.0, 40.0, 37.1. HRMS (ESI-FT-ICR) calcd. for C16H17NO2S [M+H]+: 288.1058, found: 288.1050.

(E)-N-(1,2-Diphenylvinyl)-N-methylmethanesulfonamide (E-8a)

Purified by flash column chromatography (ethyl acetate/hexanes = 1:40), white solid, 37.2 mg, 43% yield. Mp 113–115 °C 1H NMR (500 MHz, chloroform-d) δ 7.37 (dd, J = 7.1, 2.8 Hz, 2H), 7.32 (dd, J = 5.2, 1.9 Hz, 3H), 7.16–7.12 (m, 3H), 7.06–6.98 (m, 2H), 6.75 (s, 1H), 3.13 (s, 3H), 2.99 (s, 3H). 13C{1H} NMR (125 MHz,) δ 140.0, 135.4, 135.2, 129.8, 129.2, 128.8, 128.7, 128.1, 127.5, 127.3, 39.2, 37.1. HRMS (ESI-FT-ICR) calcd. for C16H18NO2S [M+H]+: 288.1058, found: 288.1051.

A mixture of 5c (87 mg, 0.3 mmol), ethynyltrimethylsilane (41.2 mg, 4.2 mmol), Pd(PPh3)Cl2 (10 mg, 5 mol %), and CuI (5 mg, 8 mol %) in Et3N/THF (1/1; 1.5 mL) was stirred at room temperature for 8 h. After the completion of the reaction, the reaction mixture was filtered through Celite and removal of the solvent in vacuum gave the crude product. The crude product was purified by silica gel chromatography (ethyl acetate/hexanes = 1:30) to give the desired product 9a as a pale-yellow oil (87 mg, 95% yield). Major isomer: 1H NMR (400 MHz, chloroform-d) δ 7.84 (dd, J = 7.6, 2.0 Hz, 2H), 7.42–7.27 (m, 3H), 7.05 (s, 1H), 3.12 (s, 3H), 2.94 (s, 3H), 0.26 (s, 9H).13C{1H} NMR (125 MHz,) δ 140.3, 133.5, 129.5, 129.3, 128.3, 118.4, 104.3, 99.0, 35.7, −0.4. Minor isomer: 1H NMR (400 MHz, chloroform-d) δ 7.70 (d, J = 8.1 Hz, 2H), 6.80 (s, 1H), 3.05 (s, 3H), 3.01 (s, 3H), 0.23 (s, 8H).13C{1H} NMR (126 MHz,) δ 139.0, 133.6, 129.9, 128.7, 119.9, 101.0, 97.1, 36.4, −0.3. HRMS (ESI-FT-ICR) calcd. for C15H22NO2SSi [M+H]+: 308.1141, found: 308.1133.