Base Mediated Tandem Vinylogous Addition and Cyclization of γ-Phosphonyl/Sulfonyl Crotonates and Ynones: Synthesis of Functionalized 2-Pyrones.

A general method for highly functionalized 2-pyrones via a base-mediated sequential vinylogous addition and cyclization of γ-phosphonyl/sulfonyl crotonates and ynones are described. An exclusive E-geometry with respect to the newly generated olefin substituent at C3 of pyrone was observed. Imino glyoxalates and glycine imines similarly reacted with ynones to deliver 3-imino pyrones.

Introduction

2-Pyrone not only occurs very frequently in natural products isolated from plants, animals, marine sources, and microorganisms but also appears quite often in biologically and pharmaceutically active synthetic molecules.[1−6] A 2-pyrone skeleton with different substitution patterns is known to possess a wide range of biological activities such as antimicrobial,[2] antifungal,[3] anti-inflammatory,[4] anti-HIV,[5] and anticancer.[6] Further, with its unique electronically biased unsaturated cyclic system, it has been utilized as a versatile building block in organic synthesis especially as a diene component in Diels–Alder reactions.[7] As a result, considerable attention has been devoted to access diversely functionalized pyrone compounds by employing different methods.[8] Despite the fact that these methods made processes more facile and efficient, there still exists a vast need to develop the new methodologies to broaden the diversity of the pyrone compounds. There have been several efforts made in recent times addressing various limitations associated with traditional methods. One of the most convenient methods found in such efforts is the use of alkyne as the substrate.[9] Electrophilic iodo cyclization of yne-enoates by Yao and Larock,[9a] rhodium-catalyzed oxidative coupling of substituted acrylic acids with alkynes by Miura et al.,[9b] ruthenium-catalyzed intermolecular homo and heterodimerization of substituted propiolates by Manikandan and Jeganmohan,[9c] sequential alkyne activation of terminal alkynes and propiolic acids by gold(I) catalysts by Schreiber et al.,[9d] palladium-catalyzed one-pot regioselective 6-endo cyclization and alkylation/alkenylation of enynoates by Loh et al.,[9e,9f] and Pradasani et al.,[9g] were the prominent examples. Another interesting method is the conjugate addition and cyclization of active methylene compounds and ynones.[10] Surprisingly, the pioneering work by Baddar’s group[10a] using alkyl aryl acetates (Scheme a) has not been much elaborated to other active methylene substrates. An effort by Shimizu et al.[10b] with β-keto esters led to rearranged products (Scheme b) often as a mixture of compounds with decarboxylated congeners.

Scheme 1

Synthesis of 2-Pyrones from Ynones

Herein, as a part of our ongoing efforts of unearthing the novel reactivities of activated alkynes,[11] we describe the synthesis of uniquely functionalized 2-pyrones based on a concept of sequential allylic γ-carbon conjugate addition and cyclization of γ-phosphonyl/sulfonyl crotonates and ynones (Scheme c). Further, imino glyoxalates and glycine imines were found to similarly react with ynones to deliver 3-imino pyrones (Scheme d). This later result is quite contrasting to the findings by Deng et al.[12] to access five-membered adducts from same substrates under silver catalysis (Scheme e).

Results and Discussion

We initiated our investigation (Table ) using readily available ynone 1a and phosphonyl crotonate 2. When NaH was used as the base in dimethyl sulfoxide (DMSO), we obtained the desired product 3a but in 30% yield (entry 1). NaOH and NaOEt also afforded the desired product but in moderate yield (entry 2, 3). Other inorganic base CS2CO3 was not found to be suitable for this transformation (entry 4). Pleasingly, when KOBu was employed as the base, the product was obtained in 60% yield whereas no product was observed in the absence of the base (entry 5, 6). Other solvents like dimethylformamide (DMF), 1,4-dioxane, toluene, tetrahydrofuran (THF), and MeCN were screened with KOBu and DMF was found to be the most suitable for the transformation with a product yield of 70% (entry 7–11).

Table 1

Optimization Studiesa

entry	base	solvent	time (h)	yield (%)b
1	NaH	DMSO	2	30
2	NaOH	DMSO	2	38
3	NaOEt	DMSO	2	48
4	Cs2CO3	DMSO	2	15
5	KOtBu	DMSO	2	60
6		DMSO	2	n.r
7	KOtBu	CH3CN	2	68
8	KOtBu	DMF	1	70
9	KOtBu	1,4-dioxane	1	65
10	KOtBu	toluene	1	35
11	KOtBu	THF	1	55

Reaction conditions: 1a (0.5 mmol), 2 (1 mmol), base (1 mmol) in solvent (2.5 mL).

Isolated yield.

With the optimization conditions in hand, we set out to investigate the generality of this vinylogous Michael addition and concomitant cyclization reaction with various ynones and initially with phosphonyl crotonate 2a as depicted in Table . At first, we investigated the reactivity against electronic variation in ynones. Like 1a, various alkylated phenyl ynones (1b–f) smoothly reacted with 2a, irrespective of the group (Me, Et, Bu, and Pent) and position (m or p), to give the corresponding products 3b–f in excellent yields of 70–76%. Higher electron rich counterparts 1g and 1h with methoxy groups at the meta or para position cleanly underwent the transformation, giving expected adducts 3g–h in anticipated products in good yields (67%). Halogenated phenyl groups with Cl, Br, and F (1i–k) smoothly underwent in standard conditions and delivered the desired products in good yields (3i–k in 68–72%) and the structure of 3i was unambiguously confirmed by X-ray crystallography. Ynones with other aryl and heteroaryl groups like naphthyl and pyridyl (1l–m) showed similar reactivity to afford the products (3l–m) with equal ease and with no loss in the geometry selectivity of the olefin substituent.

Table 2

Scope of Ynones

Setting a limitation, the aliphatic ynones 1n and 1o proved to be unproductive in the transformation (a). The extended conjugation from the aryl group to ynone thus remains essential for this transformation.

We next studied the effect of the substitution at the ketone terminus of ynone (Table ). Toluoyl ynone 1p showed excellent reactivity (3p in 77% yield) whereas electron deficient halo-aryl ynones 1q–s with F or Cl, and nitro aryl ynone 1t were found to be slightly less productive giving the corresponding products 3q–t in 61–70% yields. Further, heteroarylated (furanyl and thiophenyl) adducts 3u and 3v were smoothly obtained from relevant substrates (1u–v) in 66–69% yields.

Table 3

Scope of Ynonesa

1 (0.5 mmol) and 2 (1 mmol), base (1 mmol) in 3 mL.

Isolated yields.

Our attention was next turned to check whether sulfonyl crotonates with analogous active methylene groups participate similarly in the above transformation. Pleasingly, 4a reacted with ynone 1a smoothly under standard conditions to afford 5a in 67% yield (Table ). Geometry of the newly generated olefin tether was trans as usual and was highly exclusive and the structure was unambiguously confirmed by X-ray crystallography. The toluene sulfonyl substrate was also found to similarly participate in the addition/cyclization sequence to produce the corresponding 2-pyrones 5b in 70% yield with E-vinyl sulfonyl tether at C3.

Table 4

Scope of Sulfonyl Crotonates

We thereafter became curious to know the fate of glyoxyl benzyl imine 6 (Table ), which structurally closely resembles 2 and 4, in the above addition/cyclization sequence. They are supposed to produce 2-pyrones with iminyl substitution at C3. Gratifyingly, 1a smoothly underwent the proposed transformation with 6a to give anticipated iminyl-substituted pyrone 7a in 67% yield. Similarly, imine formed from fluoro benzyl amine 6b was found to successfully deliver the corresponding pyrone 7b in 62% yield. Steric congestion in the imines formed from secondary benzyl amines did not affect the reaction during the synthesis of pyrones 7c–f (68–72%). Structure of 7c was also further confirmed by the X-ray crystallography study.

Table 5

Scope of Benzyl Imines

Glycenimene 8 upon deprotonation is supposed to straightly give the stable carbanion stabilized by ester unlike in the above case 6 where a delocalization occurred to reach the same. Hence 8 would in principle deliver the same products (7). As expected, 8a–c when exposed to the standard conditions in the presence of ynone 1a cleanly formed the pyrones 7a–c, respectively, in 64–70% yields (Scheme ). Thus, the same products are available from either way as both the starting materials are easily accessible from commercially available chemicals unlike in the case of crotonates 2 and 4 whose other isomers are difficult to be assembled.

Scheme 2

Scope of Glycenimenes

A plausible mechanism for the γ-carbon vinylogus Michael addition/cyclization[13] of EWG tethered crotonates with ynones is depicted in Scheme . Base-mediated deprotonation of 2/4/6 gave carbanion A which is delocalized to give ester-stabilized carbanions that underwent Michael addition with ynone 1 to give B. Conjugation-based stability incurred E-geometry to the migrated olefin. Second deprotonation adjacent to the ester led to demethoxylative cyclization through C and D to afford the pyrone 3/5/7.

Scheme 3

Plausible Mechanism

In conclusion, we achieved an efficient access to novel, densely functionalized pyrones from readily available EWG attached crotonates and ynones via a base-mediated sequential vinylogus conjugate addition and concomitant cyclization. A huge variety of substrates were converted to the corresponding pyrones to show the generality of the method. Imino glyoxalates and glycine imines, having structural resemblance to these crotonates, were also shown to be successful substrates for the transformation to give 3-iminylated 2-pyrones.

Experimental Section

General Information and Methods

All reagents and solvents were purchased from commercial sources and used without purification. NMR spectra were recorded with a 300, 400, or 500 MHz spectrometer for 1H NMR, 100 or 125 MHz for 13C NMR spectroscopy. Chemical shifts are reported relative to the residual signals of tetramethylsilane in CDCl3 or deuterated solvent CDCl3 for 1H and 13C NMR spectroscopy. Multiplicities are reported as follows: singlet (s), doublet (d), doublet of doublets (dd), doublet of triplets (dt), triplet (t), quartet (q), and multiplet (m). HRMS were recorded by using a QTof or ESI mass spectrometer. Column chromatography was performed with silica gel (100–200 mesh) as the stationary phase. All reactions were monitored by using thin-layer chromatography (TLC). Characterizations of new compounds were further established by using HRMS.

General Procedure for the Preparation of Starting Materials, Final Compounds, and Chareteristic Data of Compounds

Starting materials 1,[11d]2,[13a]4,[13b] and 8,[12] were prepared in a one-step reaction, following the literature procedures.

Procedure for the Synthesis of Ethyl (R,E)-2-((1-Phenylethyl)imino)acetate (6c)

To a stirred solution of ethyl glyoxylate (1 g, 9.8 mmol, 1 equiv) in 10 mL of CHCl3 was added Na2SO4 (aprx. 2 g) at 0 °C under a N2 atmosphere followed by R-1-phenethyl amine (1.19 g, 9.8 mmol, 1 equiv) over 10 min. The resultant reaction mixture was stirred at room temperature for 30 min. Upon compilation, the solvent was removed under reduced pressure the crude material was purified on silica gel using 30% EtOAc/hexane to get 6c (1.75 mg, 85%) as pale yellow viscous liquid.

Ethyl (R,E)-2-((1-Phenylethyl)imino)acetate (6c)

mp 140–142 °C; R = 0.45 (SiO2, 30% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.65 (d, J = 0.8 Hz, 1H), 7.27 (d, J = 4.4 Hz, 4H), 7.22–7.18 (m, 1H), 4.54 (dt, J = 12.9, 6.5 Hz, 1H), 4.27 (qd, J = 7.1, 1.1 Hz, 2H), 1.55 (d, J = 6.7 Hz, 3H), 1.27 (t, J = 7.1 Hz, 3H); 13C{1H} NMR (100 MHz, CDCl3): δ 163.2, 152.3, 142.6, 128.6, 127.4, 126.8, 69.6, 61.7, 23.7, 14.1; IR (KBr): ν 3061, 3029, 2978, 1746, 1647, 1374, 1298, 1201, 1032, 701 cm–1; HRMS(ESI): calcd for C12H16NO2 [M + H]+, 206.1181; found, 206.1167.

General Procedure A for the Synthesis 2-Pyrone Derivatives (3, 5 and 7)

To a stirred solution of 2, 4, and 6 (1 mmol, 2 equiv) in 3 mL of DMF (for 4 solvent was CH3CN) was added the base (KOBu) (1 mmol, 2 equiv) and ynone (1) (0.5 mmol, 1 equiv) at room temperature. The reaction mixture was stirred at the same temperature until the complete conversion of the starting material (monitored by TLC). The reaction mixture was diluted with water and extracted with EtOAc. Combined extracts were washed with brine (10 mL) and dried over Na2SO4. After removal of the solvent under reduced pressure the crude material was purified on silica gel using EtOAc/hexanes.

(E)-Diethyl(2-(2-oxo-4,6-diphenyl-2H-pyran-3-yl)vinyl)phosphonate (3a)

It (143 mg) was obtained from 1a (103 mg, 0.5 mmol) following general procedure A. It was obtained in 70% yield as a light yellow solid; mp 140–142 °C; R = 0.56 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.92–7.87 (m, 2H), 7.54–7.46 (m, 6H), 7.38 (dd, J = 7.5, 1.9 Hz, 2H), 7.28 (d, J = 7.0 Hz, 1H), 7.23 (d, J = 1.3 Hz, 1H), 6.79 (s, 1H), 4.05 (p, J = 7.2 Hz, 4H), 1.28 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (125 MHz, CDCl3): δ 160.4, 159.2, 157.4, 139.7 (d, J = 8.45 Hz), 136.5, 131.4, 130.8, 129.9, 129.1, 129.0, 128.4, 125.9, 120.0 (d, J = 185.1 Hz), 115.6 (d, J = 22.8 Hz), 105.1, 61.7 (d, J = 5.28 Hz), 16.35 (d, J = 6.4 Hz); 31P NMR (162 MHz, CDCl3): δ 19.5; IR (KBr): ν 3066, 2984, 1713, 1492, 1228, 1030, 942, 768, 691 cm–1; HRMS(ESI): calcd for C23H24O5P [M + H]+, 411.1361; found, 411.1362.

(E)-Diethyl(2-(2-oxo-6-phenyl-4-(p-tolyl)-2H-pyran-3-yl)vinyl)phosphonate (3b)

It (161 mg) was obtained from 1b (110 mg, 0.5 mmol) following general procedure A. It was obtained in 76% yield as a light yellow solid; mp 160–162 °C; R = 0.54 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.89 (dd, J = 6.5, 3.0 Hz, 2H), 7.48 (dd, J = 5.2, 1.7 Hz, 3H), 7.33–7.23 (m, 6H), 6.79 (s, 1H), 4.06 (p, J = 7.2 Hz, 4H), 2.43 (s, 3H), 1.29 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.5, 159.0, 157.5, 140.3, 140.2 (d, J = 8.8 Hz), 133.6, 131.4, 130.8, 129.6, 129.0, 128.5, 125.9, 119.5 (d, J = 185.4 Hz), 115.4 (d, J = 22.5 Hz), 105.1, 61.7 (d, J = 5.4 Hz), 21.4, 16.3 (d, J = 6.4 Hz); 31P NMR (162 MHz, CDCl3): δ 19.7; IR (KBr): ν 3063, 2985, 1716, 1493, 1230, 1051, 939, 772 cm–1; HRMS(ESI): calcd for C24H26O5P [M + H]+, 425.1517; found, 425.1516.

(E)-Diethyl(2-(4-(4-ethylphenyl)-2-oxo-6-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3c)

It (162 mg) was obtained from 1c (117 mg, 0.5 mmol) following general procedure A. It was obtained in 74% yield as a light yellow solid; mp 165–167 °C; R = 0.54 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.84–7.79 (m, 2H), 7.40 (dd, J = 5.3, 1.9 Hz, 3H), 7.30–7.22 (m, 5H), 7.20–7.17 (m, 1H), 6.72 (s, 1H), 3.99 (p, J = 7.1 Hz, 4H), 2.65 (q, J = 7.6 Hz, 2H), 1.24–1.19 (m, 9H); 13C{1H} (100 MHz, CDCl3): δ 160.5, 159.0, 157.5, 146.5, 140.1 (d, J = 8.6 Hz), 133.8, 131.3, 130.8, 129.0, 128.6, 128.5, 125.9, 119.5 (d, J = 185.9 Hz), 115.4 (d, J = 22.5 Hz), 105.2, 61.7, (d, J = 5.4 Hz), 28.7, 16.3, (d, J = 6.4 Hz), 15.3; 31P NMR (162 MHz, CDCl3): δ 19.7; IR (KBr): ν 3064, 2975, 1712, 1493, 1245, 1025, 966, 765 cm–1; HRMS(ESI): calcd for C25H28O5P [M + H]+, 439.1674; found, 439.1680.

(E)-Diethyl(2-(2-oxo-6-phenyl-4-(m-tolyl)-2H-pyran-3-yl)vinyl)phosphonate (3d)

It (159 mg) was obtained from 1d (110 mg, 0.5 mmol) following general procedure A. It was obtained in 75% yield as a light yellow solid; mp 191–201 °C; R = 0.54 (SiO2, 70% EtOAc/hexanes); 1H NMR (500 MHz, CDCl3): δ 7.89 (dd, J = 7.5, 2.0 Hz, 2H), 7.50–7.46 (m, 3H), 7.39 (t, J = 7.5 Hz, 1H), 7.29 (d, J = 7.7 Hz, 1H), 7.26 (d, J = 3.5 Hz, 1H), 7.22 (s, 1H), 7.16 (d, J = 8.0 Hz, 1H), 6.78 (s, 1H), 4.05 (p, J = 7.2 Hz, 4H), 2.43 (s, 3H), 1.28 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.4, 159.1, 157.7, 139.9 (d, J = 8.5 Hz), 138.8, 136.5, 131.4, 130.8, 130.6, 129.0, 128.9, 128.8, 125.9, 125.6, 119.7 (d, J = 185.7 Hz), 115.6 (d, J = 22.4 Hz), 105.1, 61.7 (d, J = 5.6 Hz), 21.4, 16.3 (d, J = 6.3 Hz); 31P NMR (162 MHz, CDCl3): δ 19.6; IR (KBr): ν 3066, 2990, 1714, 1498, 1231, 1046, 944, 774 cm–1; HRMS(ESI): calcd for C24H26O5P [M + H]+, 425.1517; found, 425.1515.

(E)-Diethyl(2-(4-(4-(tert-butyl)phenyl)-2-oxo-6-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3e)

It (165 mg) was obtained from 1e (131 mg, 0.5 mmol) following general procedure A. It was obtained in 71% yield as a light yellow solid; mp 191–193 °C; R = 0.52 (SiO2, 70% EtOAc/hexanes); 1H NMR (500 MHz, CDCl3): δ 7.88 (dd, J = 7.5, 2.1 Hz, 2H), 7.54–7.51 (m, 2H), 7.47 (dd, J = 5.0, 2.3 Hz, 3H), 7.35–7.30 (m, 3H), 7.27 (d, J = 7.4 Hz, 1H), 6.79 (s, 1H), 4.06 (p, J = 7.1 Hz, 4H), 1.37 (s, 9H), 1.28 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.5, 159.0, 157.5, 153.4, 140.0 (d, J = 8.6 Hz), 133.6, 131.3, 130.8, 129.0, 128.4, 125.9, 125.9, 119.5 (d, J = 185.0 Hz), 115.4 (d, J = 22.9 Hz), 105.2, 61.7 (d, J = 5.4 Hz), 34.9, 31.2, 16.3 (d, J = 6.5 Hz). 31P NMR (162 MHz, CDCl3): δ 19.7; IR (KBr): ν 3060, 2961, 1715, 1490, 1247, 1029, 966, 769 cm–1; HRMS(ESI): calcd for C27H32O5P [M + H]+, 467.1987; found, 467.1981.

(E)-Diethyl(2-(2-oxo-4-(4-pentylphenyl)-6-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3f)

It (168 mg) was obtained from 1f (138 mg, 0.5 mmol) following general procedure A. It was obtained in 70% yield as a light yellow solid; mp 119–121 °C; R = 0.52 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.91–7.86 (m, 2H), 7.48 (dd, J = 5.2, 1.8 Hz, 3H), 7.29 (dt, J = 22.0, 5.0 Hz, 6H), 6.79 (s, 1H), 4.06 (p, J = 7.2 Hz, 4H), 2.67 (t, 2H), 1.66 (quintet, J = 7.6 Hz, 2H), 1.38–1.34 (m, J = 7.0, 3.1 Hz, 4H), 1.28 (t, J = 7.1 Hz, 3H), 0.92 (t, J = 6.7 Hz, 3H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.5, 159.0, 157.5, 145.3, 140.1 (d, J = 8.6 Hz), 133.8, 131.3, 130.8, 129.0, 129.0, 128.6, 125.9, 119.5 (d, J = 185.1 Hz), 115.3 (d, J = 23.0 Hz), 105.2, 61.7 (d, J = 5.3 Hz), 35.8, 31.5, 30.9, 22.5, 16.3 (d, J = 6.6 Hz), 14.0; 31P NMR (162 MHz, CDCl3): δ 19.7; IR (KBr): ν 3062, 2929, 1717, 1491, 1250, 1039, 956, 688 cm–1; HRMS(ESI): calcd for C28H34O5P [M + H]+, 481.2143; found, 481.2140.

(E)-Diethyl(2-(4-(4-methoxyphenyl)-2-oxo-6-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3g)

It (147 mg) was obtained from 1g (118 mg, 0.5 mmol) following general procedure A. It was obtained in 67% yield as a light yellow solid; mp 148–150 °C; R = 0.54 (SiO2, 80% EtOAc/hexanes);1H NMR (400 MHz, CDCl3): δ 7.94–7.89 (m, 2H), 7.50 (dd, J = 5.2, 1.8 Hz, 3H), 7.40–7.27 (m, 4H), 7.07–7.02 (m, 2H), 6.81 (s, 1H), 4.09 (p, J = 7.2 Hz, 4H), 3.90 (s, 3H), 1.32 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 161.1, 160.6, 159.0, 157.1, 140.4 (d, J = 8.9 Hz), 131.3, 130.9, 130.3, 129.0, 128.6, 125.9, 119.3 (d, J = 185.2 Hz), 115.0 (d, J = 22.5 Hz), 114.4, 105.1, 61.7 (d, J = 5.3 Hz), 55.4, 16.3 (d, J = 6.4 Hz); 31P NMR (162 MHz, CDCl3): δ 19.9; IR (KBr): ν 3064, 2925, 1705, 1488, 1251, 1026, 957, 761 cm–1; HRMS(ESI): calcd for C24H26O6P [M + H]+, 441.1467; found, 441.1464.

(E)-Diethyl(2-(4-(3-methoxyphenyl)-2-oxo-6-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3h)

It (147 mg) was obtained from 1h (118 mg, 0.5 mmol) following general procedure A. It was obtained in 67% yield as a light yellow solid; mp 146–148 °C; R = 0.54 (SiO2, 80% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.92–7.86 (m, 2H), 7.50–7.39 (m, 4H), 7.29 (d, J = 2.8 Hz, 1H), 7.23 (s, 1H), 7.02 (dd, J = 8.3, 1.9 Hz, 1H), 6.95 (d, J = 7.5 Hz, 1H), 6.89 (s, 1H), 6.79 (s, 1H), 4.06 (p, 4H), 3.86 (s, 3H), 1.28 (t, J = 7.0 Hz, 3H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.3, 159.8, 159.2, 157.2, 139.8 (d, J = 8.6 Hz), 137.8, 131.4, 130.8, 130.1, 129.1, 125.9, 120.7, 120.2 (d, J = 185.0 Hz), 115.7 (d, J = 22.8 Hz), 115.4, 114.1, 104.9, 61.8 (d, J = 5.5 Hz), 55.5, 16.3 (d, J = 6.3 Hz); 31P NMR (162 MHz, CDCl3): δ 19.5; IR (KBr): ν 3455, 2985, 1723, 1440, 1252, 1026, 968, 790 cm–1; HRMS(ESI): calcd for C24H26O6P [M + H]+, 441.1467; found, 441.1470.

(E)-Diethyl(2-(4-(4-bromophenyl)-2-oxo-6-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3i)

It (175 mg) was obtained from 1i (142 mg, 0.5 mmol) following general procedure A. It was obtained in 72% yield as a light yellow solid; mp 190–192 °C; R = 0.50 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.88 (dd, J = 7.5, 1.9 Hz, 2H), 7.66 (d, J = 8.3 Hz, 2H), 7.49 (d, J = 7.1 Hz, 3H), 7.25 (dt, J = 22.0, 8.0 Hz, 4H), 6.74 (s, 1H), 4.06 (p, J = 7.2 Hz, 4H), 1.30 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.1, 159.5, 156.0, 139.4 (d, J = 8.5 Hz), 135.3, 132.3, 131.6, 130.6, 130.0, 129.1, 125.9, 124.5, 120.5 (d, J = 185.0 Hz), 115.6 (d, J = 22.9 Hz), 104.6, 61.8 (d, J = 5.4 Hz), 16.3 (d, J = 6.4 Hz); 31P NMR (162 MHz, CDCl3): δ 19.2; IR (KBr): ν 3061, 2981, 1711, 1494, 1250, 1026, 965, 765 cm–1; HRMS(ESI): calcd for C23H23BrO5P [M + H]+, 489.0466; found, 489.0466.

(E)-Diethyl(2-(4-(4-fluorophenyl)-2-oxo-6-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3j)

It (139 mg) was obtained from 1j (112 mg, 0.5 mmol) following general procedure A. It was obtained in 65% yield as a light yellow solid; mp 150–152 °C; R = 0.50 (SiO2, 80% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.82 (dd, J = 7.5, 1.9 Hz, 2H), 7.45–7.39 (m, 3H), 7.31 (dd, J = 8.6, 5.2 Hz, 2H), 7.22–7.14 (m, 4H), 6.68 (s, 1H), 3.99 (p, J = 7.2 Hz, 4H), 1.22 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 163.5(d, JF–C = 251.6 Hz), 160.2, 159.3, 156.2, 139.5 (d, JP–C = 8.6 Hz), 132.5, 132.4, 131.5, 130.6 (d, JF–C = 8.4 Hz), 129.1, 125.9, 120.3 (d, JP–C = 185.1 Hz), 116.2 (d, JF–C = 22.0 Hz), 115.7 (d, JP–C = 22.6 Hz), 104.9, 61.8 (d, JP–C = 5.8 Hz), 16.3 (d, JP–C = 6.2 Hz); 31P NMR (162 MHz, CDCl3): δ 19.3; IR (KBr): ν 3065, 2983, 1708, 1499, 1243, 1025, 964, 767 cm–1; HRMS(ESI): calcd for C23H23FO5P [M + H]+, 429.1267; found, 429.1271.

(E)-Diethyl(2-(4-(3-chlorophenyl)-2-oxo-6-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3k)

It (150 mg) was obtained from 1k (120 mg, 0.5 mmol) following general procedure A. It was obtained in 68% yield as a light yellow solid; mp 169–171 °C; R = 0.52 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.83 (dd, J = 7.7, 1.9 Hz, 2H), 7.45–7.36 (m, 5H), 7.31 (s, 1H), 7.21–7.19 (m, 2H), 7.12 (dd, J = 22.0, 4.7 Hz, 1H), 6.67 (s, 1H), 4.00 (p, J = 7.2 Hz, 4H), 1.22 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.0, 159.6, 155.6, 139.1, 139.0, 138.2, 135.1, 131.6, 130.5, 130.3, 130.0, 129.1, 128.3, 126.7, 126.0, 121.7, 119.8, 116.0, 115.8, 104.5, 61.9, 61.8, 16.3, 16.3; 31P NMR (162 MHz, CDCl3): δ 19.1; IR (KBr): ν 3066, 2924, 1713, 1495, 1231, 1042, 943, 765 cm–1; HRMS(ESI): calcd for C23H23ClO5P [M + H]+, 445.0971; found, 445.0972.

(E)-Diethyl(2-(4-(6-methoxynaphthalen-2-yl)-2-oxo-6-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3l)

It (164 mg) was obtained from 1l (143 mg, 0.5 mmol) following general procedure A. It was obtained in 67% yield as a light yellow solid; mp 154–156 °C; R = 0.54 (SiO2, 80% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.95–7.89 (m, 2H), 7.86 (d, J = 8.4 Hz, 1H), 7.79 (d, J = 9.8 Hz, 2H), 7.53–7.46 (m, 3H), 7.43 (d, J = 8.4 Hz, 1H), 7.36–7.26 (m, 2H), 7.25–7.17 (m, 2H), 6.89 (s, 1H), 4.03 (p, 4H), 3.96 (s, 3H), 1.24 (t, J = 7.0 Hz, 6H); 31P NMR (162 MHz, CDCl3): δ 19.6; IR (KBr): ν 3062, 2984, 1711, 1492, 1238, 1024, 945, 777 cm–1 HRMS(ESI): calcd for C28H28O6P [M + H]+, 491.1623; found, 491.1624.

(E)-Diethyl(2-(2-oxo-6-phenyl-4-(pyridin-2-yl)-2H-pyran-3-yl)vinyl)phosphonate (3m)

It (129 mg) was obtained from 1m (103 mg, 0.5 mmol) following general procedure A. It was obtained in 63% yield as brown gum; mp 141–143 °C; R = 0.48 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 8.80 (d, J = 3.3 Hz, 1H), 7.89 (d, J = 18.3 Hz, 3H), 7.52–7.37 (m, 7H), 7.03 (s, 1H), 4.07 (P, 4H), 1.30 (t, J = 6.9 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.5, 159.6, 154.8, 154.1, 150.4, 139.5 (d, J = 8.44 Hz), 136.8, 131.4, 130.8, 129.0, 126.0, 125.1, 124.4, 120.9 (d, J = 184.1 Hz), 116.0 (d, J = 23.1 Hz), 104.2, 61.8 (d, J = 5.3 Hz), 16.3 (d, J = 6.3 Hz); 31P NMR (162 MHz, CDCl3): δ 19.3; IR (neat): ν 2924, 1719, 1458, 1274, 1027, 717 cm–1; HRMS(ESI): calcd for C22H23NO5P [M + H]+, 412.1313; found, 412.1313.

(E)-Diethyl(2-(2-oxo-4-phenyl-6-(p-tolyl)-2H-pyran-3-yl)vinyl)phosphonate (3p)

It (163 mg) was obtained from 1p (110 mg, 0.5 mmol) following general procedure A. It was obtained in 77% yield as a light yellow solid; mp 136–138 °C; R = 0.54 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.78 (d, J = 7.9 Hz, 2H), 7.49 (d, J = 5.6 Hz, 3H), 7.36 (d, J = 6.0 Hz, 2H), 7.25 (t, J = 14.5 Hz, 4H), 6.73 (s, 1H), 4.03 (p, 4H), 2.40 (s, 3H), 1.26 (t, J = 7.0 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.5, 159.5, 157.6, 142.2, 139.9 (d, J = 8.5 Hz), 136.7, 129.8, 129.8, 128.9, 128.4, 128.0, 125.9, 119.5 (d, J = 185.6 Hz), 115.1 (d, J = 22.7 Hz), 104.4, 61.7 (d, J = 5.3 Hz), 21.5, 16.3 (d, J = 6.3 Hz); 31P NMR (162 MHz, CDCl3): δ 19.7; IR (KBr): ν 3066, 2983, 1711, 1494, 1242, 1043, 948, 765 cm–1; HRMS(ESI): calcd for C24H26O5P [M + H]+, 425.1517; found, 425.1516.

(E)-Diethyl(2-(6-(4-fluorophenyl)-2-oxo-4-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3q)

It (139 mg) was obtained from 1q (112 mg, 0.5 mmol) following general procedure A. It was obtained in 65% yield as a light yellow solid; mp 156–158 °C; R = 0.50 (SiO2, 80% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.92–7.86 (m, 2H), 7.50 (dd, J = 5.8, 4.5 Hz, 3H), 7.39–7.34 (m, 2H), 7.26 (d, J = 2.4 Hz, 1H), 7.21 (d, J = 1.0 Hz, 1H), 7.16 (t, J = 8.6 Hz, 2H), 6.71 (s, 1H), 4.04 (p, J = 7.2 Hz, 4H), 1.27 (t, J = 7.1 Hz, 6H); 13C NMR (100 MHz, CDCl3): δ 164.6 (d, JF–C = 254.8 Hz), 160.2, 158.2, 157.4, 139.6 (d, JP–C = 8.9 Hz), 136.5, 130.0, 129.0, 128.4, 128.1 (d, JF–C = 8.7 Hz), 127.0, 120.1 (d, JP–C = 185.3 Hz), 116.4 (d, JF–C = 22.1 Hz), 115.5 (d, JP–C = 22.1 Hz) 104.8, 61.7 (d, JP–C = 5.4 Hz), 16.3 (d, JP–C = 6.3 Hz).31P NMR (162 MHz, CDCl3): δ 19.4; IR (KBr): ν 3064, 2983, 1717, 1496, 1249, 1029, 959, 779 cm–1; HRMS(ESI): calcd for C23H23FO5P [M + H]+, 429.1267; found, 429.1263.

(E)-Diethyl(2-(6-(4-chlorophenyl)-2-oxo-4-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3r)

It (155 mg) was obtained from 1r (120 mg, 0.5 mmol) following general procedure A. It was obtained in 70% yield as a light yellow solid; mp 166–168 °C; R = 0.50 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.85–7.80 (m, 2H), 7.54–7.48 (m, 3H), 7.47–7.43 (m, 2H), 7.39–7.35 (m, 2H), 7.28 (d, J = 0.9 Hz, 1H), 7.22 (d, J = 2.5 Hz, 1H), 6.76 (s, 1H), 4.05 (p, J = 7.2 Hz, 4H), 1.28 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.1, 157.9, 157.2, 139.5 (d, J = 8.4 Hz), 137.7, 136.4, 130.0, 129.4, 129.2, 129.0, 128.4, 127.1, 120.3 (d, J = 185.2 Hz), 115.9 (d, J = 22.6 Hz), 105.2, 61.8 (d, J = 5.7 Hz), 16.3 (d, J = 6.5 Hz); 31P NMR (162 MHz, CDCl3): δ 19.3; IR (KBr): ν 3070, 2984, 1711, 1489, 1234, 1044, 943, 766 cm–1; HRMS(ESI): calcd for C23H23ClO5P [M + H]+, 445.0971; found, 445.0972.

(E)-Diethyl(2-(6-(3-chlorophenyl)-2-oxo-4-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3s)

It (153 mg) was obtained from 1s (120 mg, 0.5 mmol) following general procedure A. It was obtained in 69% yield as a light yellow solid; mp 174–176 °C; R = 0.50 (SiO2, 70% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.87 (t, J = 1.8 Hz, 1H), 7.76 (dt, J = 7.5, 1.5 Hz, 1H), 7.54–7.48 (m, 3H), 7.47–7.43 (m, 1H), 7.42 (d, J = 7.7 Hz, 1H), 7.39–7.35 (m, 2H), 7.28 (d, J = 1.8 Hz, 1H), 7.22 (d, J = 3.7 Hz, 1H), 6.77 (s, 1H), 4.05 (p, J = 7.2 Hz, 4H), 1.27 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.0, 157.4, 157.0, 139.4 (d, J = 8.6 Hz), 136.3, 135.3, 132.5, 131.3, 130.3, 130.0, 129.0, 128.4, 125.9, 123.9, 120.6 (d, J = 185.1 Hz), 116.3 (d, J = 22.7 Hz), 105.7, 61.8 (d, J = 5.5 Hz), 16.3 (d, J = 6.3 Hz); 31P NMR (162 MHz, CDCl3): δ 19.2; IR (KBr): ν 3069, 2979, 1715, 1488, 1244, 1030, 783, 698 cm–1; HRMS(ESI): calcd for C23H23ClO5P [M + H]+, 445.0971; found, 445.0978.

(E)-Diethyl(2-(6-(4-nitrophenyl)-2-oxo-4-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3t)

It (138 mg) was obtained from 1t (125 mg, 0.5 mmol) following general procedure A. It was obtained in 61% yield as a yellow solid; mp 138–140 °C; R = 0.48 (SiO2, 80% EtOAc/hexanes); 1H NMR (500 MHz, CDCl3): δ 8.33 (d, J = 8.9 Hz, 2H), 8.06 (d, J = 8.9 Hz, 2H), 7.56–7.50 (m, 3H), 7.40–7.36 (m, 2H), 7.27 (dd, J = 23.3, 11.0 Hz, 2H), 6.91 (s, 1H), 4.06 (p, J = 7.2 Hz, 4H), 1.28 (t, J = 7.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 159.5, 156.5, 156.0, 149.0, 139.1 (d, J = 8.7 Hz), 136.3, 135.9, 130.3, 129.1, 128.4, 126.6, 124.3, 121.8 (d, J = 185.3 Hz), 117.6 (d, J = 22.6 Hz), 107.5, 61.9 (d, J = 5.4 Hz), 16.3 (d, J = 6.3 Hz); 31P NMR (162 MHz, CDCl3): δ 18.7; IR (KBr): ν 3070, 2989, 1719, 1491, 1239, 1017, 965, 754 cm–1; HRMS(ESI): calcd for C23H23NO7P [M + H]+, 456.1212; found, 456.1202.

(E)-Diethyl(2-(6-(furan-2-yl)-2-oxo-4-phenyl-2H-pyran-3-yl)vinyl)phosphonate (3u)

It (132 mg) was obtained from 1u (98 mg, 0.5 mmol) following general procedure A. It was obtained in 66% yield as dark brown gum; mp 141–143 °C; R = 0.50 (SiO2, 70% EtOAc/hexanes); 1H NMR (500 MHz, CDCl3): δ 7.55–7.45 (m, 4H), 7.36 (d, J = 6.6 Hz, 2H), 7.25–7.10 (m, 3H), 6.69 (s, 1H), 6.58 (s, 1H), 4.03 (p, 4H), 1.26 (t, J = 7.0 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 159.6, 157.5, 151.0, 146.2, 145.6, 139.8 (d, J = 8.7 Hz), 136.3, 129.9, 128.9, 128.5, 119.5 (d, J = 185.5 Hz), 115.1 (d, J = 22.5 Hz), 113.3, 112.8, 103.4, 61.7 (d, J = 5.3 Hz), 16.3 (d, J = 6.4 Hz); 31P NMR (162 MHz, CDCl3): δ 19.6; IR (neat): ν 2980, 2925, 1726, 1499, 1243, 1025, 965, 766 cm–1; HRMS(ESI): calcd for C21H22O6P [M + H]+, 401.1154; found, 401.1154.

(E)-Diethyl(2-(2-oxo-4-phenyl-6-(thiophen-2-yl)-2H-pyran-3-yl)vinyl)phosphonate (3v)

It (143 mg) was obtained from 1v (106 mg, 0.5 mmol) following general procedure A. It was obtained in 69% yield as a brown yellow solid; mp 109–111 °C; R = 0.52 (SiO2, 70% EtOAc/hexanes); 1H NMR (300 MHz, CDCl3): δ 7.69 (d, J = 3.2 Hz, 1H), 7.50 (d, J = 3.7 Hz, 5H), 7.36 (d, J = 4.9 Hz, 2H), 7.15 (dd, J = 9.1, 4.6 Hz, 2H), 6.60 (s, 1H), 4.04 (p, 4H), 1.27 (t, J = 7.0 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3): δ 159.7, 157.5, 154.9, 139.8 (d, J = 8.6 Hz), 136.4, 134.6, 130.1, 129.9, 129.0, 128.6, 128.4, 128.4, 119.5 (d, J = 185.3 Hz), 115.0 (d, J = 22.5 Hz), 104.1, 61.7 (d, J = 5.4 Hz), 16.3 (d, J = 6.3 Hz); 31P NMR (162 MHz, CDCl3): δ 19.6; IR (KBr): ν 3069, 2923, 1715, 1488, 1219, 1032, 940, 762 cm–1; HRMS(ESI): calcd for C21H22O5PS [M + H]+, 417.0925; found, 417.0935.

(E)-4,6-Diphenyl-3-(2-(phenylsulfonyl)vinyl)-2H-pyran-2-one (5a)

It (138 mg) was obtained from 1a (103 mg, 0.5 mmol) following general procedure A. It was obtained in 67% yield as a light yellow solid; mp 200–202 °C; R = 0.50 (SiO2, 60% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.90–7.84 (m, 5H), 7.59–7.54 (m, 5H), 7.52–7.47 (m, 5H), 7.39 (dd, J = 6.5, 2.9 Hz, 2H), 6.84 (s, 1H); 13C{1H} NMR (125 MHz, CDCl3): δ 160.2, 160.0, 159.5, 140.8, 136.0, 133.8, 133.2, 131.8, 131.7, 130.5, 130.5, 129.3, 129.2, 129.1, 128.5, 127.6, 126.1, 113.7, 105.1; IR (KBr): ν 3090, 2925, 1727, 1494, 1301, 1087, 770, 687 cm–1; HRMS(ESI): calcd for C25H19O4S [M + H]+, 415.1004; found, 415.0998.

(E)-4,6-Diphenyl-3-(2-tosylvinyl)-2H-pyran-2-one (5b)

It (150 mg) was obtained from 1a (103 mg, 0.5 mmol) following general procedure A. It was obtained in 70% yield as a light yellow solid; mp 140–142 °C; R = 0.50 (SiO2, 60% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.92–7.82 (m, 3H), 7.74 (d, J = 8.3 Hz, 2H), 7.59–7.54 (m, 3H), 7.48 (dt, J = 15.1, 8.4 Hz, 4H), 7.39 (dd, J = 6.5, 3.0 Hz, 2H), 7.31 (d, J = 8.1 Hz, 2H), 6.83 (s, 1H), 2.43 (s, 1H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.1, 160.0, 159.3, 144.2, 137.8, 136.0, 133.2, 132.1, 131.8, 130.5, 130.4, 129.8, 129.2, 129.1, 128.5, 127.7, 126.1, 105.1, 21.6; IR (KBr): ν 3060, 2924, 1728, 1508, 1299, 1084, 768, 663 cm–1; HRMS(ESI): calcd for C26H21O4S [M + H]+, 429.1160; found, 429.1160.

(E)-3-(Benzylideneamino)-4,6-diphenyl-2H-pyran-2-one (7a)

It (117 mg) was obtained from 1a (103 mg, 0.5 mmol) following general procedure A. It was obtained in 67% yield as a light yellow solid; mp 190–192 °C; R = 0.52 (SiO2, 10% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 9.42 (s, 1H), 7.90 (dd, J = 7.8, 1.9 Hz, 2H), 7.79 (dd, J = 7.8, 1.7 Hz, 2H), 7.64–7.60 (m, 2H), 7.49–7.45 (m, 6H), 7.45–7.39 (m, 3H), 6.97 (s, 1H); 13C{1H} NMR (100 MHz, CDCl3): δ 163.5, 159.3, 155.6, 146.1, 137.1, 136.2, 131.4, 131.3, 130.5, 130.0, 129.2, 129.1, 129.0, 128.6, 128.1, 127.9, 125.4, 104.9; IR (KBr): ν 3041, 2924, 1701, 1620, 1486, 1052, 758, 695 cm–1; HRMS(ESI): calcd for C24H18NO2 [M + H]+, 352.1337; found, 352.1338.

(E)-3-((4-Fluorobenzylidene)amino)-4,6-diphenyl-2H-pyran-2-one (7b)

It (114 mg) was obtained from 1a (103 mg, 0.5 mmol) following general procedure A. It was obtained in 62% yield as a light yellow solid; mp 169–171 °C; R = 0.48 (SiO2, 10% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 9.41 (s, 1H), 7.95–7.86 (m, 2H), 7.78 (dd, J = 8.3, 5.7 Hz, 2H), 7.60 (d, J = 3.5 Hz, 2H), 7.53–7.44 (m, 6H), 7.10 (t, J = 8.5 Hz, 2H), 6.96 (s, 1H); 13C{1H} NMR (100 MHz, CDCl3): δ 160.2, 159.9, 159.5, 136.4 (d, JF–C = 249.8 Hz), 136.0, 133.9, 132.3, 131.8, 130.5, 129.5 (d, JF–C = 13.1 Hz), 129.2, 129.1, 129.0, 128.5, 127.7 (d, JF–C = 39.1 Hz), 126.1, 122.6, 113.8, 105.1; IR (KBr): ν 3061, 2923, 1703, 1494, 1222, 1023, 761, 689 cm–1; HRMS(ESI): calcd for C24H17FNO2 [M + H]+, 370.1243; found, 370.1235.

(E)-4,6-Diphenyl-3-((1-phenylethylidene)amino)-2H-pyran-2-one (7c)

It (127 mg) was obtained from 1a (103 mg, 0.5 mmol) following general procedure A. It was obtained in 70% yield as a light yellow solid; mp 144–146 °C; R = 0.56 (SiO2, 20% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.90–7.87 (m, 4H), 7.52 (dd, J = 8.1, 1.4 Hz, 2H), 7.47–7.43 (m, 4H), 7.42–7.38 (m, 5H), 6.90 (s, 1H), 2.24 (s, 3H); 13C{1H} NMR (100 MHz, CDCl3): δ 170.3, 158.0, 154.3, 138.5, 137.7, 136.1, 131.6, 131.4, 130.9, 130.0, 129.0, 128.9, 128.6, 128.4, 128.3, 127.5, 125.0, 104.1, 19.8; IR (KBr): ν 3057, 2923, 1700, 1626, 1490, 1206, 938, 767 cm–1; HRMS(ESI): calcd for C25H20NO2 [M + H]+, 366.1494; found, 366.1493.

(E)-6-Phenyl-3-((1-phenylethylidene)amino)-4-(p-tolyl)-2H-pyran-2-one (7d)

It (136 mg) was obtained from 1b (110 mg, 0.5 mmol) following general procedure A. It was obtained in 72% yield as a light yellow solid; mp 172–174 °C; R = 0.56 (SiO2, 20% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.89 (dd, J = 14.1, 7.0 Hz, 4H), 7.48–7.38 (m, 8H), 7.19 (d, J = 8.0 Hz, 2H), 6.90 (s, 1H), 2.36 (s, 3H), 2.24 (s, 3H); 13C{1H} NMR (100 MHz, CDCl3): δ 170.2, 158.0, 154.2, 139.1, 138.6, 137.7, 133.1, 131.7, 131.1, 130.8, 129.9, 129.1, 128.9, 128.5, 128.3, 127.6, 125.0, 104.1, 21.3, 19.7; IR (KBr): ν 3060, 2918, 1692, 1497, 1207, 1057, 759, 687 cm–1; HRMS(ESI): calcd for C26H22NO2 [M + H]+, 380.1650; found, 380.1652.

(E)-4-(4-Bromophenyl)-6-phenyl-3-((1-phenylethylidene)amino)-2H-pyran-2-one (7e)

It (150 mg) was obtained from 1i (142 mg, 0.5 mmol) following general procedure A. It was obtained in 68% yield as a light yellow solid; mp 146–148 °C; R = 0.52 (SiO2, 20% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.92–7.85 (m, 4H), 7.54–7.50 (m, 2H), 7.48–7.39 (m, 8H), 6.84 (s, 1H), 2.25 (s, 3H); 13C{1H} NMR (100 MHz, CDCl3): δ 171.1, 170.59, 157.7, 154.5, 138.3, 136.4, 134.9, 131.6, 131.4, 131.1, 130.2, 130.1, 128.9, 128.4, 127.5, 125.0, 123.3, 103.5, 19.8; IR (KBr): ν 3054, 2915, 1708, 1485, 1204, 1065, 764, 688 cm–1; HRMS(ESI): calcd for C25H19BrNO2 [M + H]+, 444.0599; found, 444.0603.

(E)-4-Phenyl-3-((1-phenylethylidene)amino)-6-(thiophen-2-yl)-2H-pyran-2-one (7f)

It (126 mg) was obtained from 1v (106 mg, 0.5 mmol) following general procedure A. It was obtained in 68% yield as a light yellow solid; mp 144–146 °C; R = 0.56 (SiO2, 20% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 7.88 (d, J = 7.2 Hz, 2H), 7.59 (d, J = 2.9 Hz, 1H), 7.50 (d, J = 6.9 Hz, 2H), 7.46–7.32 (m, 7H), 7.12 (t, 1H), 6.72 (s, 1H), 2.24 (s, 3H); 13C{1H} NMR (100 MHz, CDCl3): δ 170.4, 157.3, 150.3, 138.5, 137.9, 135.8, 135.4, 130.98, 130.9, 129.3, 129.0, 128.6, 128.4, 128.3, 127.8, 127.5, 126.1, 103.4, 19.8; IR (KBr): ν 3062, 2922, 1707, 1423, 1200, 1053, 922, 762 cm–1; HRMS(ESI): calcd for C23H18NO2S [M + H]+, 372.1058; found, 372.1056.

(E)-3-((4-Bromobenzylidene)amino)-4,6-diphenyl-2H-pyran-2-one (7g)

It (145 mg) was obtained from 1a (103 mg, 0.5 mmol) following general procedure A. It was obtained in 68% yield as a light yellow solid; mp 178–180 °C; R = 0.52 (SiO2, 10% EtOAc/hexanes); 1H NMR (400 MHz, CDCl3): δ 9.43 (s, 1H), 7.91–7.89 (m, 2H), 7.64 (d, J = 8.5 Hz, 2H), 7.60–7.58 (m, 2H), 7.54 (d, J = 8.5 Hz, 2H), 7.59–7.46 (m, 6H), 6.97 (s, 1H); 13C{1H} NMR (100 MHz, CDCl3): δ 161.8, 159.2, 155.9, 147.0, 136.2, 136.1, 131.9, 131, 130.6, 130.4, 130.0, 129.3, 129.0, 127.9, 127.5, 125.9, 125.5, 105.0; IR (KBr): ν 3054, 2920, 1714, 1618, 1478, 1066, 756, 687 cm–1; HRMS(ESI): calcd for C24H17BrNO2 [M + H]+, 430.0442; found, 430.0433.