Tandem Double [3 + 2] Cycloaddition Reactions at Both C-1 and C-3 Atoms of N-Cyanomethylisoquinolinium Ylide.

The base-promoted cycloaddition reaction of N-cyanomethylisoquinolinium chloride with 2-arylidene-1,3-indanediones in dry tetrahydrofuran resulted in the expected spiro[indene-2,1'-pyrrolo[2,1-a]isoquinoline] derivatives. However, the triethylamine-promoted three-component reaction of N-cyanomethylisoquinolinium chloride, aromatic aldehydes, and two molecules of 1,3-indanediones in acetonitrile afforded unique spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2'-indene] derivatives in satisfactory yields through tandem double [3 + 2] cycloaddition reactions.

Introduction

As one of the reactive heteroaromatic N-ylides, isoquinolinium ylides have been attracting continuous attention due to their easy preparation and versatile reactivity and become one of the most valuable synthons for the construction of nitrogen-containing heterocyclic systems.[1,2] Isoquinolinium ylides can be conveniently generated in situ from deprotonation of the corresponding N-substituted methylisoquinolinium salts in basic media.[3] The most common reaction of isoquinolinium ylide is the [3 + 2] cycloaddition reaction with various 1,3-dipolarophiles to give pyrrolo[2,1-a]isoquinoline derivatives (eq 1 in Scheme ).[4] By employing various substrates and adopting different reaction conditions, these kinds of reactions have resulted in many pyrrolo[2,1-a]isoquinoline derivatives and related spiro or polycyclic systems with valuable molecular diversity and regulated diastereoselectivity.[5] In recent years, new synthetic reaction patterns of isoquinolinium ylides have been successfully revealed, which indicated that there are many unknown characters in the chemistry of isoquinolinium ylides.[6] For examples, the base-promoted reaction of N-phenacylisoquinolinium ylides with arylidene Meldrum acid resulted in stable zwitterionic salts.[7a] More notably, the isoquinolinium zwitterionic salts with an unusual C-4 substitution pattern were also obtained from the reaction of N-benzylisoquinolinium ylides with aromatic aldehydes and cyclic 1,3-dicarbonyl compounds (eq 2 in Scheme ).[7b] The base-mediated three-component reaction of N-alkoxycarbonylmethylisoquinolinium salts, aromatic aldehydes, and 1,3-indanedione afforded the unprecedented complex polycyclic compounds, in which the generated isoquinilonium ylide not only behaved as a reactive 1,3-dipole but also acted as a useful diene to accomplish sequential 1,3-dipolar cycloaddition and the Diels–Alder reaction (eq 3 in Scheme ).[8] In continuation of our aim to exploit the potential synthetic applications of the heteroaromatic N-ylides,[8] herein, we wish to reveal the unprecedented reactions of N-cyanomethylisoquinolinium chloride with 2-arylidene-1,3-indanediones under different reaction conditions. The reaction not only gave the normal spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline] derivatives through the normal 1,3-dipolar cycloaddition reaction but also afforded unique spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene] derivatives by the domino cyclization process (eq 4 in Scheme ).

Scheme 1

Illustration of Typical Reaction Patterns of Isoquinolinium Ylides

Results and Discussion

Initially, the conditions for the reaction of N-cyanomethylisoquinolinium chloride with 2-benzylidene-1,3-indanedione were briefly examined on the basis of our previously established reaction conditions for the N-phenacyl and N-ethoxycarbonylmethylisoquinolinium salts.[8] When the reaction was carried out in the solvent of MeOH, EtOH, CH3CN and dry tetrahydrofuran (THF) in the presence of triethylamine as base for about 10 h, the expected spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline], 1a, was obtained in 47, 51, 56, and 81% yields. When 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and piperidine were used as base, the reaction in dry THF gave 45, 59, and 57% yields. When the triethylamine-promoted reaction was carried out in THF at about 50 °C for 5 h, the yield of product 1a greatly decreased to 31%. Thus, in the presence of slight excess triethylamine, the reactions of N-cyanomethylisoquinolinium chloride with various 2-arylidene-1,3-indanediones in dry THF at room temperature (rt) for about 10 h afforded spiro[indene-2,1′-pyrrolo[2,1-a]isoquinolines] 1a–f in good yields. The structures of spiro compounds were successfully characterized by IR, high-resolution mass spectrometry (HRMS), 1H NMR, and 13C NMR spectra. It should be pointed out that spiro compounds 1a–f are not very stable in solution, especially in the protonic solvent or hydrous solvent. It must be quick to separate samples and record their 1H and 13C NMR spectra. The formation of spiro[indene-2,1′-pyrrolo[2,1-a]isoquinolines] 1a–f obviously took place from the normal [3 + 2] cycloaddition of the in situ-generated isoquinolinium ylide with 2-arylidene-1,3-indanediones. The 1H NMR and 13C NMR spectra clearly indicated that only one diastereoisomer exists in the obtained samples of the products. On the basis of NMR spectra and previously obtained results, we tentatively assigned the spiro compounds 1a–f having trans-configuration.

Because 2-arylidene-1,3-indanediones were initially prepared from the base-catalyzed condensation of aromatic aldehydes with 1,3-indanedione, it is natural to test the possibility of converting the above reaction to a one-pot three-component reaction. When equal amounts of N-cyanomethylisoquinolinium chloride, benzaldehyde, and 1,3-indanedione were stirred in ethanol in the presence of triethylamine, instead of the formation of above spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline], a unique spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene] 2a was obtained in 31% yield, in which two scaffolds of 1,3-indanedione were eventually included in the molecule. When excess 1,3-indanedione was employed and triethylamine was used as the base, the reaction in MeOH, EtOH, and CH3CN gave new product 2a in 51, 67, and 83% yields, respectively. When other bases such as DABCO, DBU, and Na2CO3 were used as the base, the yield of the product did not increase. Prolonging reaction time or carrying out the reaction at an elevated temperature also caused a decrease in yield. Thus, the best conditions for this reaction are carrying out the reaction in acetonitrile at room temperature in the presence of triethylamine as the base promoter. Under these convenient reaction conditions, the reaction scope was investigated, and the obtained results are summarized in Tables and 2. We were pleased to find that various aromatic aldehydes with different substituents reacted smoothly to give spiro polycyclic compounds 2a–o in high yields. Some heterocylic substituted aldehydes, such as 2-furfural, 2-thiophenecarbaldehyde, picolinaldehyde, nicotinaldehyde, and isonicotinaldehyde, also gave desired products 2p–t in good yields. n-Heptaldehyde was also successfully employed in the reaction to give spiro products 2x and 2y in good yields. Phenylglyoxal also afforded benzoyl-substituted product 2y in 85% yield. On the other hand, the reaction with substituted isoquinolines such as 5-bromoisoquinoline also resulted in spiro products 2v and 2w in satisfactory yields. These results indicated that this reaction has a wide variety of substrates.

Table 1

Synthesis of Spiro[indene-2,1′-pyrrolo[2,1-a]isoquinolines] 1a–fa

entry	compd	Ar	yield (%)b
1	1a	C6H5	81
2	1b	o-CH3OC6H4	84
3	1c	p-CH3C6H4	79
4	1d	p-BrC6H4	83
5	1e	p-ClC6H4	81
6	1f	p-(t-Bu)C6H4	61

Reaction conditions: isoquinolinium salt (0.5 mmol), 2-arylidene-1,3-indanedione (0.5 mmol), Et3N (0.6 mmol), THF (15.0 mL), rt, 10 h.

Isolated yields.

Table 2

Synthesis of Polycyclic Spiro Compounds 2a–ua

entry	compd	R	Ar	yield (%)b
1	2a	H	C6H5	83
2	2b	H	o-HOC6H4	78
3	2c	H	o-CH3OC6H4	87
4	2d	H	o-ClC6H4	89
5	2e	H	o-BrC6H4	85
6	2f	H	m-CH3C6H4	86
7	2g	H	m-FC6H4	81
8	2h	H	m-NO2C6H4	82
9	2i	H	p-CH3C6H4	92
10	2j	H	p-(CH3)2NC6H4	73
11	2k	H	p-BrC6H4	87
12	2l	H	p-ClC6H4	91
13	2m	H	p-t-C(CH3)3C6H4	81
14	2n	H	p-NO2C6H4	79
15	2o	H	2-HO-4-ClC6H3	72
16	2p	H	2-furan	69
17	2q	H	2-thiophen	78
18	2r	H	2-Py	83
19	2s	H	3-Py	76
20	2t	H	4-Py	74
21	2u	H	benzoyl	85
22	2v	Br	p-ClC6H4	81
23	2w	Br	p-NO2C6H4	83
24	2x	H	n-Hex	70
25	2y	Br	n-Hex	63

Reaction conditions: isoquinolinium salt (0.5 mmol), aldehyde (0.5 mmol), 1,3-indanedione (1.1 mmol), Et3N (1.2 mmol), CH3CN (15.0 mL), rt, 8 h.

Isolated yields.

The structures of spiro compounds 2a–y were successfully determined by various spectroscopy techniques. The single-crystal structures of two representative compounds 2i and 2l were successfully determined by the X-ray diffraction method (Figure ). From Figures and 2, it can be seen that both C-1 and C-3 atoms of isoquinolinium ylide took part in the reaction. Although the pyridinium salts sometimes undergo the double [3 + 2] cycloaddition reaction at both C-1 and C-6 atoms to give novel pyrrolo[2,1,5-cd]indolizine derivatives,[10] it is rare for isoquinolinium salts to undergo such double [3 + 2] cycloaddition reactions at both C-1 and C-3 atoms of the isoquinoline ring. The only example is the early report about the formation of benzocyclo[3.2.2]azines in lower yield from the double [3 + 2] cycloaddition reaction of isoquinolinium ylide with N-methylmaleimide.[11a] Another related example is the NHC-catalyzed enantioselective dearomatizing double Mannich reaction at both C-1 and C-3 atoms of isoquinolinium salts to give 8-azabicyclo[3.2.1]octane derivatives.[11b] On the other hand, there are several reports about the cyano group to take part in the sequential cyclization process in the reactions of N-cyanomethylpyridinium salts and N-cyanomethylisoquinolinium salts.[12] Here, the normal [3 + 2] cycloaddition at 1,2-positions of isoquinolinium ylide was replaced by the abnormal [3 + 2] cycloaddition at 2,3-positions of isoquinolinium ylide and internal cyclization at the C-1 position. This kind of reaction pattern might be observed for the first time in the reactions of isoquinolinium ylides. It is also noticed that this reaction successfully provided a convenient dearomatizing method for the isoquinoline ring.

Figure 1

Single-crystal structure of compounds 2i.

Figure 2

Single-crystal structure of compounds 2l.

Although the exact mechanism is not completely understood at the present time, a plausible reaction mechanism is proposed on the basis of the above results and the previously reported reactions (Scheme ).[9−12] First, an isoquinolinium ylide (A) was generated from deprotonation of N-cyanomethylisoquinolinium salt. In the meantime, 2-arylidene-1,3-indanedione was also formed from the Knoevenagel condensation of the respective aromatic aldehyde with 1,3-indanedione in the presence of triethylamine. Second, a Michael addition of a isoquinolinium ylide (A) to 2-arylidene-1,3-indanedione afforded a zwitterionic intermediate (B). Third, the intermolecular cyclization resulted in spiro compound 1 in dry THF. Spiro compound 1 is not very stable and is in equilibrium with the zwitterionic intermediate (B) in acetonitrile. Then, the nucleophilic addition of the carbanion of 1,3-indanedione to the cyano group generated an imine intermediate (C), which in turn added to the cyclic iminium ion to give a cyclic intermediate (D). Finally, the intermolecular nucleophilic addition of carbanion to enamine resulted in polycyclic product 2 with the corresponding protonation and proton immigration process. Here, the unique dual reactivities of the cyano group and 1,3-indanedione are the crucial factors for completing this reaction sequence.

Scheme 2

Proposed Reaction Mechanism

To probe the credibility of our proposed mechanistic scheme and shed more light on the formation of polycyclic spiro compounds, further control experiments were carried out (Scheme ). First, an equal combination of 1,3-indanedione and initially prepared 2-arylidene-1,3-indanedione was used in the three-component reaction, and corresponding spiro compounds 2a, 2f, and 2k were obtained in very high yields, which clearly indicated that 2-arylidene-1,3-indanedione was the intermediate in the reaction. Second, the reaction of initially prepared spiro[indene-2,1′-pyrrolo[2,1-a]isoquinolines] 1 with 1,3-indandione in acetonitrile in the presence of triethylamine for overnight resulted in polycyclic spiro compounds 2a and 2m in moderate yields, which clearly showed that spiro[indene-2,1′-pyrrolo[2,1-a]isoquinolines] 1 decomposed to the zwitterionic intermediate (B) in the solution, which is the key intermediate in the above proposed mechanism.

Scheme 3

Control Experiments

Conclusions

In summary, we have successfully investigated the base-promoted cycloaddition reaction of N-cyanomethylisoquinolinium chloride with 2-arylidene-1,3-indanediones under different reaction conditions. The reaction not only gave the normal spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline] derivatives through the normal 1,3-dipolar cycloaddition reaction but also afforded unique spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene] derivatives via tandem double [3 + 2] cycloaddition reactions. The reaction originated from the versatile reactivity of the well-known heteroaromatic N-ylides and successfully revealed a new reaction pattern for isoquinolinium ylides in heterocyclic synthesis. The potential applications of this convenient synthetic protocol in organic and medicinal chemistry might be significant.

Experimental Section

General Procedure for the Preparation of Spiro[indene-2,1′-pyrrolo[2,1-a]isoquinolines] 1a–f

A mixture of N-cyanomethylisoquinolinium chloride (0.5 mmol), 2-arylidene-1,3-indanedione (0.5 mmol), and triethylamine (0.6 mmol) in dry tetrahydrofuran (15.0 mL) was stirred at room temperature for 10 h. The solvent was removed at reduced pressure by rotatory evaporation. The residue was titrated with a mixture of light petroleum and methylene dichloride to give the pure solid.

1,3-Dioxo-2′-phenyl-1,2′,3,3′-tetrahydro-10b′H-spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline]-3′-carbonitrile (1a)

Yellow solid, 81%, mp 161–163 °C 1H NMR (400 MHz, DMSO-d6) δ: 7.78–7.76 (m, 4H, Ar H), 7.20–7.16 (m, 5H, Ar H), 6.94 (t, J = 7.2 Hz, 1H, Ar H), 6.85 (d, J = 7.6 Hz, 1H, Ar H), 6.59–6.35 (m, 2H, Ar H), 6.23 (d, J = 7.6 Hz, 1H, CH), 5.84 (s, 1H, CH), 5.68 (d, J = 10.0 Hz, 1H, CH), 5.36 (d, J = 7.6 Hz, 1H, CH), 4.29 (d, J = 10.0 Hz, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 198.1, 142.6, 137.0, 134.0, 132.5, 132.1, 129.3, 129.2, 129.0, 128.5, 125.7, 125.2, 125.1, 125.0, 123.2, 119.3, 100.3, 71.1, 71.0, 57.1, 53.9; IR (KBr) υ: 3061, 2924, 2860, 2238, 1810, 1696, 1592, 1491, 1420, 1244, 1033, 854, 760 cm–1; HRMS (ESI) calcd for C27H19N2O2([M + H]+): 403.1441, found: 403.1452.

2′-(2-Methoxyphenyl)-1,3-dioxo-1,2′,3,3′-tetrahydro-10b′H-spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline]-3′-carbonitrile (1b)

Yellow solid, 84%, mp 162–164 °C; 1H NMR (400 MHz, DMSO-d6) δ: 7.79–7.71 (m, 4H, Ar H), 7.41 (d, J = 7.2 Hz, 1H, Ar H), 7.15 (t, J = 7.6 Hz, 1H, Ar H), 6.98–6.91 (m, 3H, Ar H), 6.65 (d, J = 7.6 Hz, 1H, CH), 6.61–6.56 (m, 2H, Ar H), 6.19 (d, J = 7.6 Hz, 1H, Ar H), 5.66 (d, J = 7.6 Hz, 1H, CH), 5.47–5.45 (m 2H, CH), 4.23–4.22 (m, 1H, CH), 3.12 (s, 3H, OCH3); 13C NMR (100 MHz, DMSO-d6) δ: 198.1, 156.7, 142.2, 136.5, 132.6, 129.7, 128.9, 127.9, 125.6, 125.2, 124.9, 122.9, 120.8, 110.7, 69.8, 68.2, 56.0, 54.6, 49.4; IR (KBr) υ: 3031, 2928, 2269, 1738, 1704, 1593, 1548, 1540, 1359, 1262, 836, 813, 769, 675 cm–1; HRMS (ESI) calcd for C28H21N2O3([M + H]+): 433.1547, found: 433.1560.

1,3-Dioxo-2′-(p-tolyl)-1,2′,3,3′-tetrahydro-10b′H-spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline]-3′-carbonitrile (1c)

Yellow solid, 79%, mp 181–183 °C; 1H NMR (400 MHz, CDCl3) δ: 7.91–7.90 (m, 1H, Ar H), 7.73–7.69 (m, 1H, Ar H), 7.63–7.62 (m, 2H, Ar H), 7.06 (d, J = 8.0 Hz, 2H, Ar H), 6.97–6.92 (m, 3H, Ar H), 6.83 (d, J = 7.2 Hz, 1H, Ar H), 6.54 (d, J = 7.6 Hz, 1H, Ar H), 6.33 (d, J = 7.2 Hz, 1H, CH), 6.25 (d, J = 7.6 Hz, 1H, Ar H), 5.84 (s, 1H, CH), 5.39 (d, J = 7.2 Hz, 1H, CH), 5.16 (d, J = 10.4 Hz, 1H, CH), 4.29 (d, J = 10.8 Hz, 1H, CH), 2.18 (s, 3H, CH3); 13C NMR (100 MHz, DMSO-d6) δ: 198.2, 142.7, 138.4, 137.1, 134.1, 132.4, 129.7, 129.1, 128.9, 128.4, 125.6, 125.2, 125.1, 125.0, 123.2, 119.3, 100.1, 70.9, 69.4, 57.2, 53.7, 20.9; IR (KBr) υ: 3059, 2916, 2275, 1740, 1704, 1591, 1562, 1540, 1353, 878, 803, 772, 680 cm–1; HRMS (ESI) calcd for C28H21N2O2([M + H]+): 417.1598, found: 417.1611.

2′-(4-Bromophenyl)-1,3-dioxo-1,2′,3,3′-tetrahydro-10b′H-spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline]-3′-carbonitrile (1d)

Yellow solid, 83%, mp 177–179 °C; 1H NMR (400 MHz, DMSO-d6) δ: 7.78–7.75 (m, 4H, Ar H), 7.41 (d, J = 8.0 Hz, 2H, Ar H), 7.16 (d, J = 8.0 Hz, 2H, Ar H), 6.98 (d, J = 7.2 Hz, 1H, Ar H), 76.89 (d, J = 7.6 Hz, 1H, Ar H), 6.64–6.60 (m, 2H, Ar H), 6.29 (d, J = 7.6 Hz, 1H, CH), 5.91 (s, 1H, CH), 5.73 (d, J = 10.0 Hz, 1H, CH), 5.44 (d, J = 7.6 Hz, 1H, CH), 4.31 (d, J = 10.4 Hz, 1H, CH),; 13C NMR (100 MHz, DMSO-d6) δ: 197.7, 142.5, 137.0, 133.9, 132.5, 132.1, 131.9, 130.8, 129.5, 125.9, 125.3, 125.3, 125.0, 123.1, 122.3, 119.0, 101.0, 71.7, 71.7, 57.2, 52.9; IR (KBr) υ: 3060, 2911, 2231, 1736, 1702, 1593, 1489, 1418, 1248, 766, 718 cm–1; HRMS (ESI) calcd for C27H18BrN2O2([M + H]+): 781.0546, found: 481.0542.

2′-(4-Chlorophenyl)-1,3-dioxo-1,2′,3,3′-tetrahydro-10b′H-spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline]-3′-carbonitrile (1e)

Yellow solid, 81%, mp 180–183 °C; 1H NMR (600 MHz, CDCl3) δ: 7.91–7.90 (m, 1H, Ar H), 7.74–7.73 (m, 1H, Ar H), 7.67–7.62 (m, 2H, Ar H), 7.17–7.13 (m, 4H, Ar H), 6.93 (t, J = 7.2 Hz, 1H, Ar H), 6.84 (d, J = 7.2 Hz, 1H, Ar H), 6.54 (d, J = 7.2 Hz, 1H, Ar H), 6.32 (d, J = 6.6 Hz, 1H, CH), 6.24 (d, J = 7.8 Hz, 1H, Ar H), 5.81 (s, 1H, CH), 5.41 (d, J = 6.0 Hz, 1H, CH), 5.14 (d, J = 10.2 Hz, 1H, CH), 4.28 (d, J = 10.2 Hz, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.1, 142.9, 136.0, 136.0, 134.8, 132.3, 131.8, 129.7, 129.6, 129.1, 128.7, 125.4, 125.3, 124.8, 124.8, 123.1, 109.9, 101.1, 70.1, 68.6, 57.7, 53.6; IR (KBr) υ: 3064, 2914, 2240, 1739, 1704, 1590, 1489, 1456, 1276, 1095, 849, 737 cm–1; HRMS (ESI) calcd for C27H18ClN2O2([M + H]+): 437.1051, found: 437.1045.

2′-(4-(tert-Butyl)phenyl)-1,3-dioxo-1,2′,3,3′-tetrahydro-10b′H-spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline]-3′-carbonitrile (1f)

Yellow solid, 61%, mp 176–178 °C; 1H NMR (400 MHz, CDCl3) δ: 7.91–7.90 (m, 1H, Ar H), 7.72–7.69 (m, 1H, Ar H), 7.63–7.62 (m, 2H, Ar H), 7.16 (d, J = 8.4 Hz, 2H, Ar H), 7.09 (d, J = 8.4 Hz, 2H, Ar H), 6.93 (t, J = 7.6 Hz, 1H, Ar H), 6.83 (d, J = 7.2 Hz, 1H, Ar H), 6.54 (t, J = 7.6 Hz, 1H, Ar H), 6.33 (d, J = 7.2 Hz, 1H, CH), 6.25 (d, J = 7.6 Hz, 1H, Ar H), 5.83 (s, 1H, CH), 5.39 (d, J = 6.8 Hz, 1H, CH), 5.16 (d, J = 10.4 Hz, 1H, CH), 4.30 (d, J = 10.8 Hz, 1H, CH), 1.16 (s, 9H, 3CH3); 13C NMR (100 MHz, DMSO-d6) δ: 198.1, 151.4, 142.7, 137.0, 134.2, 132.4, 129.2, 129.1, 128.3, 126.0, 125.6, 125.2, 125.1, 125.0, 123.2, 119.4, 100.2, 100.1, 71.1, 70.0, 57.4, 53.4, 34.6, 31.2; IR (KBr) υ: 3057, 2961, 2867, 2257, 1739, 1700, 1595, 1500, 1267, 1084, 951, 805, 762, 721 cm–1; HRMS (ESI) calcd for C31H27N2O2([M + H]+): 459.2067, found: 459.2081.

General Procedure for the Preparation of Spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indenes] 2a–y

A mixture of N-cyanomethylisoquinolinium chloride (0.5 mmol), aromatic aldehyde (0.5 mmol), 1,3-indanedione (1.1 mmol), and triethylamine (1.2 mmol) in acetonitrile (15.0 mL) was stirred at room temperature for 8 h. The resulting precipitates were collected by filtration and washed with cold ethanol to give pure products 2a–v for analysis. In the cases of reactions with n-heptanal, the crude products were subjected to column chromatography with a mixture of light petroleum and ethyl acetate (v/v = 2:1) as an eluent to give pure products 2x and 2y for analysis.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-phenyl-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2a)

White solid, 83%, mp 249–251 °C; 1H NMR (400 MHz, CDCl3) δ: 10.29 (s, 1H, NH), 7.39 (d, J = 7.6 Hz, 1H, Ar H), 7.76 (t, J = 7.6 Hz, 1H, Ar H), 7.72–7.65 (m, 3H, Ar H), 7.61 (d, J = 6.8 Hz, 1H, Ar H), 7.57–7.51 (m, 2H, Ar H), 7.44 (d, J = 7.2 Hz, 1H, Ar H), 7.33 (t, J = 7.6 Hz, 1H, Ar H), 7.27 (t, J = 7.6 Hz, 1H, Ar H), 7.19–7.11 (m, 5H, Ar H), 7.01 (d, J = 7.2 Hz, 1H, Ar H), 5.99 (s, 1H, CH), 5.44 (d, J = 6.8 Hz, 1H, CH), 4.66–4.65 (m, 1H, CH), 3.54 (d, J = 10.4 Hz, 1H, CH), 2.93 (t, J = 12.4 Hz, 1H, CH), 2.41–2.36 (m, 1H, CH); 13C NMR (100 MHz, CDCl3) δ: 199.7, 197.5, 194.0, 188.7, 165.7, 142.9, 141.5, 139.9, 139.7, 137.6, 136.1, 135.5, 134.8, 133.2, 132.8, 129.7, 129.1, 129.0, 128.0, 127.9, 127.3, 127.1, 123.1, 123.0, 122.0, 121.2, 100.9, 77.3, 74.5, 67.8, 62.4, 56.3, 30.1; IR (KBr) υ: 3276, 3026, 2916, 1738, 1703, 1570, 1457, 1273, 1087, 859, 739 cm–1; HRMS (ESI) calcd for C36H25N2O4([M + H]+): 549.1809, found: 549.1818.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(2-hydroxyphenyl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2b)

White solid, 78%, mp 247–249 °C; 1H NMR (400 MHz, CDCl3) δ: 10.43 (s, 1H, NH), 9.00 (s, 1H, OH), 7.91–7.88 (m, 3H, Ar H), 7.83–7.80 (m, 1H, Ar H), 7.66–7.60 (m, 4H, Ar H), 7.50–7.45 (m, 2H, Ar H), 7.34 (t, J = 7.6 Hz, 1H, Ar H), 7.29–7.26 (m, 1H, Ar H), 7.08 (d, J = 7.6 Hz, 1H, Ar H), 6.90–6.86 (m, 1H, Ar H), 6.74 (t, J = 7.2 Hz, 1H, Ar H), 6.38 (d, J = 8.0 Hz, 1H, Ar H), 5.95 (s, 1H, CH), 5.51–5.50 (m, 1H, CH), 4.64 (d, J = 3.6 Hz, 1H, CH), 3.21 (dd, J1 = 11.6 Hz, J2 = 2.4 Hz, 1H, CH), 2.62–2.55 (m, 1H, CH), 2.35 (dd, J1 = 15.2 Hz, J2 = 2.4 Hz, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.7, 197.4, 191.9, 188.2, 167.3, 154.3, 142.3, 141.4, 139.7, 139.5, 136.4, 136.2, 135.4, 133.8, 133.6, 130.4, 129.7, 129.3, 129.1, 128.5, 127.5, 127.2, 125.8, 123.2, 122.9, 121.6, 121.2, 118.7, 114.4, 100.0, 77.7, 73.7, 65.9, 63.4, 48.7, 29.9; IR (KBr) υ: 3265, 3069, 2910, 1745, 1707, 1566, 1457, 1206, 1139, 997, 862, 741, 694, 655 cm–1; HRMS (ESI) calcd for C36H25N2O5([M + H]+): 565.1758, found: 565.1757.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(2-methoxyphenyl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2c)

White solid, 87%, mp 266–268 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.45 (s, 1H, NH), 8.02 (d, J = 7.2 Hz, 1H, Ar H), 7.94–7.92 (m, 2H, Ar H), 7.85 (t, J = 7.2 Hz, 1H, Ar H), 7.68–7.60 (m, 5H, Ar H), 7.52 (d, J = 6.8 Hz, 1H, Ar H), 7.37 (t, J = 7.6 Hz, 1H, Ar H), 7.31 (t, J = 7.6 Hz, 1H, Ar H), 7.12–7.10 (m, 2H, Ar H), 6.97 (t, J = 7.6 Hz, 1H, Ar H), 6.58 (d, J = 8.0 Hz, 1H, Ar H), 6.00 (s, 1H, CH), 5.63 (s, 1H, CH), 4.67–4.66 (m, 1H, CH), 3.30–3.28 (m, 1H, CH), 2.95 (s, 3H, CH3), 2.64 (t, J = 7.2 Hz, 1H, CH), 2.43 (d, J = 10.8 Hz, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.4, 197.2, 191.9, 188.4, 167.1, 155.5, 142.1, 141.1, 139.7, 139.5, 136.5, 136.3, 135.4, 133.8, 133.7, 130.4, 129.7, 129.3, 129.1, 128.1, 128.0, 127.4, 127.2, 123.1, 122.9, 121.6, 121.2, 120.5, 110.2, 100.0, 77.8, 73.0, 65.6, 63.1, 54.3, 49.1, 29.8; IR (KBr) υ: 3252, 3072, 2833, 1746, 1708, 1649, 1567, 1492, 1462, 1360, 1275, 1206, 1029, 933, 853, 697 cm–1; HRMS (ESI) calcd for C37H27N2O5([M + H]+): 579.1914, found: 579.1920.

3-(2-Chlorophenyl)-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2d)

White solid, 89%, mp 264–266 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.46 (s, 1H, NH), 7.98–7.92 (m, 3H, Ar H), 7.88 (t, J = 7.2 Hz, 1H, Ar H), 7.74 (d, J = 7.6 Hz, 1H, Ar H), 7.70–7.65 (m, 4H, Ar H), 7.56–7.55 (m, 1H, Ar H), 7.38–7.32 (m, 3H, Ar H), 7.17–7.12 (m, 3H, Ar H), 6.02 (s, 1H, CH), 5.46 (s, 1H, CH), 4.84–4.83 (m, 1H, CH), 3.37–3.34 (m, 1H, CH), 2.74 (t, J = 12.4 Hz, 1H, CH), 2.52–2.51 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.9, 196.9, 191.6, 188.5, 166.0, 141.9, 141.8, 139.7, 139.5, 137.3, 136.8, 136.7, 135.3, 133.9, 133.7, 133.4, 131.0, 130.3, 129.9, 129.3, 129.2, 129.0, 128.7, 127.2, 127.0, 123.6, 123.1, 121.6, 121.3, 99.9, 78.0, 76.1, 65.8, 63.4, 52.1, 29.7; IR (KBr) υ: 3279, 3069, 2907, 2836, 1746, 1709, 1659, 1572, 1461, 1436, 1205, 1036, 891, 850, 792, 685 cm–1; HRMS (ESI) calcd for C36H24ClN2O4([M + H]+): 583.1419, found: 583.1421.

3-(2-Bromophenyl)-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2e)

White solid, 85%, mp 270–272 °C; 1H NMR (600 MHz, CDCl3) δ: 10.21 (s, 1H, NH), 8.42–8.37 (m, 2H, Ar H), 7.97 (d, J = 7.2 Hz, 1H, Ar H), 7.83–7.73 (m, 5H, Ar H), 7.63–7.55 (m, 3H, Ar H), 7.46 (d, J = 7.8 Hz, 1H, Ar H), 7.36 (t, J = 7.8 Hz, 1H, Ar H), 7.30 (t, J = 7.2 Hz, 1H, Ar H), 7.26–7.24 (m, 1H, Ar H), 7.03 (d, J = 7.2 Hz, 1H, Ar H), 6.00 (s, 1H, CH), 5.39–5.38 (m, 1H, CH), 4.65–4.64 (m, 1H, CH), 3.56 (d, J = 12.0 Hz, 1H, CH), 2.91 (t, J = 13.2 Hz, 1H, CH), 2.40 (d, J = 15.0 Hz, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 200.0, 196.9, 191.5, 188.5, 165.9, 142.1, 141.9, 139.8, 139.6, 138.5, 137.2, 136.8, 135.4, 133.9, 133.7, 132.3, 131.4, 130.3, 129.9, 129.3, 129.2, 128.9, 127.5, 127.2, 124.9, 123.7, 123.1, 121.6, 121.3, 100.0, 78.1, 76.8, 65.8, 63.3, 54.7, 29.7; IR (KBr) υ: 3278, 3066, 2914, 2836, 1741, 1703, 1584, 1464, 1431, 1265, 1132, 852, 746 cm–1; HRMS (ESI) calcd for C36H24BrN2O4([M + H]+): 627.0914, found: 627.0900.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(m-tolyl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2f)

White solid, 86%, mp 233–235 °C; 1H NMR (400 MHz, CDCl3) δ: 10.23 (s, 1H, NH), 7.93 (d, J = 7.6 Hz, 1H, Ar H), 7.76 (t, J = 7.2 Hz, 1H, Ar H), 7.72–7.69 (m, 2H, Ar H), 7.66 (d, J = 8.0 Hz, 1H, Ar H), 7.62 (d, J = 6.8 Hz, 1H, Ar H), 7.57–7.50 (m, 1H, Ar H), 7.44 (d, J = 7.6 Hz, 1H, Ar H), 7.32 (t, J = 7.6 Hz, 1H, Ar H), 7.28–7.25 (m, 1H, Ar H), 7.04–7.00 (m, 3H, Ar H), 6.92–6.89 (m, 2H, Ar H), 6.00 (s, 1H, CH), 5.45 (d, J = 3.6 Hz, 1H, CH), 4.63 (d, J = 4.0 Hz, 1H, CH), 3.55–3.52 (m, 1H, CH), 2.99–2.92 (m, 1H, CH), 2.39 (dd, J1 = 15.2 Hz, J2 = 2.0 Hz, 1H, CH), 2.20 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3) δ: 199.8, 197.5, 193.9, 188.7, 165.7, 143.0, 141.6, 139.9, 139.7, 137.5, 137.4, 136.0, 135.4, 134.9, 133.2, 132.8, 129.7, 129.1, 129.0, 128.5, 127.9, 127.8, 127.2, 125.1, 123.1, 123.0, 122.0, 121.2, 100.9, 77.3, 77.0, 76.7, 74.4, 67.8, 62.3, 56.3, 30.1, 21.4; IR (KBr) υ: 3273, 3099, 3018, 2918, 1741, 1706, 1570, 1489, 1461, 1365, 1278, 1137, 1062, 934, 868, 730, 700, 653 cm–1; HRMS (ESI) calcd for C37H26KN2O4([M + K]+): 601.1524, found: 601.1527.

2-(1,3-Bioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(3-fluorophenyl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2g)

White solid, 81%, mp 259–261 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.24 (s, 1H, NH), 7.95 (d, J = 7.6 Hz, 1H, Ar H), 7.82–7.70 (m, 4H, Ar H), 7.63–7.61 (m, 1H, Ar H), 7.58–7.54 (m, 2H, Ar H), 7.44 (d, J = 7.6 Hz, 1H, Ar H), 7.33 (t, J = 7.6 Hz, 1H, Ar H), 7.29–7.25 (m, 1H, Ar H), 7.16–7.12 (m, 1H, Ar H), 7.02–6.93 (m, 3H, Ar H), 6.85–6.80 (m, 1H, Ar H), 5.98 (s, 1H, CH), 5.39 (d, J = 3.6 Hz, 1H, CH), 4.64 (d, J = 4.4 Hz, 1H, CH), 3.51 (dd, J1 = 11.6 Hz, J2 = 2.4 Hz, 1H, CH), 2.94–2.87 (m, 1H, CH), 2.37 (dd, J1 = 15.2 Hz, J2 = 2.8 Hz, 1H, CH); 13C NMR (100 MHz, CDCl3) δ: 199.4, 197.3, 193.8, 188.8, 165.3, 162.4 (d, J = 244.5 Hz), 142.8, 141.4, 140.4, 140.3, 139.9, 139.7, 134.6, 133.3, 133.0, 129.5, 129.5, 129.2, 129.1, 128.0, 127.3, 123.7, 123.3, 123.2, 121.9, 121.2, 115.2 (d, J = 22.6 Hz), 114.1 (d, J = 20.9 Hz), 109.9, 100.8, 77.2, 74.3, 67.6, 62.7, 55.6, 30.1; IR (KBr) υ: 3280, 3067, 3020, 2916, 2838, 1742, 1709, 1659, 1589, 1488, 1202, 1090, 959, 828, 739 cm–1; HRMS (ESI) calcd for C36H24FN2O4([M + H]+): 567.1715, found: 567.1709.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(3-nitrophenyl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2h)

White solid, 82%, mp 252–254 °C; 1H NMR (400 MHz, CDCl3) δ: 10.18 (s, 1H, NH), 8.16–8.15 (m, 1H, Ar H), 8.04–8.01 (m, 1H, Ar H), 7.97 (d, J = 7.6 Hz, 1H, Ar H), 7.84–7.80 (m, 1H, Ar H), 7.78–7.74 (m, 1H, Ar H), 7.72–7.71 (m, 1H, Ar H), 7.60–7.53 (m, 4H, Ar H), 7.45 (d, J = 7.2 Hz, 1H, Ar H), 7.41–7.33 (m, 2H, Ar H), 7.30–7.26 (m, 1H, Ar H), 7.01 (d, J = 7.6 Hz, 1H, Ar H), 5.99 (s, 1H, CH), 5.44 (d, J = 3.6 Hz, 1H, CH), 4.73 (d, J = 4.0 Hz, 1H, CH), 3.53 (dd, J1 = 8.0 Hz, J2 = 2.4 Hz, 1H, CH), 2.91–4.84 (m, 1H, CH), 2.37 (dd, J1 = 14.8 Hz, J2 = 2.4 Hz, 1H, CH); 13C NMR (100 MHz, CDCl3) δ: 198.8, 197.2, 193.7, 189.0, 164.8, 147.8, 142.5, 141.3, 140.2, 139.8, 139.6, 136.6, 136.1, 134.4, 134.3, 133.4, 133.1, 129.4, 129.2, 129.0, 128.0, 127.4, 123.4, 123.3, 123.2, 122.2, 121.9, 121.3, 100.8, 77.2, 74.3, 67.6, 63.2, 55.0, 30.1; IR (KBr) υ: 3282, 3068, 2911, 2835, 1743, 1708, 1660, 1569, 1529, 1462, 1203, 994, 831, 737 cm–1; HRMS (ESI) calcd for C36H24N3O6([M + H]+): 594.1660, found: 594.1651.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(p-tolyl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2i)

White solid, 92%, mp 233–235 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.48 (s, 1H, NH), 7.97–7.95 (m, 1H, Ar H), 7.92–7.86 (m, 3H, Ar H), 7.68–7.62 (m, 4H, Ar H), 7.50 (d, J = 6.4 Hz, 1H, Ar H), 7.34 (t, J = 7.2 Hz, 1H, Ar H), 7.27 (t, J = 6.4 Hz, 1H, Ar H), 7.07 (d, J = 7.2 Hz, 1H, Ar H), 6.92–6.90 (m, 3H, Ar H), 5.96–5.95 (m, 1H, CH), 5.47–5.45 (m, 1H, CH), 4.37 (d, J = 4.0 Hz, 1H, CH), 3.18 (dd, J1 = 12.0 Hz, J2 = 2.4 Hz, 1H, CH), 2.64–2.57 (m, 1H, CH), 2.45–2.42 (m, 1H, CH), 2.16 (s, 3H, CH3); 13C NMR (100 MHz, DMSO-d6) δ: 200.5, 196.9, 192.0, 188.3, 166.7, 142.7, 141.3, 139.6, 139.5, 137.5, 136.7, 135.9, 135.7, 135.1, 133.9, 133.7, 130.3, 129.6, 129.4, 129.2, 128.7, 128.0, 127.3, 123.7, 123.3, 121.7, 121.2, 100.0, 77.3, 74.6, 67.6, 63.0, 55.4, 29.8, 21.0; IR (KBr) υ: 3275, 3018, 2918, 1738, 1704, 1569, 1459, 1357, 1274, 1135, 861, 740 cm–1; HRMS (ESI) calcd for C37H27N2O4([M + H]+): 563.1965, found: 563.1979.

3-(4-(Bimethylamino)phenyl)-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2j)

White solid, 73%, mp 262–264 °C; 1H NMR (400 MHz, CDCl3) δ: 10.35 (s, 1H, NH), 7.92–7.91 (m, 1H, Ar H), 7.74–7.69 (m, 4H, Ar H), 7.62–7.61 (m, 1H, Ar H), 7.53–7.52 (m, 2H, Ar H), 7.43–7.41 (m, 1H, Ar H), 7.32–7.30 (m, 2H, Ar H), 7.04–7.01 (m, 3H, Ar H), 6.54–6.51 (m, 2H, Ar H), 5.98 (s, 1H, CH), 5.34 (s, 1H, CH), 4.60 (s, 1H, CH), 3.51 (d, J = 12.4 Hz, 1H, CH), 2.96 (t, J = 10.4 Hz, 1H, CH), 2.84 (s, 6H, 2CH3), 2.37 (d, J = 13.2 Hz, 1H, CH); 13C NMR (100 MHz, CDCl3) δ: 200.1, 197.9, 194.1, 188.6, 166.0, 149.2, 143.1, 141.7, 139.9, 139.7, 135.9, 135.2, 135.0, 133.1, 132.7, 129.8, 129.1, 129.0, 128.8, 127.9, 127.2, 125.3, 123.2, 122.9, 122.0, 121.1, 112.1, 101.0, 77.1, 75.2, 68.0, 62.1, 56.0, 40.4, 30.2; IR (KBr) υ: 3270, 3071, 2903, 2832, 1744, 1708, 1665, 1568, 1520, 1459, 1362, 1340, 1246, 1058, 858, 743, 693 cm–1; HRMS (ESI) calcd for C38H29N3NaO4([M + Na]+): 614.2050, found: 614.2041.

3-(4-Bromophenyl)-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2k)

White solid, 81%, mp 278–281 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.46 (s, 1H, NH), 7.98–7.89 (m, 4H, Ar H), 7.73–7.71 (m, 1H, Ar H), 7.62–7.57 (m, 4H, Ar H), 7.36–7.30 (m, 3H, Ar H), 7.28 (t, J = 7.6 Hz, 1H, Ar H), 7.08–6.95 (m, 3H, Ar H), 5.93 (s, 1H, CH), 5.48 (s, 1H, CH), 4.36–4.35 (m, 1H, CH), 3.19 (d, J = 10.4 Hz, 1H, CH), 2.58 (t, J = 12.4 Hz, 1H, CH), 2.45–2.43 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 200.0, 196.9, 191.9, 191.9, 191.9, 188.5, 188.4, 188.4, 166.3, 142.6, 141.3, 138.4, 137.6, 136.9, 135.0, 133.9, 133.9, 133.8, 133.8, 133.8, 131.0, 130.4, 130.3, 129.7, 129.4, 129.2, 127.3, 123.8, 123.3, 120.0, 100.0, 77.4, 74.3, 67.5, 63.2, 54.9, 40.4, 40.2, 39.9, 29.9; IR (KBr) υ: 3279, 3066, 2902, 1738, 1704, 1569, 1488, 1279, 1137, 1003, 934, 862, 744 cm–1; HRMS (ESI) calcd for C36H23BrKN2O4([M + K]+): 665.0473, found: 665.0460.

3-(4-Chlorophenyl)-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2l)

White solid, 91%, mp 269–272 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.50 (s, 1H, NH), 8.02–8.00 (m, 2H, Ar H), 7.97–7.94 (m, 2H, Ar H), 7.75 (d, J = 7.2 Hz, 1H, Ar H), 7.70–7.68 (m, 2H, Ar H), 7.54 (d, J = 6.8 Hz, 1H, Ar H), 7.42–7.40 (m, 1H, Ar H), 7.33–7.29 (m, 2H, Ar H), 7.24–7.22 (m, 3H, Ar H), 7.12–7.08 (m, 2H, Ar H), 5.98 (s, 1H, CH), 5.54–5.50 (m, 1H, CH), 4.42–4.41 (m, 1H, CH), 3.24 (d, J = 10.8 Hz, 1H, CH), 2.64 (t, J = 12.4 Hz, 1H, CH), 2.49–2.47 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 200.0, 196.9, 191.9, 188.4, 166.3, 142.6, 141.3, 139.7, 139.5, 138.0, 137.6, 136.9, 135.0, 133.9, 133.7, 131.4, 130.3, 130.1, 129.7, 129.3, 129.2, 128.1, 127.3, 123.8, 123.3, 121.7, 121.3, 100.0, 77.4, 74.4, 67.6, 63.2, 54.9, 29.9; IR (KBr) υ: 3287, 3042, 2938, 1739, 1704, 1661, 1568, 1487, 1283, 1141, 1020, 936, 897, 732 cm–1; HRMS (ESI) calcd for C36H24ClN2O4([M + H]+): 583.1419, found: 583.1421.

3-(4-(tert-Butyl)phenyl)-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2m)

White solid, 81%, mp 255–257 °C; 1H NMR (400 MHz, CDCl3) δ: 10.35 (s, 1H, NH), 7.92 (d, J = 7.6 Hz, 1H, Ar H), 7.76–7.73 (m, 1H, Ar H), 7.71–7.65 (m, 2H, Ar H), 7.63–7.61 (m, 1H, Ar H), 7.58–7.56 (m, 1H, Ar H), 7.55–7.50 (m, 2H, Ar H), 7.44 (d, J = 7.2 Hz, 1H, Ar H), 7.33 (t, J = 7.2 Hz, 1H, Ar H), 7.29–7.25 (m, 1H, Ar H), 7.15–7.06 (m, 4H, Ar H), 7.03 (d, J = 7.6 Hz, 1H, Ar H), 6.01 (s, 1H, CH), 5.40–5.38 (m, 1H, CH), 4.63 (d, J = 4.0 Hz, 1H, CH), 3.55 (dd, J1 = 12.0 Hz, J2 = 2.4 Hz, 1H, CH), 3.03–2.96 (m, 1H, CH), 2.40 (dd, J1 = 15.6 Hz, J2 = 2.4 Hz, 1H, CH), 1.20 (s, 9H, 3CH3); 13C NMR (100 MHz, CDCl3) δ: 199.7, 197.6, 197.6, 194.0, 188.8, 165.7, 149.5, 143.1, 141.6, 139.9, 139.6, 135.8, 135.3, 135.0, 134.4, 133.1, 132.8, 129.7, 129.2, 129.0, 127.9, 127.7, 127.2, 124.9, 122.9, 122.0, 121.2, 100.9, 77.3, 74.7, 68.0, 61.8, 56.4, 34.3, 31.2, 30.1; IR (KBr) υ: 3280, 3063, 3019, 2960, 2872, 1741, 1703, 1569, 1461, 1356, 1274, 1136, 931, 824, 742 cm–1; HRMS (ESI) calcd for C40H33N2O4([M + H]+): 605.2435, found: 605.2432.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(4-nitrophenyl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2n)

White solid, 79%, mp 265–267 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.48 (s, 1H, NH), 8.12–8.00 (m, 4H, Ar H), 7.98–7.92 (m, 3H, Ar H), 7.74 (d, J = 7.6 Hz, 1H, Ar H), 7.70–7.65 (m, 3H, Ar H), 7.52 (d, J = 6.8 Hz, 1H, Ar H), 7.44–7.43 (m, 1H, Ar H), 7.38 (t, J = 7.2 Hz, 1H, Ar H), 7.32 (t, J = 7.6 Hz, 1H, Ar H), 7.11 (d, J = 7.6 Hz, 1H, Ar H), 6.00 (s, 1H, CH), 5.66 (s, 1H, CH), 4.56 (d, J = 3.6 Hz, 1H, CH), 3.26–3.25 (m, 1H, CH), 2.62 (t, J = 12.0 Hz, 1H, CH), 2.52–2.51 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.4, 196.7, 191.8, 188.6, 166.0, 147.0, 146.5, 142.4, 141.2, 139.6, 139.5, 137.8, 137.1, 134.9, 133.9, 133.8, 130.2, 129.7, 129.5, 129.4, 129.2, 127.3, 124.0, 123.4, 123.3, 121.7, 121.3, 99.9, 77.4, 74.0, 67.7, 63.6, 54.7, 29.9; IR (KBr) υ: 3245, 3017, 2900, 2832, 1741, 1704, 1571, 1571, 1460, 1206, 1050, 896, 789, 698 cm–1; HRMS (ESI) calcd for C36H23KN3O4([M + K]+): 632.1218, found: 632.1216.

3-(4-Chloro-2-hydroxyphenyl)-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2o)

White solid, 72%, mp 240–242 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.45 (s, 1H, NH), 9.44 (s, 1H, OH), 7.98–7.92 (m, 3H, Ar H), 7.88 (t, J = 7.2 Hz, 1H, Ar H), 7.75–7.73 (m, 1H, Ar H), 7.69–7.66 (m, 3H, Ar H), 7.55–7.54 (m, 2H, Ar H), 7.37 (t, J = 7.6 Hz, 1H, Ar H), 7.31 (t, J = 7.6 Hz, 1H, Ar H), 7.11 (d, J = 7.6 Hz, 1H, Ar H), 7.00–6.97 (m, 1H, Ar H), 6.45 (d, J = 8.8 Hz, 1H, Ar H), 5.98 (s, 1H, CH), 5.59 (s, 1H, CH), 4.61 (d, J = 3.6 Hz, 1H, CH), 3.24–3.21 (m, 1H, CH), 2.63–2.56 (m, 1H, CH), 2.40–2.37 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.4, 197.5, 191.8, 188.5, 167.0, 153.3, 142.2, 141.3, 139.7, 136.6, 136.5, 135.2, 133.7, 130.4, 129.8, 129.3, 129.2, 128.3, 127.3, 127.2, 123.3, 123.1, 122.6, 121.6, 115.9, 100.0, 77.8, 73.4, 65.7, 63.7, 48.3, 29.9; IR (KBr) υ: 3351, 3304, 3058, 2926, 1741, 1705, 1667, 1570, 1490, 1462, 1203, 1033, 928, 869, 787, 740, 700, 659 cm–1; HRMS (ESI) calcd for C36H24ClN2O5([M + H]+): 599.1368, found: 599.1364.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(furan-2-yl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2p)

White solid, 69%, mp 221–223 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.54 (s, 1H, NH), 8.08–8.04 (m, 3H, Ar H), 7.96–7.92 (m, 2H, Ar H), 7.75–7.71 (m, 3H, Ar H), 7.62–7.60 (m, 1H, Ar H), 7.39–7.34 (m, 2H, Ar H), 7.26–7.25 (m, 1H, Ar H), 7.12–7.11 (m, 1H, Ar H), 6.38–6.34 (m, 2H, Ar H), 5.97 (s, 1H, CH), 5.56 (s, 1H, CH), 4.50–4.48 (m, 1H, CH), 3.16–3.10 (m, 1H, CH), 2.60–2.58 (m, 1H, CH), 2.50–2.46 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.3, 195.7, 191.5, 188.2, 165.4, 152.3, 142.0, 141.2, 140.6, 139.2, 139.0, 137.2, 136.4, 134.3, 133.6, 133.4, 129.8, 129.2, 129.0, 128.8, 126.9, 123.5, 122.9, 121.3, 120.9, 110.5, 106.4, 99.6, 76.6, 72.5, 65.6, 62.7, 47.7, 39.5, 29.2; IR (KBr) υ: 3278, 3069, 2913, 2831, 1744, 1707, 1680, 1593, 1564, 1462, 1244, 1135, 888, 697 cm–1; HRMS (ESI) calcd for C34H23N2O5([M + H]+): 539.1601, found: 539.1620.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(thiophen-2-yl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2q)

White solid, 78%, mp 233–235 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.55 (s, 1H, NH), 8.06–8.04 (m, 1H, Ar H), 7.99–7.97 (m, 2H, Ar H), 7.94 (d, J = 8.0 Hz, 1H, Ar H), 7.82 (d, J = 8.0 Hz, 1H, Ar H), 7.69–7.67 (m, 3H, Ar H), 7.59–7.57 (m, 3H, Ar H), 7.37 (t, J = 8.0 Hz, 1H, Ar H), 7.32 (t, J = 7.6 Hz, 1H, Ar H), 7.21 (d, J = 4.4 Hz, 1H, Ar H), 7.11 (d, J = 7.6 Hz, 1H, Ar H), 6.87–6.86 (m, 2H, Ar H), 5.99 (s, 1H, CH), 5.53 (s, 1H, CH), 4.67 (d, J = 4.0 Hz, 1H, CH), 3.21–3.18 (m, 1H, CH), 2.62–2.59 (m, 1H, CH), 2.50–2.48 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 200.0, 196.2, 192.0, 188.3, 165.8, 142.8, 142.0, 141.4, 139.6, 139.5, 137.6, 136.8, 134.8, 134.0, 133.8, 130.2, 129.6, 129.4, 129.2, 127.3, 126.9, 125.5, 124.1, 123.8, 123.3, 121.7, 121.3, 100.1, 77.1, 75.6, 67.6, 63.0, 50.3, 29.8; IR (KBr) υ: 3277, 3068, 2915, 2836, 1742, 1705, 1568, 1462, 1245, 1203, 1060, 892, 738, 692 cm–1; HRMS (ESI) calcd for C34H23N3O2S ([M + H]+): 555.1373, found: 555.1383.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(pyridin-2-yl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2r)

White solid, 83%, mp 270–272 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.55 (s, 1H, NH), 8.07 (d, J = 7.6 Hz, 1H, Ar H), 8.01–7.94 (m, 4H, Ar H), 7.89 (d, J = 6.8 Hz, 1H, Ar H), 7.75 (d, J = 7.6 Hz, 1H, Ar H), 7.70–7.64 (m, 4H, Ar H), 7.55 (d, J = 6.8 Hz, 1H, Ar H), 7.37 (t, J = 7.6 Hz, 1H, Ar H), 7.30 (t, J = 7.6 Hz, 1H, Ar H), 7.13–7.09 (m, 2H, Ar H), 5.97 (s, 1H, CH), 5.91 (s, 1H, CH), 4.73 (d, J = 4.0 Hz, 1H, CH), 3.15–3.11 (m, 1H, CH), 2.48–2.45 (m, 1H, CH), 2.42–2.38 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.7, 197.7, 192.0, 188.7, 167.0, 158.6, 147.9, 147.9, 142.8, 141.4, 139.6, 139.5, 137.0, 136.5, 136.4, 134.7, 134.0, 133.8, 130.3, 129.6, 129.4, 129.2, 127.3, 123.9, 122.9, 122.4, 121.9, 121.7, 121.3, 100.0, 77.0, 77.0, 71.4, 67.5, 63.1, 55.8, 55.7, 29.8, 29.8; IR (KBr) υ: 3271, 3062, 2925, 1745, 1710, 1648, 1568, 1466, 1338, 1212, 935, 682 cm–1; HRMS (ESI) calcd for C35H24N3O4 ([M + H]+): 550.1761, found: 550.1769.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(pyridin-3-yl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2s)

White solid, 76%, mp 255–257 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.50 (s, 1H, NH), 8.33–8.32 (m, 1H, Ar H), 8.25–8.24 (m, 1H, Ar H), 8.02 (d, J = 7.2 Hz, 1H, Ar H), 7.99–7.92 (m, 3H, Ar H), 7.74–7.68 (m, 5H, Ar H), 7.55–7.53 (m, 1H, Ar H), 7.38 (t, J = 7.6 Hz, 1H, Ar H), 7.32 (t, J = 7.2 Hz, 1H, Ar H), 7.26–7.24 (m, 1H, Ar H), 7.12 (d, J = 7.6 Hz, 1H, Ar H), 5.99 (s, 1H, CH), 5.58 (s, 1H, CH), 4.43 (d, J = 3.2 Hz, 1H, CH), 3.28 (d, J = 12.0 Hz, 1H, CH), 2.66 (t, J = 12.0 Hz, 1H, CH), 2.54–2.51 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.7, 197.0, 191.8, 188.5, 166.1, 149.4, 148.1, 142.5, 141.3, 139.7, 139.5, 137.7, 137.1, 135.8, 135.0, 134.6, 133.9, 133.8, 130.2, 129.7, 129.4, 129.2, 127.3, 123.9, 123.3, 123.2, 121.7, 121.3, 99.9, 77.4, 74.2, 67.5, 63.3, 53.1, 29.8; IR (KBr) υ: 3284, 3070, 2969, 2916, 1741, 1704, 1571, 1484, 1202, 1089, 932, 713, 682, 618 cm–1; HRMS (ESI) calcd for C35H24N3O4([M + H]+): 550.1761, found: 550.1783.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(pyridin-4-yl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2t)

White solid, 74%, mp 265–267 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.50 (s, 1H, NH), 8.37–8.36 (m, 2H, Ar H), 8.05 (d, J = 6.8 Hz, 1H, Ar H), 8.01–7.95 (m, 3H, Ar H), 7.75 (t, J = 7.2 Hz, 1H, Ar H), 7.69–7.66 (m, 3H, Ar H), 7.55–7.53 (m, 1H, Ar H), 7.38 (t, J = 7.2 Hz, 1H, Ar H), 7.32 (t, J = 7.2 Hz, 1H, Ar H), 7.12–7.10 (m, 3H, Ar H), 5.98 (s, 1H, CH), 5.66 (s, 1H, CH), 4.41 (d, J = 3.2 Hz, 1H, CH), 3.24 (d, J = 11.2 Hz, 1H, CH), 2.59 (t, J = 11.6 Hz, 1H, CH), 2.49–2.48 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.5, 196.6, 191.8, 188.6, 166.1, 149.6, 147.8, 142.5, 141.2, 139.6, 137.8, 137.1, 134.9, 133.9, 133.8, 130.2, 129.7, 129.4, 129.2, 127.3, 124.0, 123.4, 123.2, 121.7, 121.3, 99.9, 77.3, 73.0, 67.4, 63.4, 54.2, 29.8; IR (KBr) υ: 3293, 3071, 3038, 2901, 2834, 1742, 1705, 1668, 1567, 1461, 1203, 1140, 1054, 892, 815, 740, 680 cm–1; HRMS (ESI) calcd for C35H24N3O4 ([M + H]+): 550.1761, found: 550.1783.

3-Benzoyl-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2u)

White solid, 85%, mp 284–286 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.68 (s, 1H, NH), 8.18 (d, J = 7.6 Hz, 1H, Ar H), 8.10–8.05 (m, 3H, Ar H), 7.99–7.91 (m, 4H, Ar H), 7.82 (d, J = 6.4 Hz, 1H, Ar H), 7.63–7.58 (m, 6H, Ar H), 7.52 (t, J = 7.2 Hz, 2H, Ar H), 7.41 (t, J = 7.2 Hz, 2H, Ar H), 7.30 (d, J = 7.6 Hz, 1H, Ar H), 6.26 (s, 1H, CH), 6.10 (s, 1H, CH), 5.27 (d, J = 3.6 Hz, 1H, CH), 3.40–3.37 (m, 1H, CH), 2.68–2.65 (m, 1H, CH), 2.61–2.57 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.5, 196.7, 193.8, 191.8, 189.4, 166.4, 141.5, 140.8, 139.8, 139.4, 137.5, 136.9, 136.5, 134.6, 134.0, 133.9, 133.3, 130.2, 129.8, 129.4, 129.1, 128.8, 128.2, 127.3, 123.6, 123.2, 121.8, 121.3, 99.7, 77.6, 69.7, 64.9, 64.7, 55.8, 29.6; IR (KBr) υ: 3239, 3065, 2913, 2828, 1739, 1708, 1653, 1580, 1461, 1266, 1144, 792, 704, 637 cm–1; HRMS (ESI) calcd for C37H25N2O5 ([M + H]+): 577.1758, found: 577.1765.

6-Bromo-3-(4-chlorophenyl)-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2v)

White solid, 81%, mp 266–268 °C; 1H NMR (600 MHz, DMSO-d6) δ: 10.56 (s, 1H, NH), 8.04 (d, J = 7.8 Hz, 1H, Ar H), 8.01 (d, J = 7.8 Hz, 1H, Ar H), 7.97 (d, J = 7.8 Hz, 1H, Ar H), 7.93 (d, J = 7.2 Hz, 1H, Ar H), 7.73 (d, J = 7.8 Hz, 1H, Ar H), 7.71–7.67 (m, 4H, Ar H), 7.56 (d, J = 7.2 Hz, 1H, Ar H), 7.38 (t, J = 7.8 Hz, 1H, Ar H), 7.24–7.23 (m, 2H, Ar H), 7.12–7.11 (m, 1H, Ar H), 6.00 (s, 1H, CH), 5.51 (s, 1H, CH), 4.40 (d, J = 3.6 Hz, 1H, CH), 3.29 (dd, J1 = 11.4 Hz, J2 = 2.4 Hz, 1H, CH), 2.61–2.58 (m, 1H, CH), 2.53–2.52 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.5, 196.8, 191.6, 188.4, 165.9, 134.6, 132.8, 131.4, 130.1, 129.6, 128.9, 127.9, 124.3, 123.8, 123.2, 100.0, 77.0, 74.5, 67.1, 62.2, 55.4, 30.9; IR (KBr) υ: 3288, 3066, 2927, 1738, 1702, 1652, 1571, 1492, 1452, 1280, 1136, 1012, 892, 819, 779, 698 cm–1; HRMS (ESI) calcd for C36H22BrClN2NaO4 ([M + Na]+): 683.0344, found: 683.0351.

6-Bromo-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-(4-nitrophenyl)-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2w)

White solid, 83%, mp 275–277 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.59 (s, 1H, NH), 8.08–8.03 (m, 4H, Ar H), 7.99 (t, J = 7.2 Hz, 1H, Ar H), 7.93 (t, J = 7.2 Hz, 1H, Ar H), 7.74 (d, J = 7.6 Hz, 1H, Ar H), 7.67–7.65 (m, 3H, Ar H), 7.61–7.60 (m, 2H, Ar H), 7.40–7.35 (m, 3H, Ar H), 5.99 (s, 1H, CH), 5.62 (s, 1H, CH), 4.53 (d, J = 3.6 Hz, 1H, CH), 3.31 (dd, J1 = 11.2 Hz, J2 = 2.4 Hz, 1H, CH), 2.61–2.58 (m, 1H, CH), 2.48–2.44 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 199.2, 196.8, 165.8, 147.0, 146.5, 142.4, 141.2, 139.7, 137.8, 137.2, 134.6, 133.7, 133.0, 129.7, 129.7, 129.1, 124.4, 124.1, 123.4, 123.3, 121.3, 100.1, 78.0, 77.9, 77.9, 74.5, 67.5, 62.7, 55.4, 31.1; IR (KBr) υ: 3288, 3074, 2912, 1744, 1704, 1658, 1578, 1518, 1421, 1214, 1011, 942, 839, 706, 690 cm–1; HRMS (ESI) calcd for C36H22BrKN3O6 ([M + K]+): 710.0324, found: 710.0319.

2-(1,3-Dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-hexyl-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2x)

White solid, 70%, mp 275–277 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.52 (s, 1H, NH), 8.10–8.03 (m, 4H, Ar H), 7.86 (t, J = 8.0 Hz, 1H, Ar H), 7.71–7.70 (m, 4H, Ar H), 7.35 (t, J = 7.6 Hz, 1H, Ar H), 7.28 (d, J = 7.2 Hz, 1H, Ar H), 7.08 (d, J = 7.2 Hz, 1H, Ar H), 5.86(s, 1H, CH), 4.70 (s, 1H, CH), 3.19 (d, J = 12.0 Hz, 1H, CH), 2.97 (d, J = 11.6 Hz, 1H, CH), 2.70–2.69 (m, 1H, CH), 2.49–2.46 (m, 1H, CH), 2.37 (d, J = 10.8 Hz, 1H, CH), 1.99–1.91 (m, 1H, CH), 1.10–1.05 (m, 2H, CH), 0.96–0.94 (m, 4H, CH), 0.79–0.78 (m, 1H, CH), 0.69 (t, J = 5.6 Hz, 3H, CH3), 0.51–0.50 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 200.8, 198.3, 192.3, 188.9, 167.1, 142.3, 140.3, 139.7, 139.3, 137.6, 137.1, 134.7, 134.0, 133.8, 130.2, 129.4, 129.1, 127.3, 123.9, 123.3, 121.7, 121.3, 100.2, 76.9, 76.7, 65.0, 64.3, 49.3, 31.1, 31.0, 29.6, 28.4, 28.1, 21.8, 14.1; IR (KBr) υ: 3237, 3071, 2952, 2849, 1741, 1703, 1647, 1593, 1493, 1359, 1334, 1273, 1203, 1002, 897, 785, 737, 685 cm–1; HRMS (ESI) calcd for C36H32N2NaO4([M + Na]+): 579.2254, found: 579.2254.

6-Bromo-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-3-hexyl-1,2a,3,4a,5,9b-hexahydro-2H-spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2′-indene]-1′,3′-dione (2y)

White solid, 63%, mp 251–253 °C; 1H NMR (400 MHz, DMSO-d6) δ: 10.54 (s, 1H, NH), 8.12–8.04 (m, 4H, Ar H), 7.95 (t, J = 7.2 Hz, 1H, Ar H), 7.72–7.70 (m, 4H, Ar H), 7.62 (d, J = 7.6 Hz, 1H, Ar H), 7.33 (t, J = 7.2 Hz, 1H, Ar H), 5.86(s, 1H, CH), 4.71 (s, 1H, CH), 3.21 (d, J = 11.6 Hz, 1H, CH), 3.01 (d, J = 11.2 Hz, 1H, CH), 2.68–2.66 (m, 1H, CH), 2.41 (d, J = 15.0 Hz, 1H, CH), 2.33 (d, J = 12.4 Hz, 1H, CH), 1.98–1.95 (m, 1H, CH), 1.09–1.06 (m, 2H, CH), 0.96–0.92 (m, 4H, CH), 0.80–0.78 (m, 1H, CH), 0.70 (t, J = 5.6 Hz, 3H, CH3), 0.52–0.50 (m, 1H, CH); 13C NMR (100 MHz, DMSO-d6) δ: 200.6, 198.2, 192.2, 188.9, 166.9, 142.2, 140.4, 139.7, 139.3, 137.7, 137.2, 134.2, 134.0, 133.8, 133.0, 132.9, 129.4, 129.1, 124.5, 124.0, 123.3, 121.7, 121.3, 100.4, 76.7, 64.8, 63.8, 49.7, 31.1, 31.0, 30.8, 28.4, 28.1, 21.8, 14.1; IR (KBr) υ: 3247, 3071, 2925, 2853, 1742, 1707, 1669, 1569, 1451, 1359, 1276, 1215, 1090, 953, 833, 777, 696, 652 cm–1; HRMS (ESI) calcd for C36H32BrN2NaO4([M + H]+): 635.1540, found: 635.1544.