Synthesis of pyrano[3,2-c]quinolones and furo[3,2-c]quinolones via acid-catalyzed tandem reaction of 4-hydroxy-1-methylquinolin-2(1H)-one and propargylic alcohols

Abstract

Two acid-catalyzed tandem reactions between 4-hydroxy-1-methylquinolin-2(1H)-one and propargylic alcohols are described. Depending mainly on the propargylic alcohol used, these tandem reactions proceed via either a Friedel–Crafts-type allenylation followed by 6-endo-dig cyclization sequence to form pyrano[3,2-c]quinolones or a Friedel–Crafts-type alkylation and 5-exo-dig ring closure sequence to afford furo[3,2-c]quinolones in moderate-to-high yields. The pyrano[3,2-c]quinolones products could be further transformed to tetracyclic 4,9-dihydro-5H-cyclopenta[lmn]phenanthridin-5-one derivatives.

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Introduction

Pyrano[3,2-c]quinolone is a structural motif occurring in a number of natural products¹ with a wide range of important biological activities such as anticancer,² antibacterial,² antimalarial,³ antiinflammatory⁴ and antifungal⁵ properties and inhibition of calcium signaling,⁶ TNF-α,⁷ platelet aggregation,⁸ and nitric oxide production.⁹ For example, alkaloids zanthosimuline and huajiaosimuline¹⁰ exhibit cytotoxicity against cancer cells, which is considered as potential anticancer agents (Scheme 1a). In addition, furo[3,2-c]quinolone derivatives such as araliopsine and almein are principally isolated from Rutaceae species¹¹ (Scheme 1a). Furo[3,2-c]quinolone hybrids are a significant class of angularly fused tricyclic compounds among the great variety of furan derivatives, which have been shown to exhibit biological and pharmacological activity such as antimicrobial, insecticidal, antiarrhythmic, antimalarial, antiplatelet aggregation and sedative,^1,12 photochemical treatment in clinic therapeutic field¹³ and blocking activities of the voltage-gated potassium channel Kv1.3.¹⁴ Consequently, a large number of procedures have been developed for the construction of these highly useful structures.¹⁵ However, current methods more or less suffer from limited substrate scope, complicated catalyst or noble metal catalyst systems, not easily accessible starting materials, or multistep manipulations, the development of simple methods with wide product diversity is still highly desirable. Propargylic alcohols are readily accessible synthetic building blocks in organic synthesis.¹⁶ Over the past few decades, the development of Lewis acid-catalyzed tandem annulations of propargylic alcohols has attracted interests from synthetic chemists, especially for the construction of various heterocyclic skeletons including pyrroles,¹⁷ furans,¹⁸ pyrans,¹⁹ carbazoles,²⁰ quinolines,²¹ and tetrahydro-β-carbolines.²² We herein describe the development of acid-catalyzed formal [3 + 3]/[3 + 2] cascade annulation processes for the construction of pyrano[3,2-c]quinolone/furo[3,2-c]quinolone derivatives from 4-hydroxy-1-methylquinoline-2(1H)-one and propargylic alcohols (Scheme 1b).

Scheme 1 Representative natural products with pyrano[3,2-c]quinolone or furo[3,2-c]quinolone skeleton.

Results and discussion

Our initial studies commenced with the reaction of 4-hydroxy-1-methylquinolin-2(1H)-one 1 and propargylic alcohol 2a (Table 1). No reaction occurred in the absence of an acid catalyst (Table 1, entry 1). Using 1,2-DCE (1,2-dichloroethane) as solvent, five Lewis acid catalysts and four Brønsted acid catalysts were screened and pTsOH·H₂O was found to be the most efficient one for this reaction (Table 1, entries 2–10). The product 3a could be isolated in only 5% yield when the reaction was performed at 25 °C (Table 1, entry 11). Changing the solvent to THF, toluene, DMF (N,N-dimethylformamide) gave inferior results (Table 1, entries 12–14). Further screening of catalyst loading amount uncovered that 10 mol% was optimal for the reaction, while lower (5 mol%) or higher (20 mol%) loadings all led to no improvement in yields (Table 1, entries 15–16). Notably, relatively lower yields yet shorter reaction time were observed in the cases of metal Lewis acid catalysts, which might be due to faster decomposition of the propargylic alcohol 2a under these conditions as observed by thin-layer chromatography (Table 1, entries 2–10). Moreover, it is worth mentioning that the reaction is tolerant of moisture and could be performed under air.

Table 1 Screening of the reaction conditions^a,b

Entry	Catalyst (mol%)	Solvent	Time	Yield^b (%)
a Reaction conditions: 1 (0.5 mmol), 2a (0.5 mmol), solvent (5 mL), under air, the reaction was monitored by TLC.b Yield of the isolated product.c Reaction was run at 25 °C.d Reaction was run at 66 °C.e Reaction was run at 90 °C.
1	No catalyst	1,2-DCE	24 h	0
2	Yb(OTf)3 (10)	1,2-DCE	0.5 h	23
3	Sc(OTf)3 (10)	1,2-DCE	0.5 h	25
4	Zn(OTf)2 (10)	1,2-DCE	0.5 h	23
5	Cu(OTf)2 (10)	1,2-DCE	0.5 h	35
6	FeCl3·6H2O (10)	1,2-DCE	0.5 h	20
7	pTsOH·H2O (10)	1,2-DCE	1 h	70
8	CH3COOH (10)	1,2-DCE	36 h	0
9	TFA (10)	1,2-DCE	36 h	40
10	TfOH (10)	1,2-DCE	1 h	57
11^c	pTsOH·H2O (10)	1,2-DCE	36 h	5
12^d	pTsOH·H2O (10)	THF	36 h	35
13^e	pTsOH·H2O (10)	Toluene	4 h	34
14^e	pTsOH·H2O (10)	DMF	24 h	0
15	pTsOH·H2O (5)	1,2-DCE	4 h	50
16	pTsOH·H2O (20)	1,2-DCE	1 h	65

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With the optimized reaction conditions (Table 1, entry 7) in hand, a series of propargylic alcohols 2 were reacted with 4-hydroxy-1-methylquinolin-2(1H)-one 1 to examine the reaction scope with regard to the formation of pyrano[3,2-c]quinolone 3. As depicted in Scheme 2, the transformation of various substituted propargylic alcohols 2 proceeded smoothly to deliver the corresponding pyrano[3,2-c]quinolone derivatives in moderate to good yields, irrespective of the electronic nature of the substituents. A variety of functional groups, including methyl, methoxyl, halogen and cyclopropyl substituents, were compatible with the reaction. Notably, cyclopropyl ring has a wide range of applications in drug molecular design²³ and propargylic alcohol bearing cyclopropyl was tolerated in the reaction conditions to generate the desired product 3i in 58% yield. In addition, other alkyl groups (R¹) such as methyl, n-butyl and trimethylsilyl also gave [3 + 3] products 3t–3u in 51–57% yields. Moreover, when 9-fluorenyl-substituted propargylic alcohols 2q–2s were subjected to the reaction conditions, spirocyclic products 3q–3s could be formed in the yields of 24–55% albeit with much prolonged reaction time of 10 h. It was found that product 3x was produced by hydroamination of N–H in 1 with alkyne in 2 beside normal product 3w. Then products 3y and 3z were synthesized by adjusting molar ratio of the reaction. The structure of the products 3a and 3z was additionally confirmed by X-ray crystallographic analysis (see ESI† for details).

Scheme 2 Scope study with different propargylic alcohols 2^a,b. ^aReaction conditions: 1 (0.5 mmol), 2 (0.5 mmol), pTsOH·H₂O (0.05 mmol), 1,2-DCE (5 mL), 84 °C. ^bIsolated yield refers to pyrano[3,2-c]quinolone derivatives. ^cReaction time: 10 h. ^dReaction time: 10 min. ^eReaction conditions: 1 (0.5 mmol), 2 (1.0 mmol), pTsOH·H₂O (0.05 mmol), 1,2-DCE (5 mL), 84 °C.

Based on the above experimental results, a plausible mechanism for the present cascade reactions is proposed (Scheme 3). First, in the presence of a Brønsted acid catalyst, propargylic alcohol 2a is converted to the propargylic carbocation I, which is in equilibrium with the allenic form II.²⁴ The latter would undergo Friedel–Crafts-type reaction with 1 to form the allene intermediate III, which would be transformed to the final product 3a via 6-endo-dig cyclization.^19f

Scheme 3 A possible mechanism for the dehydrative annulation.

To further extend the scope of the current reaction, secondary propargylic alcohols 2u was tested as substrate. Unexpectedly, 3-(1,3-diphenylprop-2-yn-1-yl)-4-hydroxy-1-methylquinolin-2(1H)-one 5a was isolated instead of the desired pyrano[3,2-c]quinolone 3u under the above optimized reaction conditions (Scheme 4). Given the recent reports on transition-metal-catalyzed direct heterocyclization of alkynes to construct furan frameworks,²⁵ Cu(OTf)₂ was then used to catalyze the reaction and to our delight, the ring-closure compound furo[3,2-c]quinolone 4a was isolated as expected in 48% yield (Table 2, entry 2). Different Lewis acid catalysts were then screened (Table 2, entries 1–10), and CuOTf was found to be one of the best choice (Table 2, entry 3), while some catalysts could not transform 5a to 4a accordingly (Table 2, entries 1 and 4–7), indicating that the reactions were stuck at the stage of 5a. The reaction hardly occurred at room temperature (Table 2, entry 8). The use of other solvents including THF, toluene, DMF or changing the catalyst loadings made no improvement in yield (Table 2, entries 11–16).

Scheme 4 Synthesis of 5a catalyzed by pTsOH·H₂O.

Table 2 Screening of the reaction conditions^a

Entry	Catalyst (mol%)	Solvent	Time	Yield^b (%)
				4a	5a
a Reaction conditions: 1 (0.5 mmol), 2u (0.5 mmol), solvent (5 mL), under air, the reaction was monitored by TLC.b Yield of the isolated product.c Reaction was run at 25 °C.d Reaction was run at 66 °C.e Reaction was run at 90 °C.
1	pTsOH·H2O (10)	1,2-DCE	10 h	0	52
2	Cu(OTf)2 (10)	1,2-DCE	10 h	48	0
3	CuOTf (10)	1,2-DCE	10 h	60	0
4	Yb(OTf)3 (10)	1,2-DCE	24 h	0	51
5	Zn(OTf)2 (10)	1,2-DCE	24 h	0	53
6	FeCl3·6H2O (10)	1,2-DCE	24 h	0	55
7	HAuCl4·3H2O (10)	1,2-DCE	24 h	0	Trace
8	CuCl (10)	1,2-DCE	24 h	0	0
9	CuBr (10)	1,2-DCE	24 h	0	0
10	CuOAc (10)	1,2-DCE	24 h	0	0
11^c	CuOTf (10)	1,2-DCE	24 h	0	0
12^d	CuOTf (10)	THF	10 h	31	0
13^e	CuOTf (10)	Toluene	10 h	34	0
14^e	CuOTf (10)	DMF	10 h	30	0
15	CuOTf (5)	1,2-DCE	10 h	20	0
16	CuOTf (20)	1,2-DCE	10 h	51	0

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Next, the scope of the reaction with regard to the propargylic alcohols was investigated under the optimized reaction conditions, and the results were presented in Scheme 5. In general, the products 4 were produced in low to moderate yields (31–60%), regardless of the electronic nature and/or position of the substituents on the benzene rings (R¹ or R²). It was worth noting that only stereodefined (Z)-furo[3,2-c]quinolones had been isolated. The structure of the product 4g was additionally confirmed by X-ray crystallographic analysis (see ESI† for details). The primary alcohol such as 3-phenylprop-2-yn-1-ol was tested under the same reaction conditions for 24 hours, but no new product was detected and the staring material was recovered in 95% yield. Primary alcohol may not easily form primary carbocation under this reaction conditions.

Scheme 5 Scope study with secondary propargylic alcohols^a,b. ^aReaction conditions: 1 (0.5 mmol), 2 (0.5 mmol), CuOTf (0.05 mmol), 1,2-DCE (5 mL), 84 °C. ^bIsolated yield refers to furo[3,2-c]quinolones.

To gain some insight into the reaction mechanism of this formal [3 + 2] annulation, some controlled experiments were conducted (Scheme 6a). Quenching the reaction between 1 and propargylic alcohols 2u at an early stage (1 hour) gave the compound 5a as the major product in 60% yield, indicating the Friedel–Crafts-type reaction was a relatively fast step in this process. Treatment of the isolated 5a under the otherwise same reaction conditions produced the final product 4a in 80% yield after 10 hours. On the basis of these results and literature reports,^25b,f a mechanistic proposal for the conversion of 5a to 4a is depicted (Scheme 6b). The transformation began with the coordination of the triple bond to the copper(I) salt to facilitate the highly regioselective 5-exo-dig nucleophilic attack of the hydroxy group to form the intermediate B. Finally, protonolysis of B afforded 4a and regenerated the catalyst.

Scheme 6 Controlled experiments and mechanistic proposal for the [3 + 2]-annulation.

To demonstrate the practicality of this formal [3 + 3] cascade annulation, a gram-scale experiment was carried out to provide desired product 3a in 73% yield (Scheme 7a). Furthermore, novel tetracyclic compounds 6a–6e were forged from 3a and propargylic alcohols 2 in 41–60% yields, which proceeded via sequential Diels–Alder reaction of 2H-pyran with alkynes followed by retro-Diels–Alder extrusion of benzophenone under thermal reaction conditions and Friedel–Crafts-type reaction at last.²⁶ Furo[3,2-c]quinolones 4 could be isomerized to 7 under the catalysis pTsOH·H₂O with excellent yields (Scheme 7b). The structure of the product 6a was additionally confirmed by X-ray crystallographic analysis (see ESI† for details).

Scheme 7 Scale-up reaction and product transformations.

Conclusions

In conclusion, novel acid-catalyzed annulation reactions of propargylic alcohols with 4-hydroxy-1-methylquinolin-2(1H)-one were developed. This method provides a good atom- and step-economic way to useful pyrano[3,2-c]quinolone and furo[3,2-c]quinolone derivatives in moderate to good yields from readily accessible starting materials. Efforts towards the utilization of the propargylic alcohols to the synthesis of other useful cyclic compounds are underway in our laboratories.

Experimental section

General comments

Infrared spectra were obtained on a FTIR spectrometer. ¹H NMR spectra were recorded on 400 MHz spectrometer in CDCl₃ solution and the chemical shifts were reported relative to internal standard TMS (0 ppm). The following abbreviations are used to describe peak patterns where appropriate: br = broad, s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet. Coupling constants are reported in Hertz (Hz). ¹³C NMR were recorded on 100 MHz and referenced to the internal solvent signals (central peak is 77.00 ppm in CDCl₃). HRMS data were obtained using ESI ionization. Melting points were measured with micro melting point apparatus.

The propargylic alcohols 2 were prepared from phenylacetylene and benzophenone according to published methods.²⁷ Solvents were distilled prior to use. All chemicals were used as purchased unless otherwise mentioned.

General procedure for the synthesis of 3

A solution of 4-hydroxy-1-methylquinolin-2(1H)-one 1 (0.5 mmol), propargylic alcohols 2 (0.5 mmol) and pTsOH·H₂O (0.05 mmol) in 1,2-DCE (5 mL) was stirred under air at 84 °C for 1 h. After being cooled down to room temperature, the solvent was evaporated and the crude product was purified by silica gel column chromatography with petroleum ether/ethyl acetate (2 : 1, v/v).

General procedure for the synthesis of 4

A solution of 4-hydroxy-1-methylquinolin-2(1H)-one 1 (0.5 mmol), the secondary propargylic alcohols 2 (0.5 mmol) and CuOTf (0.05 mmol) in 1,2-DCE (5 mL) was stirred under air at 84 °C for 10 h. After being cooled down to room temperature, the solvent was evaporated and the crude product was purified by silica gel column chromatography with petroleum ether/ethyl acetate (2 : 1, v/v).

Synthesis of 5a

A solution of 4-hydroxy-1-methylquinolin-2(1H)-one 1 (0.5 mmol), propargylic alcohols 2u (0.5 mmol) and CuOTf (0.05 mmol) in DCE (5 mL) was stirred under air at 84 °C for 1 h. After being cooled down to room temperature, the solvent was evaporated and the crude product was purified by silica gel column chromatography with petroleum ether/ethyl acetate (1 : 1, v/v).

General procedure for the synthesis of 6

A solution of pyrano[3,2-c]quinolone 3a (0.5 mmol), propargylic alcohols 2 (0.6 mmol) and Yb(OTf)₃ (0.05 mmol) in 1,2-DCE (5 mL) was stirred under air at 84 °C for 4 h. After being cooled down to room temperature, the solvent was evaporated and the crude product was purified by silica gel column chromatography with petroleum ether/ethyl acetate (3 : 1, v/v).

General procedure for the synthesis of 7

A solution of furo[3,2-c]quinolones 4 (0.2 mmol) and pTsOH·H₂O (0.04 mmol) in 1,2-DCE (3 mL) was stirred under air at 84 °C for 12 h. After being cooled down to room temperature, the solvent was evaporated and the crude product was purified by silica gel column chromatography with petroleum ether/ethyl acetate (2 : 1, v/v).

Gram-scale synthesis for product 3a

A solution of 4-hydroxy-1-methylquinolin-2(1H)-one 1 (4.0 mmol), propargylic alcohols 2a (4.0 mmol) and pTsOH·H₂O (0.4 mmol) in 1,2-DCE (20 mL) was stirred under air at 84 °C for 1 h. After being cooled down to room temperature, the solvent was evaporated and the crude product was purified by silica gel column chromatography with petroleum ether/ethyl acetate (2 : 1, v/v).

Characterization data of products

6-Methyl-2,2,4-triphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3a). White solid (155 mg, 70%); mp 217–218 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.22 (d, J = 8.2 Hz, 1H), 7.61–7.47 (m, 5H), 7.44–7.20 (m, 13H), 5.96 (s, 1H), 3.54 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.60, 156.52, 143.67, 139.88, 139.55, 135.74, 131.31, 128.17, 127.84, 127.66, 127.32, 127.24, 126.80, 126.10, 123.53, 121.75, 115.89, 113.98, 108.19, 84.31, 29.20. IR (KBr) ν 3022, 1649, 1557, 1489, 1393, 1116, 990, 756, 698 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₃NO₂ + H]⁺): 442.1802; found: 442.1801.

6-Methyl-2,2-diphenyl-4-(p-tolyl)-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3b). White solid (155 mg, 68%); mp 192–193 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.21 (dd, J = 8.3, 1.4 Hz, 1H), 7.65–7.43 (m, 5H), 7.41–7.21 (m, 10H), 7.16 (d, J = 7.9 Hz, 2H), 5.94 (s, 1H), 3.54 (s, 3H), 2.36 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.67, 156.52, 143.73, 139.87, 136.85, 136.62, 135.61, 131.28, 128.44, 128.16, 127.82, 127.17, 126.83, 125.73, 123.54, 121.76, 115.94, 113.99, 108.29, 84.31, 29.23, 21.28. IR (KBr) ν 3025, 2920, 1732, 1648, 1556, 1447, 1389, 1113, 988, 752, 700 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₂H₂₅NO₂ + H]⁺): 456.1958; found: 456.1960.

4-(4-Methoxyphenyl)-6-methyl-2,2-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3c). White solid (111 mg, 47%); mp 199–200 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.21 (dd, J = 8.1, 1.5 Hz, 1H), 7.58–7.46 (m, 5H), 7.36–7.20 (m, 10H), 6.95–6.84 (m, 2H), 5.92 (s, 1H), 3.81 (s, 3H), 3.54 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.68, 158.84, 156.57, 143.75, 139.85, 135.27, 131.86, 131.29, 128.45, 128.15, 127.81, 126.81, 125.41, 123.53, 121.76, 115.94, 113.98, 113.13, 108.25, 84.30, 55.13, 29.23. IR (KBr) ν 3058, 2837, 1652, 1557, 1499, 1384, 1113, 988, 756, 700 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₂H₂₅NO₃ + H]⁺): 472.1907; found: 472.1905.

4-(2-Fluorophenyl)-6-methyl-2,2-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3d). White solid (142 mg, 62%); mp 196–197 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.19 (d, J = 7.2 Hz, 1H), 7.57–7.49 (m, 5H), 7.42 (t, J = 7.5 Hz, 1H), 7.36–7.20 (m, 9H), 7.16 (t, J = 7.5 Hz, 1H), 7.05 (t, 1H), 6.01 (s, 1H), 3.52 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.87 (d, J_C–F = 244.6 Hz), 159.86, 155.48, 143.60, 139.78, 131.31, 130.13, 129.60 (d, J_C–F = 3.7 Hz), 129.01 (d, J_C–F = 8.1 Hz), 128.24, 127.92, 127.74, 127.28, 126.83, 123.70 (d, J_C–F = 3.3 Hz), 123.56, 121.78, 115.86, 114.73 (d, J_C–F = 21.6 Hz), 114.00, 108.18, 84.05, 29.19; ¹⁹F NMR (377 MHz, CDCl₃) δ −114.21 (m). IR (KBr) ν 3061, 1736, 1649, 1559, 1489, 1394, 1124, 993, 753, 699 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₂FNO₂ + H]⁺): 460.1707; found: 460.1709.

4-(3-Fluorophenyl)-6-methyl-2,2-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3e). White solid (218 mg, 95%); mp 194–195 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.22 (dd, J = 8.1, 1.3 Hz, 1H), 7.61–7.53 (m, 1H), 7.53–7.46 (m, 4H), 7.36–7.22 (m, 9H), 7.15 (d, J = 7.7 Hz, 1H), 7.13–7.06 (m, 1H), 7.00 (td, J = 8.4, 2.1 Hz, 1H), 5.97 (s, 1H), 3.54 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.27 (d, J_C–F = 243.5 Hz), 159.50, 156.68, 143.47, 141.84 (d, J_C–F = 8.0 Hz), 139.93, 134.79 (d, J_C–F = 2.0 Hz), 131.54, 129.05 (d, J_C–F = 8.2 Hz), 128.26, 127.97, 126.77, 126.61, 123.61, 123.18 (d, J_C–F = 2.7 Hz), 121.91, 115.82, 114.50 (d, J_C–F = 21.8 Hz), 114.10 (d, J_C–F = 20.9 Hz), 114.09, 107.86, 84.35, 29.24; ¹⁹F NMR (377 MHz, CDCl₃) δ −114.10 (m). IR (KBr) ν 3061, 2943, 1732, 1645, 1559, 1486, 1395, 1115, 756, 698 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₂FNO₂ + H]⁺): 460.1707; found: 460.1709.

4-(4-Fluorophenyl)-6-methyl-2,2-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3f). White solid (140 mg, 61%); mp 210–211 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.22 (d, J = 8.1 Hz, 1H), 7.60–7.45 (m, 5H), 7.39–7.21 (m, 10H), 7.04 (t, J = 8.7 Hz, 2H), 5.93 (s, 1H), 3.53 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.15 (d, J_C–F = 244.1 Hz), 159.64, 156.67, 143.57, 139.88, 135.47 (d, J_C–F = 3.3 Hz), 134.85, 131.48, 128.94 (d, J_C–F = 8.0 Hz), 128.23, 127.93, 126.77, 126.10, 123.59, 121.89, 115.85, 114.6 (d, J_C–F = 21.4 Hz), 114.06, 107.94, 84.32, 29.22; ¹⁹F NMR (377 MHz, CDCl₃) δ −115.24 (s). IR (KBr) ν 3058, 2925, 1646, 1556, 1509, 1388, 1118, 988, 755, 701 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₂FNO₂ + H]⁺): 460.1707; found: 460.1709.

4-(4-Chlorophenyl)-6-methyl-2,2-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3g). White solid (195 mg, 82%); mp 218–219 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.21 (dd, J = 8.2, 1.1 Hz, 1H), 7.59–7.45 (m, 5H), 7.35–7.19 (m, 12H), 5.94 (s, 1H), 3.52 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.56, 156.71, 143.45, 139.86, 137.99, 134.74, 133.03, 131.52, 128.68, 128.22, 127.94, 127.85, 126.74, 126.33, 123.57, 121.91, 115.79, 114.05, 107.77, 84.32, 29.21. IR (KBr) ν 3059, 2933, 1648, 1556, 1489, 1401, 1114, 989, 755, 699 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₂ClNO₂ + H]⁺): 476.1412; found: 476.1410.

4-(4-Bromophenyl)-6-methyl-2,2-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3h). White solid (193 mg, 74%); mp 177–178 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.22 (dd, J = 8.1, 1.4 Hz, 1H), 7.61–7.54 (m, 1H), 7.53–7.43 (m, 6H), 7.35–7.21 (m, 10H), 5.95 (s, 1H), 3.54 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.59, 156.75, 143.46, 139.90, 138.51, 134.79, 131.56, 130.80, 129.03, 128.25, 127.97, 126.77, 126.35, 123.61, 121.94, 121.29, 115.82, 114.10, 107.73, 84.35, 29.25. IR (KBr) ν 3062, 2937, 1736, 1648, 1557, 1486, 1400, 1114, 989, 760, 700 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₂BrNO₂ + H]⁺): 520.0907; found: 520.0904.

4-Cyclopropyl-6-methyl-2,2-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3i). White solid (118 mg, 58%); mp 213–214 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.14 (dd, J = 7.9, 0.7 Hz, 1H), 7.50 (t, J = 7.8 Hz, 1H), 7.44–7.36 (m, 4H), 7.32–7.17 (m, 8H), 5.62 (s, 1H), 3.61 (s, 3H), 2.81–2.56 (m, 1H), 0.98–0.77 (m, 2H), 0.75–0.47 (m, 2H); ¹³C NMR (100 MHz, CDCl₃) δ 160.73, 155.41, 144.21, 139.56, 136.91, 131.07, 128.08, 127.64, 126.74, 123.56, 121.71, 119.57, 115.78, 113.81, 109.18, 84.04, 29.10, 13.41, 7.34. IR (KBr) ν 3056, 3000, 1643, 1554, 1497, 1399, 1108, 990, 752, 701 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₈H₂₃NO₂ + H]⁺): 406.1802; found: 406.1801.

6-Methyl-4-phenyl-2,2-di-p-tolyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3j). Blue solid (193 mg, 82%); mp 236–237 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.19 (dd, J = 8.1, 1.5 Hz, 1H), 7.57–7.48 (m, 1H), 7.44–7.29 (m, 9H), 7.27–7.20 (m, 2H), 7.10 (d, J = 8.0 Hz, 4H), 5.92 (s, 1H), 3.52 (s, 3H), 2.29 (s, 6H); ¹³C NMR (100 MHz, CDCl₃) δ 159.66, 156.57, 140.90, 139.85, 139.68, 137.53, 135.42, 131.22, 128.81, 127.63, 127.32, 127.15, 126.77, 126.43, 123.58, 121.69, 116.00, 113.93, 108.12, 84.27, 29.20, 21.02. IR (KBr) ν 3032, 2932, 2838, 1733, 1649, 1555, 1461, 1385, 1113, 983, 757, 696 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₃H₂₇NO₂ + H]⁺): 470.2115; found: 470.2117.

2,2-Bis(4-methoxyphenyl)-6-methyl-4-phenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3k). White solid (108 mg, 43%); mp 218–219 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.17 (d, J = 7.9 Hz, 1H), 7.58–7.51 (m, 1H), 7.45–7.29 (m, 9H), 7.29–7.20 (m, 2H), 6.83 (d, J = 8.5 Hz, 4H), 5.89 (s, 1H), 3.76 (s, 6H), 3.54 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.70, 159.11, 156.56, 139.89, 139.68, 135.96, 135.42, 131.25, 128.29, 127.67, 127.33, 127.20, 126.49, 123.58, 121.71, 116.04, 113.98, 113.45, 108.12, 84.17, 55.21, 29.23. IR (KBr) ν 3056, 1652, 1556, 1489, 1393, 1116, 988, 757, 697 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₃H₂₇NO₄ + H]⁺): 502.2013; found: 502.2012.

2,2-Bis(4-chlorophenyl)-6-methyl-4-phenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3l). White solid (189 mg, 74%); mp 264–265 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.14 (dd, J = 7.9, 1.1 Hz, 1H), 7.62–7.52 (m, 1H), 7.48–7.39 (m, 4H), 7.39–7.32 (m, 5H), 7.31–7.22 (m, 6H), 5.85 (s, 1H), 3.55 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.44, 156.26, 141.72, 139.97, 139.06, 136.63, 134.10, 131.65, 128.52, 128.23, 127.78, 127.53, 127.25, 124.91, 123.35, 121.94, 115.62, 114.17, 108.35, 83.46, 29.29. IR (KBr) ν 3056, 1652, 1556, 1488, 1393, 1115, 988, 757, 697 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₁Cl₂NO₂ + H]⁺): 510.1022; found: 510.1024.

2-(4-Methoxyphenyl)-6-methyl-2,4-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3m). Yellow solid (141 mg, 60%); mp 253–254 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.19 (d, J = 8.3 Hz, 1H), 7.58–7.47 (m, 3H), 7.46–7.28 (m, 9H), 7.28–7.21 (m, 3H), 6.87–6.77 (m, 2H), 5.92 (s, 1H), 3.74 (s, 3H), 3.54 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.66, 159.20, 156.54, 144.04, 139.89, 139.61, 135.58, 135.56, 131.29, 128.43, 128.14, 127.70, 127.67, 127.32, 127.23, 126.69, 126.29, 123.56, 121.74, 115.98, 113.99, 113.48, 108.15, 84.24, 55.18, 29.23. IR (KBr) ν 3049, 2931, 2840, 1648, 1558, 1498, 1387, 1116, 989, 754, 699 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₂H₂₅NO₃ + H]⁺): 472.1907; found: 472.1904.

2-(4-Chlorophenyl)-6-methyl-2,4-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3n). Yellow solid (193 mg, 81%); mp 245–246 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.18 (d, J = 8.2 Hz, 1H), 7.60–7.53 (m, 1H), 7.52–7.42 (m, 4H), 7.41–7.21 (m, 12H), 5.91 (s, 1H), 3.54 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.54, 156.40, 143.27, 142.15, 139.94, 139.31, 136.20, 133.88, 131.50, 128.39, 128.37, 128.32, 128.04, 127.73, 127.40, 127.29, 126.69, 125.52, 123.46, 121.86, 115.78, 114.09, 108.28, 83.88, 29.27. IR (KBr) ν 3059, 2970, 1652, 1557, 1491, 1388, 1113, 986, 754, 697 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₂ClNO₂ + H]⁺): 476.1412; found: 476.1409.

2,2-Bis(4-methoxyphenyl)-6-methyl-4-(p-tolyl)-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3o). White solid (142 mg, 55%); mp 266–267 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.16 (dd, J = 8.0, 1.2 Hz, 1H), 7.61–7.50 (m, 1H), 7.47–7.34 (m, 4H), 7.32–7.21 (m, 4H), 7.20–7.11 (m, 2H), 6.89–6.74 (m, 4H), 5.87 (s, 1H), 3.76 (s, 6H), 3.55 (s, 3H), 2.36 (s, 3H); ¹³C NMR (101 MHz, CDCl₃) δ 159.72, 159.07, 156.53, 139.86, 136.76, 136.71, 136.00, 135.30, 131.18, 128.42, 128.29, 127.17, 126.09, 123.54, 121.68, 116.05, 113.95, 113.41, 108.21, 84.15, 55.19, 29.21, 21.28. IR (KBr) ν 2933, 2836, 1647, 1558, 1510, 1388, 1114, 989, 762, 717 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₄H₂₉NO₄ + H]⁺): 516.2169; found: 516.2166.

4-(4-Chlorophenyl)-2,2-bis(4-methoxyphenyl)-6-methyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3p). White solid (163 mg, 61%); mp 247–248 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.17 (dd, J = 8.0, 1.3 Hz, 1H), 7.61–7.52 (m, 1H), 7.43–7.36 (m, 4H), 7.34–7.26 (m, 5H), 7.26–7.21 (m, 1H), 6.89–6.78 (m, 4H), 5.87 (s, 1H), 3.76 (s, 6H), 3.55 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.66, 159.17, 156.74, 139.88, 138.13, 135.74, 134.43, 132.98, 131.44, 128.69, 128.23, 127.85, 126.72, 123.61, 121.85, 115.94, 114.04, 113.51, 107.70, 84.20, 55.21, 29.22. IR (KBr) ν 2934, 2836, 1732, 1644, 1558, 1491, 1387, 1115, 991, 759, 691 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₃H₂₆ClNO₄ + H]⁺): 536.1623; found: 536.1620.

6′-Methyl-4′-phenylspiro[fluorene-9,2′-pyrano[3,2-c]quinolin]-5′(6′H)-one (3q). Yellow solid (55 mg, 25%); mp 167–168 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.83 (dd, J = 8.0, 1.3 Hz, 1H), 7.66 (t, 4H), 7.56–7.48 (m, 1H), 7.42 (td, J = 7.5, 0.9 Hz, 2H), 7.37–7.17 (m, 8H), 7.07 (t, 1H), 5.56 (s, 1H), 3.68 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.84, 158.69, 146.49, 139.79, 139.68, 139.32, 136.35, 131.39, 130.21, 128.43, 127.57, 127.31, 127.11, 125.44, 124.09, 122.82, 121.57, 120.08, 115.80, 113.83, 106.93, 86.37, 29.39. IR (KBr) ν 3046, 1641, 1553, 1497, 1384, 1116, 986, 752, 698 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₁NO₂ + H]⁺): 440.1645; found: 440.1648.

4′-(4-Methoxyphenyl)-6′-methylspiro[fluorene-9,2′-pyrano[3,2-c]quinolin]-5′(6′H)-one (3r). Yellow solid (129 mg, 55%); mp 130–131 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.82 (dd, J = 8.0, 1.3 Hz, 1H), 7.65 (t, 4H), 7.55–7.46 (m, 1H), 7.41 (td, J = 7.5, 0.8 Hz, 2H), 7.31 (d, J = 8.5 Hz, 1H), 7.28–7.18 (m, 4H), 7.06 (t, J = 7.6 Hz, 1H), 6.92–6.81 (m, 2H), 5.53 (s, 1H), 3.80 (s, 3H), 3.68 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.87, 158.74, 158.72, 146.51, 139.63, 139.31, 135.91, 132.08, 131.33, 130.16, 128.42, 128.40, 125.43, 124.05, 122.07, 121.55, 120.04, 115.81, 113.79, 113.01, 107.00, 86.33, 55.12, 29.37. IR (KBr) ν 3940, 2930, 2833, 1734, 1646, 1556, 1511, 1383, 1114, 986, 754, 692 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₂H₂₃NO₃ + H]⁺): 470.1751; found: 470.1749.

4′-(4-Fluorophenyl)-6′-methylspiro[fluorene-9,2′-pyrano[3,2-c]quinolin]-5′(6′H)-one (3s). Yellow solid (85 mg, 37%); mp 134–135 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.83 (d, J = 7.9 Hz, 1H), 7.73–7.59 (m, 4H), 7.53 (t, J = 7.8 Hz, 1H), 7.42 (t, J = 7.5 Hz, 2H), 7.37–7.18 (m, 5H), 7.15–6.92 (m, 3H), 5.52 (s, 1H), 3.68 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.04 (d, J_C–F = 243.8 Hz), 159.85, 158.80, 146.40, 139.67, 139.32, 135.71 (d, J_C–F = 3.4 Hz), 135.42, 131.52, 130.28, 128.93 (d, J_C–F = 7.9 Hz), 128.46, 125.38, 124.12, 122.88, 121.68, 120.12, 115.74, 114.47 (d, J_C–F = 21.5 Hz), 113.87, 106.60, 86.36, 29.37; ¹⁹F NMR (377 MHz, CDCl₃) δ −115.47 (s). IR (KBr) ν 3042, 2925, 1645, 1556, 1508, 1384, 1115, 987, 754, 692 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₀FNO₂ + H]⁺): 458.1551; found: 458.1553.

4,6-Dimethyl-2,2-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3t). White solid (102 mg, 54%); mp 240–241 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.15 (dd, J = 7.9, 1.1 Hz, 1H), 7.55–7.49 (m, 1H), 7.48–7.41 (m, 4H), 7.33–7.27 (m, 4H), 7.27–7.20 (m, 4H), 5.75 (s, 1H), 3.60 (s, 3H), 2.45 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 161.05, 155.52, 144.31, 139.55, 131.08, 128.11, 127.65, 126.77, 123.58, 123.09, 121.76, 115.81, 113.82, 108.87, 84.12, 29.05, 20.99. IR (KBr) ν 3052, 2920, 1648, 1627, 1606, 1558, 1450, 1389, 1316, 1201, 984, 758, 701 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₃NO₂ + H]⁺): 380.1645; found: 380.1646.

4-Butyl-6-methyl-2,2-diphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3u). White solid (120 mg, 57%); mp 157–158 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.16 (dd, J = 7.9, 1.2 Hz, 1H), 7.55–7.48 (m, 1H), 7.47–7.40 (m, 4H), 7.33–7.31 (m, 1H), 7.30–7.29 (m, 2H), 7.28–7.27 (m, 1H), 7.27–7.19 (m, 4H), 5.77 (s, 1H), 3.60 (s, 3H), 2.92 (t, 2H), 1.57–1.48 (m, 2H), 1.46–1.35 (m, 2H), 0.92 (t, J = 7.2 Hz, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.67, 155.92, 144.33, 139.54, 135.50, 131.01, 128.09, 127.63, 126.83, 123.55, 122.70, 121.70, 115.91, 113.81, 108.61, 84.02, 33.20, 31.63, 29.16, 22.59, 14.11. IR (KBr) ν 3025, 2941, 1639, 1622, 1604, 1555, 1491, 1391, 1201, 1104, 955, 750, 700 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₉H₂₇NO₂ + H]⁺): 422.2115; found: 422.2114.

6-Methyl-2,2-diphenyl-4-(trimethylsilyl)-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3v). White solid (112 mg, 51%); mp 180–181 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.14 (d, J = 8.0 Hz, 1H), 7.50–7.40 (m, 5H), 7.33–7.26 (m, 4H), 7.26–7.17 (m, 4H), 6.29 (s, 1H), 3.58 (s, 3H), 0.32 (s, 9H); ¹³C NMR (100 MHz, CDCl₃) δ 161.44, 153.77, 144.05, 139.26, 135.00, 133.29, 130.76, 128.14, 127.65, 126.78, 123.25, 121.73, 116.08, 113.74, 111.17, 82.88, 29.36, 0.52. IR (KBr) ν 3058, 2952, 1643, 1618, 1591, 1492, 1384, 1126, 992, 751, 696 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₁H₂₃NO₂ + H]⁺): 438.1884; found: 438.1883.

2,2,4-Triphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3w). White solid (64 mg, 30%); mp 277–278 °C; ¹H NMR (400 MHz, CDCl₃) δ 12.29 (s, 1H), 8.07 (dd, J = 8.1, 1.0 Hz, 1H), 7.58–7.48 (m, 4H), 7.47–7.40 (m, 2H), 7.39–7.22 (m, 10H), 7.18 (t, J = 7.6 Hz, 1H), 6.67 (d, J = 8.2 Hz, 1H), 5.96 (s, 1H); ¹³C NMR (100 MHz, CDCl₃) δ 161.87, 158.47, 143.67, 139.42, 138.49, 135.20, 131.05, 128.21, 127.90, 127.79, 127.60, 126.87, 126.83, 125.61, 122.73, 122.04, 116.12, 114.94, 107.76, 84.55. IR (KBr) ν 3056, 2842, 1650, 1494, 1388, 1105, 950, 752, 695 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₀H₂₁NO₂ + H]⁺): 428.1645; found: 428.1647.

(Z)-6-(3-Hydroxy-1,3,3-triphenylprop-1-en-1-yl)-2,2,4-triphenyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3x). White solid (71 mg, 20%); mp 254–255 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.92 (dd, J = 7.9, 1.2 Hz, 1H), 7.66–7.60 (m, 2H), 7.55–7.45 (m, 4H), 7.45–7.38 (m, 5H), 7.38–7.30 (m, 5H), 7.30–7.28 (m, 2H), 7.27–7.26 (m, 1H), 7.26–7.20 (m, 4H), 7.20–7.13 (m, 4H), 7.12–7.04 (m, 3H), 6.78 (d, J = 8.3 Hz, 1H), 6.33 (t, J = 7.3 Hz, 1H), 6.17 (t, J = 7.7 Hz, 2H), 5.92 (s, 1H), 5.41 (s, 1H); ¹³C NMR (100 MHz, CDCl₃) δ 160.60, 157.77, 148.27, 144.26, 144.03, 143.69, 139.32, 137.86, 136.49, 136.41, 135.48, 135.02, 130.49, 128.84, 128.73, 128.43, 128.39, 128.22, 128.17, 127.71, 127.67, 127.48, 127.35, 127.21, 126.85, 126.66, 126.64, 125.77, 125.70, 125.57, 125.36, 124.88, 122.86, 122.30, 117.44, 115.56, 106.85, 84.81, 75.69. IR (KBr) ν 3057, 3027, 1735, 1637, 1600, 1553, 1492, 1393, 1163, 1011, 757, 696 cm⁻¹; HRMS (ESI): m/z calcd For ([C₅₁H₃₇NO₃ + H]⁺): 712.2846; found: 712.2843.

(Z)-6-(3-Hydroxy-3,3-diphenyl-1-(p-tolyl)prop-1-en-1-yl)-2,2-diphenyl-4-(p-tolyl)-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3y). White solid (203 mg, 55%); mp 166–167 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.91 (d, J = 7.9 Hz, 1H), 7.63 (d, J = 7.3 Hz, 2H), 7.56–7.36 (m, 7H), 7.35–7.22 (m, 8H), 7.21–7.11 (m, 4H), 7.11–6.96 (m, 7H), 6.76 (d, J = 8.4 Hz, 1H), 6.30 (t, J = 7.3 Hz, 1H), 6.13 (t, J = 7.7 Hz, 2H), 5.89 (s, 1H), 5.41 (s, 1H), 2.34 (s, 3H), 2.27 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.60, 157.70, 148.45, 144.44, 144.05, 143.79, 138.71, 137.90, 136.92, 136.42, 135.55, 135.45, 134.96, 133.59, 130.37, 129.51, 128.41, 128.36, 128.18, 128.12, 127.64, 127.31, 127.28, 126.78, 126.62, 125.81, 125.47, 125.27, 124.89, 122.78, 122.18, 117.46, 115.53, 106.95, 84.79, 75.66, 21.26, 21.11. IR (KBr) ν 3058, 3025, 2921, 1745, 1634, 1601, 1555, 1492, 1448, 1391, 1149, 755, 698 cm⁻¹; HRMS (ESI): m/z calcd for ([C₅₃H₄₁NO₃ + H]⁺): 740.3159; found: 740.3161.

(Z)-6-(3-Hydroxy-1-phenyl-3,3-di-p-tolylprop-1-en-1-yl)-4-phenyl-2,2-di-p-tolyl-2,6-dihydro-5H-pyrano[3,2-c]quinolin-5-one (3z). White solid (307 mg, 80%); mp 257–258 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.87 (dd, J = 7.9, 1.3 Hz, 1H), 7.54 (d, J = 8.2 Hz, 2H), 7.47–7.37 (m, 5H), 7.36–7.25 (m, 7H), 7.22 (s, 5H), 7.16–7.00 (m, 6H), 6.90 (d, J = 8.1 Hz, 2H), 6.68 (d, J = 8.3 Hz, 1H), 5.92 (d, J = 8.0 Hz, 2H), 5.83 (s, 1H), 5.32 (s, 1H), 2.38 (s, 3H), 2.32 (s, 3H), 2.26 (s, 3H), 1.72 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.72, 157.73, 145.67, 141.72, 141.27, 141.02, 139.48, 138.19, 137.70, 137.31, 136.67, 136.32, 136.29, 135.61, 134.79, 134.71, 130.23, 129.20, 128.86, 128.79, 128.68, 127.60, 127.57, 127.44, 127.37, 127.24, 126.52, 125.72, 125.65, 125.34, 124.70, 122.58, 121.98, 117.38, 115.60, 106.56, 84.91, 75.29, 21.15, 21.04, 20.95, 20.50. IR (KBr) ν 3023, 2920, 1738, 1633, 1604, 1551, 1493, 1387, 1149, 925, 749, 699 cm⁻¹; HRMS (ESI): m/z calcd for([C₅₅H₄₅NO₃ + H]⁺): 768.3472; found: 768.3473.

(Z)-2-Benzylidene-5-methyl-3-phenyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4a). White solid (110 mg, 60%); mp 210–211 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.00 (dd, J = 7.9, 1.4 Hz, 1H), 7.75–7.56 (m, 3H), 7.46–7.29 (m, 8H), 7.29–7.18 (m, 2H), 5.64 (d, J = 2.2 Hz, 1H), 5.36 (d, J = 2.2 Hz, 1H), 3.64 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.30, 159.60, 158.73, 140.91, 140.66, 134.48, 131.56, 128.73, 128.45, 128.33, 128.05, 127.35, 126.61, 123.17, 121.99, 114.73, 111.80, 111.39, 106.38, 51.20, 29.05. IR (KBr) ν 3059, 1694, 1658, 1641, 1568, 1494, 1404, 1121, 759, 700 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₉NO₂ + H]⁺): 366.1489; found: 366.1487.

(Z)-5-Methyl-2-(4-methylbenzylidene)-3-phenyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4b). White solid (80 mg, 42%); mp 201–202 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.98 (d, J = 7.8 Hz, 1H), 7.63 (t, J = 7.9 Hz, 1H), 7.56 (d, J = 8.0 Hz, 2H), 7.45–7.28 (m, 6H), 7.28–7.13 (m, 3H), 5.61 (s, 1H), 5.34 (s, 1H), 3.63 (s, 3H), 2.36 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.33, 159.63, 158.03, 140.92, 140.83, 136.38, 131.65, 131.49, 129.15, 128.69, 128.25, 128.06, 127.28, 123.18, 121.93, 114.70, 111.82, 111.46, 106.33, 51.12, 29.03, 21.21. IR (KBr) ν 3041, 2946, 1690, 1659, 1638, 1565, 1503, 1400, 1096, 751, 702 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₆H₂₁NO₂ + H]⁺): 380.1645; found: 380.1644.

(Z)-2-(4-Methoxybenzylidene)-5-methyl-3-phenyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4c). White solid (97 mg, 49%); mp 203–204 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.99 (d, J = 7.8 Hz, 1H), 7.71–7.54 (m, 3H), 7.45–7.29 (m, 6H), 7.28–7.19 (m, 1H), 6.92 (d, J = 8.4 Hz, 2H), 5.58 (s, 1H), 5.34 (s, 1H), 3.82 (s, 3H), 3.63 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.33, 159.66, 158.24, 157.11, 140.94, 140.92, 131.48, 129.58, 128.69, 128.05, 127.29, 127.26, 123.17, 121.91, 114.71, 113.90, 111.82, 111.48, 105.93, 55.24, 51.04, 29.03. IR (KBr) ν 3003, 2927, 2832, 2248, 1692, 1662, 1644, 1566, 1510, 1403, 1123, 757, 699 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₆H₂₁NO₃ + H]⁺): 396.1594; found: 396.1596.

(Z)-2-(2-Fluorobenzylidene)-5-methyl-3-phenyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4d). White solid (69 mg, 36%); mp 226–227 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.19 (t, J = 6.9 Hz, 1H), 7.97 (d, J = 7.8 Hz, 1H), 7.65 (t, J = 7.9 Hz, 1H), 7.48–7.30 (m, 6H), 7.29–7.14 (m, 3H), 7.03 (t, J = 9.3 Hz, 1H), 5.93 (s, 1H), 5.38 (s, 1H), 3.65 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.17, 160.07 (d, J_C–F = 2.1 Hz), 159.25 (d, J_C–F = 247.7 Hz),158.01, 140.98, 140.38, 131.62, 129.56 (d, J_C–F = 2.6 Hz), 128.80, 128.00 (d, J_C–F = 7.8 Hz), 127.98, 127.44, 124.01 (d, J_C–F = 3.6 Hz), 123.10, 122.41 (d, J_C–F = 12.0 Hz), 122.00, 115.16 (d, J_C–F = 22.1 Hz), 114.77, 111.94, 111.33, 97.58 (d, J_C–F = 7.7 Hz), 51.41, 29.08; ¹⁹F NMR (377 MHz, CDCl₃) δ −117.05 (s). IR (KBr) ν 3059, 3029, 2921, 1694, 1662, 1643, 1568, 1485, 1404, 1124, 750, 700 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₈FNO₂ + H]⁺): 384.1394; found: 384.1397.

(Z)-2-(3-Fluorobenzylidene)-5-methyl-3-phenyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4e). Yellow solid (98 mg, 51%); mp 211–212 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.99 (d, J = 7.8 Hz, 1H), 7.65 (t, J = 7.9 Hz, 1H), 7.51 (d, J = 10.3 Hz, 1H), 7.45–7.19 (m, 9H), 7.00–6.85 (m, 1H), 5.62 (s, 1H), 5.35 (s, 1H), 3.64 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.87 (d, J_C–F = 242.6 Hz), 160.15, 159.81, 159.48, 140.96, 140.33, 136.59 (d, J_C–F = 8.4 Hz), 131.67, 129.73 (d, J_C–F = 8.5 Hz), 128.81, 128.02, 127.47, 124.13 (d, J_C–F = 2.4 Hz), 123.13, 122.10, 114.97, 114.75, 113.41 (d, J_C–F = 21.4 Hz), 111.77, 111.26, 105.41 (d, J_C–F = 2.6 Hz), 51.34, 29.07; ¹⁹F NMR (377 MHz, CDCl₃) δ −113.17, −113.18 (m). IR (KBr) ν 3040, 1691, 1658, 1642, 1574, 1489, 1406, 1102, 755, 702 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₈FNO₂ + H]⁺): 384.1394; found: 384.1397.

(Z)-2-(4-Fluorobenzylidene)-5-methyl-3-phenyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4f). Yellow solid (77 mg, 40%); mp 221–222 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.98 (d, J = 7.8 Hz, 1H), 7.74–7.54 (m, 3H), 7.48–7.30 (m, 6H), 7.30–7.21 (m, 1H), 7.07 (t, J = 8.7 Hz, 2H), 5.60 (d, J = 2.1 Hz, 1H), 5.34 (d, J = 1.6 Hz, 1H), 3.64 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 161.31 (d, J_C–F = 245.0 Hz), 160.20, 159.55, 158.33 (d, J_C–F = 2.4 Hz), 140.90, 140.57, 131.61, 130.62 (d, J_C–F = 3.2 Hz), 129.88 (d, J_C–F = 7.8 Hz), 128.77, 127.99, 127.40, 123.08, 122.02, 115.33 (d, J_C–F = 21.4 Hz), 114.78, 111.78, 111.31, 105.25, 51.12, 29.07; ¹⁹F NMR (377 MHz, CDCl₃) δ −114.90 (m). IR (KBr) ν 3063, 2943, 1694, 1659, 1640, 1570, 1506, 1403, 1100, 753, 703 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₈FNO₂ + H]⁺): 384.1394; found: 384.1397.

(Z)-2-(4-Chlorobenzylidene)-5-methyl-3-phenyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4g). White solid (68 mg, 34%); mp 239–240 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.97 (dd, J = 7.9, 1.4 Hz, 1H), 7.70–7.63 (m, 1H), 7.62–7.55 (m, 2H), 7.44–7.30 (m, 8H), 7.30–7.23 (m, 1H), 5.59 (d, J = 2.2 Hz, 1H), 5.34 (d, J = 2.2 Hz, 1H), 3.65 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.15, 159.50, 159.22, 140.92, 140.39, 132.96, 132.04, 131.65, 129.50, 128.80, 128.56, 128.00, 127.45, 123.07, 122.05, 114.79, 111.77, 111.26, 105.22, 51.27, 29.08. IR (KBr) ν 3054, 2946, 1695, 1659, 1640, 1568, 1491, 1403, 1096, 753, 707 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₈ClNO₂ + H]⁺): 400.1099; found: 400.1096.

(Z)-2-Benzylidene-5-methyl-3-(p-tolyl)-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4h). White solid (68 mg, 36%); mp 214–215 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.99 (d, J = 7.8 Hz, 1H), 7.74–7.58 (m, 3H), 7.46–7.30 (m, 4H), 7.29–7.18 (m, 3H), 7.17–7.07 (m, 2H), 5.64 (d, J = 2.0 Hz, 1H), 5.32 (d, J = 1.7 Hz, 1H), 3.63 (s, 3H), 2.30 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.15, 159.60, 158.91, 140.83, 137.67, 136.92, 134.53, 131.47, 129.43, 128.41, 128.29, 127.91, 126.53, 123.12, 121.94, 114.70, 111.94, 111.39, 106.15, 50.84, 29.02, 21.10. IR (KBr) ν 3052, 3024, 1694, 1663, 1645, 1568, 1459, 1401, 1120, 752, 693 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₆H₂₁NO₂ + H]⁺): 380.1645; found: 380.1644.

(Z)-2-Benzylidene-3-(4-methoxyphenyl)-5-methyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4i). White solid (105 mg, 53%); mp 222–223 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.00 (dd, J = 7.9, 1.4 Hz, 1H), 7.73–7.59 (m, 3H), 7.43–7.27 (m, 6H), 7.26–7.19 (m, 1H), 6.91–6.82 (m, 2H), 5.64 (d, J = 2.2 Hz, 1H), 5.32 (d, J = 2.1 Hz, 1H), 3.77 (s, 3H), 3.64 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.05, 159.64, 159.00, 158.73, 140.84, 134.52, 132.78, 131.48, 129.09, 128.43, 128.29, 126.55, 123.13, 121.95, 114.71, 114.10, 111.95, 111.40, 106.15, 55.15, 50.47, 29.02. IR (KBr) ν 3001, 2949, 2831, 1694, 1662, 1644, 1566, 1494, 1403, 1121, 753, 692 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₆H₂₁NO₃ + H]⁺): 396.1594; found: 396.1596.

(Z)-2-Benzylidene-3-(4-fluorophenyl)-5-methyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4j). White solid (59 mg, 31%); mp 216–217 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.00 (d, J = 7.8 Hz, 1H), 7.74–7.58 (m, 3H), 7.50–7.30 (m, 6H), 7.29–7.16 (m, 1H), 7.01 (t, J = 8.6 Hz, 2H), 5.63 (s, 1H), 5.35 (s, 1H), 3.65 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.07 (d, J_C–F = 244.2 Hz), 160.31, 159.60, 158.51, 140.96, 136.46 (d, J_C–F = 3.3 Hz), 134.33, 131.68, 129.67 (d, J_C–F = 8.0 Hz), 128.50, 128.35, 126.76, 123.21, 122.07, 115.72, 115.51, 114.78, 111.47 (d, J_C–F = 24.2 Hz), 106.59, 50.47, 29.06; ¹⁹F NMR (377 MHz, CDCl₃) δ −115.30 (s). IR (KBr) ν 3036, 1694, 1662, 1643, 1570, 1507, 1403, 1122, 756, 693 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₈FNO₂ + H]⁺): 384.1394; found: 384.1397.

(Z)-2-Benzylidene-3-(4-chlorophenyl)-5-methyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4k). White solid (84 mg, 42%); mp 224–225 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.00 (d, J = 7.7 Hz, 1H), 7.67 (d, J = 7.4 Hz, 3H), 7.52–7.13 (m, 9H), 5.62 (s, 1H), 5.35 (s, 1H), 3.65 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.44, 159.57, 158.24, 141.00, 139.19, 134.27, 133.25, 131.76, 129.49, 128.94, 128.52, 128.38, 126.82, 123.25, 122.11, 114.82, 111.42, 111.34, 106.73, 50.62, 29.08. IR (KBr) ν 3023, 1693, 1662, 1641, 1567, 1493, 1403, 1121, 754, 692 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₈ClNO₂ + H]⁺): 400.1099; found: 400.1096.

(Z)-2-Benzylidene-3-(4-bromophenyl)-5-methyl-3,5-dihydrofuro[3,2-c]quinolin-4(2H)-one (4l). White solid (69 mg, 31%); mp 213–214 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.01 (d, J = 7.8 Hz, 1H), 7.67 (d, J = 7.4 Hz, 3H), 7.53–7.33 (m, 6H), 7.32–7.17 (m, 3H), 5.63 (s, 1H), 5.34 (s, 1H), 3.66 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 160.48, 159.58, 158.15, 141.02, 139.72, 134.26, 131.89, 131.78, 129.87, 128.53, 128.39, 126.84, 123.26, 122.13, 121.43, 114.83, 111.35, 106.77, 50.69, 29.09. IR (KBr) ν 3021, 1694, 1662, 1641, 1567, 1505, 1402, 1120, 753, 691 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₈BrNO₂ + H]⁺): 444.0594; found: 444.0597.

3-(1,3-Diphenylprop-2-yn-1-yl)-4-hydroxy-1-methylquinolin-2(1H)-one (5a). White solid (110 mg, 60%); mp 204–205 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.02 (dd, J = 8.0, 1.4 Hz, 1H), 7.88 (s, 1H), 7.68–7.46 (m, 5H), 7.40–7.29 (m, 6H), 7.28–7.19 (m, 2H), 6.11 (s, 1H), 3.73 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.39, 157.59, 139.33, 139.00, 131.79, 131.15, 128.83, 128.80, 128.42, 127.32, 127.14, 123.75, 121.82, 116.21, 113.80, 110.47, 87.45, 87.02, 33.07, 29.95. IR (KBr) ν 2940, 1637, 1556, 1489, 1393, 1248, 1152, 756, 693 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₉NO₂ + H]⁺): 366.1489; found: 366.1487.

4-Methyl-6,8,9,9-tetraphenyl-4,9-dihydro-5H-cyclopenta[lmn]phenanthridin-5-one (6a). White solid (158 mg, 60%); mp 287–288 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.57–7.52 (m, 2H), 7.50–7.35 (m, 4H), 7.26–6.97 (m, 16H), 6.85–6.76 (m, 2H), 3.70 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.11, 152.72, 145.35, 143.39, 142.80, 142.12, 141.35, 140.25, 139.31, 135.92, 134.82, 130.76, 129.46, 129.20, 128.50, 127.85, 127.46, 127.34, 127.26, 127.23, 126.83, 123.31, 118.48, 117.99, 110.75, 69.17, 29.42. IR (KBr) ν 3024, 1648, 1591, 1490, 1268, 1123, 1012, 758, 702 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₉H₂₇NO + H]⁺): 526.2165; found: 526.2164.

4-Methyl-6,9,9-triphenyl-8-(p-tolyl)-4,9-dihydro-5H-cyclopenta[lmn]phenanthridin-5-one (6b). White solid (151 mg, 56%); mp 264–265 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.58–7.51 (m, 2H), 7.49–7.35 (m, 4H), 7.21–6.98 (m, 13H), 6.88 (d, J = 7.5 Hz, 2H), 6.75–6.65 (m, 2H), 3.69 (s, 3H), 2.29 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.12, 152.69, 145.39, 143.53, 142.75, 142.20, 141.35, 140.30, 136.93, 136.46, 135.89, 135.03, 130.68, 129.45, 129.09, 128.54, 128.13, 127.83, 127.31, 127.22, 126.79, 123.33, 118.35, 117.98, 110.71, 69.16, 29.39, 21.11. IR (KBr) ν 3026, 1656, 1561, 1492, 1271, 1124, 960, 756, 707 cm⁻¹; HRMS (ESI): m/z calcd for ([C₄₀H₂₉NO + H]⁺): 540.2322; found: 540.2324.

8-(4-Methoxyphenyl)-4-methyl-6,9,9-triphenyl-4,9-dihydro-5H-cyclopenta[lmn]phenanthridin-5-one (6c). White solid (128 mg, 46%); mp 282–283 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.58–7.51 (m, 2H), 7.49–7.34 (m, 4H), 7.21–6.99 (m, 13H), 6.78–6.69 (m, 2H), 6.66–6.57 (m, 2H), 3.75 (s, 3H), 3.69 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.11, 158.88, 152.70, 145.53, 143.19, 142.77, 142.14, 141.37, 140.30, 135.88, 135.12, 131.81, 130.68, 130.40, 129.43, 128.52, 127.84, 127.31, 127.21, 126.82, 123.33, 118.30, 117.96, 112.89, 110.70, 69.13, 55.21, 29.38. IR (KBr) ν 3032, 1650, 1514, 1490, 1269, 1181, 1037, 752, 711 cm⁻¹; HRMS (ESI): m/z calcd for ([C₄₀H₂₉NO₂ + H]⁺): 556.2271; found: 556.2269.

9,9-Bis(4-methoxyphenyl)-4-methyl-6,8-diphenyl-4,9-dihydro-5H-cyclopenta[lmn]phenanthridin-5-one (6d). White solid (120 mg, 41%); mp 265–266 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.56–7.51 (m, 2H), 7.48–7.35 (m, 4H), 7.23–7.17 (m, 2H), 7.14–7.06 (m, 3H), 7.02 (d, J = 7.5 Hz, 1H), 6.94–6.88 (m, 4H), 6.87–6.82 (m, 2H), 6.66–6.57 (m, 4H), 3.73 (s, 6H), 3.69 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 162.13, 158.34, 153.19, 145.81, 143.21, 142.62, 141.19, 140.30, 139.42, 135.91, 134.76, 134.32, 130.71, 129.54, 129.44, 129.26, 127.46, 127.32, 127.22, 123.07, 118.42, 117.74, 113.15, 110.57, 67.90, 55.16, 29.39. IR (KBr) ν 3030, 2959, 1649, 1507, 1451, 1248, 1180, 1029, 758, 699 cm⁻¹; HRMS (ESI): m/z calcd for ([C₄₁H₃₁NO₃ + H]⁺): 586.2377; found: 586.2376.

9,9-Bis(4-chlorophenyl)-4-methyl-6,8-diphenyl-4,9-dihydro-5H-cyclopenta[lmn]phenanthridin-5-one (6e). White solid (140 mg, 47%); mp 314–315 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.58–7.36 (m, 6H), 7.28–7.19 (m, 2H), 7.18–7.09 (m, 3H), 7.09–7.02 (m, 4H), 6.97 (d, J = 7.5 Hz, 1H), 6.93–6.85 (m, 4H), 6.84–6.77 (m, 2H), 3.70 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 161.92, 151.73, 144.39, 143.33, 143.28, 141.13, 140.40, 139.94, 138.93, 136.10, 134.80, 132.92, 130.97, 129.68, 129.40, 129.00, 128.10, 127.69, 127.57, 127.40, 127.38, 123.10, 118.63, 117.60, 111.16, 68.05, 29.45. IR (KBr) ν 3026, 1650, 1591, 1489, 1266, 1093, 1012, 753, 697 cm⁻¹; HRMS (ESI): m/z calcd for ([C₃₉H₂₅Cl₂NO + H]⁺): 594.1386; found: 594.1388.

2-Benzyl-5-methyl-3-phenylfuro[3,2-c]quinolin-4(5H)-one (7a). White solid (70 mg, 96%); mp 156–157 °C; ¹H NMR (400 MHz, CDCl₃) δ 8.01–7.93 (m, 1H), 7.59–7.41 (m, 5H), 7.41–7.34 (m, 2H), 7.34–7.19 (m, 6H), 4.17 (s, 2H), 3.72 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.17, 154.38, 152.22, 137.94, 137.76, 130.90, 130.21, 129.25, 128.63, 128.38, 127.95, 127.56, 126.61, 121.99, 121.83, 121.14, 114.76, 113.98, 112.83, 32.44, 29.09. IR (KBr) ν 3022, 2940, 1655, 1582, 1493, 1225, 1113, 980, 744, 701 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₉NO₂ + H]⁺): 366.1489; found: 366.1487.

2-(4-Methoxybenzyl)-5-methyl-3-phenylfuro[3,2-c]quinolin-4(5H)-one (7b). White solid (74 mg, 94%); mp 141–142 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.97 (dd, J = 7.9, 1.3 Hz, 1H), 7.59–7.34 (m, 7H), 7.29–7.22 (m, 1H), 7.20–7.13 (m, 2H), 6.89–6.80 (m, 2H), 4.10 (s, 2H), 3.77 (s, 3H), 3.72 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.19, 158.31, 154.32, 152.67, 137.92, 130.95, 130.22, 129.78, 129.36, 129.22, 127.93, 127.52, 121.98, 121.50, 121.14, 114.76, 114.02, 113.99, 112.86, 55.21, 31.58, 29.09. IR (KBr) ν 3052, 2991, 1658, 1512, 1251, 1179, 1111, 1039, 746, 700 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₆H₂₁NO₃ + H]⁺): 396.1594; found: 396.1596.

2-(4-Chlorobenzyl)-5-methyl-3-phenylfuro[3,2-c]quinolin-4(5H)-one (7c). White solid (76 mg, 95%); mp 151–152 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.97 (dd, J = 7.8, 1.2 Hz, 1H), 7.57–7.49 (m, 3H), 7.48–7.35 (m, 4H), 7.31–7.23 (m, 3H), 7.20–7.13 (m, 2H), 4.13 (s, 2H), 3.73 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.13, 154.48, 151.61, 138.02, 136.19, 132.50, 130.73, 130.15, 129.72, 129.40, 128.76, 128.02, 127.69, 122.07, 121.14, 114.83, 113.98, 112.78, 31.85, 29.12. IR (KBr) ν 3035, 2895, 1653, 1581, 1489, 1308, 1220, 1111, 750, 699 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₅H₁₈ClNO₂ + H]⁺): 400.1099; found: 400.1096.

2-Benzyl-3-(4-methoxyphenyl)-5-methylfuro[3,2-c]quinolin-4(5H)-one (7d). White solid (73 mg, 92%); mp 172–173 °C; ¹H NMR (400 MHz, CDCl₃) δ 7.97 (dd, J = 7.9, 1.4 Hz, 1H), 7.53–7.44 (m, 3H), 7.39 (d, J = 8.5 Hz, 1H), 7.34–7.28 (m, 2H), 7.28–7.20 (m, 4H), 7.03–6.94 (m, 2H), 4.16 (s, 2H), 3.84 (s, 3H), 3.72 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 159.27, 159.08, 154.30, 151.89, 137.92, 137.88, 131.35, 129.18, 128.62, 128.36, 126.58, 123.11, 121.97, 121.46, 121.13, 114.75, 114.07, 113.50, 112.89, 55.23, 32.43, 29.07. IR (KBr) ν 3023, 2939, 1658, 1589, 1516, 1252, 1184, 1112, 752, 698 cm⁻¹; HRMS (ESI): m/z calcd for ([C₂₆H₂₁NO₃ + H]⁺): 396.1594; found: 396.1596.

Author contributions

H. Y. conducted most of the synthetic experiments. X. G., Z. F., M.-F. W., D. F. and Z. C. conducted a part of the propargylic alcohols. S. W., Y. W. and M. W. directed the projects and wrote the manuscript. All of the authors approved the final version of the manuscript.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the Excellent Young Talents Fund Program of Higher Education Institutions of Anhui Province (Grant No. gxyq2019041), the Foundation of Key Laboratory of Antiinflammatory and Immune Medicine, Ministry of Education, Anhui Medical University (KFJJ-2021-15, KFJJ-2020-10), the Natural Science Foundation of Anhui Higher Education Institutions of China (KJ2020A0619, KJ2021A0842), the National Natural Science Foundation of China (21602157), the College Students' Innovation and Entrepreneurship Program of Anhui Province (S202110368092).

Notes and references

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Footnote

† Electronic supplementary information (ESI) available: Copies of ¹H and ¹³C NMR spectra for newly synthesized compounds, CIF for compounds 3a, 3z, 4g and 6a. CCDC 2160295, 2189110, 2160296 and 2168808. For ESI and crystallographic data in CIF or other electronic format see https://doi.org/10.1039/d2ra03416f

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