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Synlett 2008(6): 883-885  
DOI: 10.1055/s-2008-1042908
LETTER
© Georg Thieme Verlag Stuttgart · New York

Efficient Synthesis of Hantzsch Esters and Polyhydroquinoline Derivatives in Aqueous Micelles

Atul Kumar*, Ram Awatar Maurya
Medicinal and Process Chemistry Division, Central Drug Research Institute, Lucknow 226 001, India
e-Mail: dratulsax@gmail.com;
Further Information

Publication History

Received 13 June 2007
Publication Date:
11 March 2008 (online)

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Abstract

Hantzsch 1,4-dihydropyridine and polyhydroquinoline derivatives were synthesized in excellent yields in aqueous micelles. The reaction is catalyzed by PTSA and strongly accelerated by ultrasonic irradiation.

Key words

Hantzsch esters - polyhydroquinoline derivatives - aqueous micelles - PTSA

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Typical Experimental Procedure for the Synthesis of 1,4-Dihydropyridine Derivatives
In a 25 mL round-bottomed flask, benzaldehyde (1 mmol), ethyl acetoacetate (2 mmol), NH4OAc (1 mmol), and PTSA (0.1 mmol) was added. To this an aqueous solution of SDS (3 mL, 0.1 M) was added. The reaction mixture was immersed in an ultrasonic bath and irradiated for 1 h. Then, the reaction mixture was diluted with brine and extracted with EtOAc. The organic layer was dried over anhyd Na2SO4 and concentrated to give a crude product. The pure product was obtained by crystallization of the crude material from MeOH; mp 158 °C. 1H NMR (200 MHz, CDCl3): δ = 1.21 (t, J = 7.7 Hz, 6 H), 2.29 (s, 6 H), 4.08 (q, J = 7.7 Hz, 4 H), 4.98 (s, 1 H), 6.00 (s, 1 H), 7.01-7.26 (m, 5 H). IR (KBr): 3322, 1676, 1633 cm-1. MS: m/z = 330 [M + H]+. Anal. Calcd for C19H23NO4: C, 69.28, H, 7.04, N, 4.25. Found: C, 69.12, H, 6.98, N, 4.14.

9

Typical Experimental Procedure for the Synthesis of Polyhydroquinoline Derivatives
In a 25 mL round-bottomed flask, dimedone (1 mmol), benzaldehyde (1 mmol), ethyl acetoacetate (1 mmol), NH4OAc (1 mmol), and PTSA (0.1 mmol) was added. To this an aqueous solution of SDS (3 mL, 0.1 M) was added. The reaction mixture was immersed in an ultrasonic bath and irradiated until reaction was complete (TLC monitoring, 1-3 h). The reaction mixture was diluted with brine and extracted with EtOAc. The organic layer was dried over anhyd Na2SO4 and concentrated to give a crude product. The pure product was obtained by crystallization from MeOH; mp 203-204 °C. 1H NMR (300 MHz, CDCl3): δ = 0.94 (s, 3 H), 1.07 (s, 3 H), 1.21 (t, J = 7.1 Hz, 3 H), 2.13-2.29 (m, 4 H), 2.35 (s, 3 H), 4.06 (q, J = 7.1 Hz, 2 H), 5.07 (s, 1 H), 6.64 (s, 1 H), 7.08-7.13 (m, 1 H), 7.18-7.23 (m, 2 H), 7.28-7.33 (m, 2 H). 13C NMR (75 MHz, CDCl3): δ = 12.92, 17.96, 25.84, 28.15, 31.38, 35.33, 39.65, 49.50, 58.52, 104.72, 110.70, 124.74, 126.59, 126.72, 142.41, 145.82, 147.47, 166.24, 194.43. IR (KBr): 3287, 3078, 2963, 1697, 1611
cm-1. MS: m/z = 340 [M + H]+. Anal. Calcd for C21H25NO3: C, 74.31, H, 7.42, N, 4.13. Found: C, 74.27, H, 7.39, N, 4.08.