Synlett 2011(16): 2369-2373  
DOI: 10.1055/s-0030-1260312
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Palladium-Catalyzed One-Pot Synthesis of Pyrrole-Annulated Coumarin, Quinolone, and 7-Aza-indole Derivatives

K. C. Majumdar*a,b, Sintu Ganaia, Buddhadeb Chattopadhyaya, Krishanu Raya
a Department of Chemistry, University of Kalyani, Kalyani 741235, West Bengal, India
b Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784028, India
Fax: +91(33)25828282; e-Mail: kcm_ku@yahoo.co.in;
Further Information

Publication History

Received 9 June 2011
Publication Date:
13 September 2011 (online)

Abstract

An efficient one-pot approach for the synthesis of highly substituted pyrrolocoumarin, quinolone, and pyrrolopyridine derivatives has been achieved by palladium acetate catalyzed reaction in DMF through initially formed enamine from cyclic and acyclic ketones and 6-amino-5-bromocoumarin, 6-amino-5-bromo-1-methyl quinolone, and 2-amino-3,5-dibromopyridine, respectively.

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General Procedure for the Synthesis of Compound 3a by Heck Reaction A mixture of 1a (100 mg, 0.395 mmol), cyclohexanone (2a, 77.5 mg, 0.79 mmol), and DABCO (132.7 mg, 1.185 mmol) was taken in DMF (5 mL) under nitrogen atmosphere. Pd(OAc)2 (10 mol%, 8.8 mg) was added and the reaction mixture was stirred at 120 ˚C for 4 h. After completion of the reaction as monitored by TLC, the reaction mixture was cooled, H2O (20 mL) was added and extracted with EtOAc (3 × 30 mL). The EtOAc extract was washed with H2O (2 × 40 mL), followed by brine (30 mL). The organic layer was dried (Na2SO4), and the solvent was evaporated to give a crude product which was purified by column chromatog-raphy over silica gel (230-400 mesh) using PE-EtOAc (3:2) as eluent. Product 3a was isolated as a white solid in 91% yield. Compound 3a
Yield 91%, solid, mp 254-256 ˚C. IR (KBr): 1637, 3305 cm. ¹H NMR (400 MHz, CDCl3): δ = 8.30 (d, 1 H, J = 9.5 Hz), 8.00 (s, 1 H), 7.48 (d, 1 H, J = 9.0 Hz), 7.13 (d, 1 H, J = 9.0 Hz), 6.73 (d, 1 H, J = 9.5 Hz), 3.80 (s, 3 H), 3.00 (br s, 2 H), 2.80 (br s, 2 H), 1.93 (br s, 4 H). ¹³C NMR (100 MHz, DMSO): δ = 22.17, 23.13, 23.18, 23.41, 29.57, 107.28, 108.69, 112.51, 114.75, 118.38, 122.47, 130.57, 134.79, 135.60, 136.82, 160.65; MS: m/z = 253 [M+ + H]. Anal. Calcd for C16H16N2O: C, 76.16; H, 6.39; N, 11.10. Found: C, 76.34, H, 6.42, N, 11.27.