Synthesis 2009(5): 793-800  
DOI: 10.1055/s-0028-1083363
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Palladium-Catalyzed Intramolecular Biaryl Coupling: A Highly Efficient Avenue for Benzannulated Pyranoquinolines and Julolidine Derivatives

K. C. Majumdar*, Abu Taher, Pradip Debnath
Department of Chemistry, University of Kalyani, Kalyani 741235, India
Fax: +91(33)25828282; e-Mail: kcm_ku@yahoo.co.in;
Further Information

Publication History

Received 6 October 2008
Publication Date:
11 February 2009 (online)

Abstract

A new efficient route to the synthesis of benzannulated pyranoquinolines has been accomplished via palladium-catalyzed intramolecular aryl-aryl cross-coupling reactions. The coupling reactions proceeded smoothly under ligand-free conditions with the catalytic system Pd(OAc)2/Cs2CO3/TBAB in high yields. Halogen-reduced product was not obtained in optimum reaction conditions. Regioselective synthesis of 5,6-dihydro-4H,8H-pyrido[3,2,1-de]phenanthridine is also described. In the latter case, a pronounced effect of base (Ag2CO3) has been observed on the efficiency of the conversion.

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Ames obtained only 35% of the biaryl coupled product from 2-bromobenzyl phenyl ether along with the dehalogenated product (40%) by reaction with Pd(PPh3)2Cl2 in DMA at 160 ˚C: Ref. 10.