Synthesis 2012(8): 1268-1278  
DOI: 10.1055/s-0031-1290807
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of Cyclopentacarbazolones via Palladium-Catalyzed Annulation of Internal Alkynes

Devanga K. Sreenivas, Jatoth Sandhyarani, Rajagopal Nagarajan*
School of Chemistry, University of Hyderabad, Hyderabad 500046, India
Fax: +91(40)23012460; e-Mail: rnsc@uohyd.ernet.in;
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Publikationsverlauf

Received 8 December 2011
Publikationsdatum:
27. März 2012 (online)

Abstract

A simple and efficient protocol for the synthesis of highly substituted cyclopentacarbazolones (50-82%) was developed by employing internal alkynes with 2-bromo-3-formylcarbazoles in the presence of palladium catalyst under ligand-free condition. High regioselectivity was observed for unsymmetrical (alkyl-, aryl-­substituted) internal alkynes.

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X-ray crystallographic data for 3a: Formula: C30H23N1O1. Unit cell parameters: a = 9.0690(13), b = 10.359(2), c = 13.357(2), α = 85.794(15), β = 72.369(13), γ = 70.831(16), space group P1. X-ray crystallographic data for 3r: Formula: C26H23N1O1. Unit cell parameters: a = 8.3997(16), b = 10.227(2), c = 12.402(2), α = 76.514(3), β = 78.141(3), γ = 75.769(3), space group P1. X-ray crystallographic data for 3s: Formula: C25H21N1O1. Unit cell parameters: a = 7.9184(6), b = 10.4371(7), c = 12.1136(10), α = 76.338(6), β = 83.212(7), γ = 77.905(6), space group P1. The CCDC deposition numbers of compounds 3a,r,s are 840023, 840025, and 840024, respectively. Further data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(1223)336033, E-mail: deposit@ccdc.cam.ac.uk].