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Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic Chemistry
Volume 40, 2010 - Issue 21
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Original Articles

Convenient Synthesis of 2,2-Dimethyl-3,4-dihydro-2H-pyrano[2,3-b]quinolines

, , &
Pages 3251-3258 | Received 30 Jul 2009, Published online: 04 Oct 2010
 

Abstract

A convenient general synthesis of 2,2-dimethyl-3,4-dihydro-2H-pyrano[2,3-b]quinolines using the Wittig reaction is described. The o-nitrobenzaldehydes (1a–d) on reaction with phosphorane 2 provided ( E )-ethyl-α-(2,2-dimethylprop-2-ene)-2-nitrocinnamates (3a–d) in excellent yields, which on cyclization with polyphosphoric acid followed by reductive cyclization using Fe/HCl afforded dihydropyranoquinolines (5a–d). Alternatively, the pyranoquinolines 5a–d were also synthesised from esters 3a–d by employing domino reductive cyclization in a single step.

ACKNOWLEDGMENTS

The authors thank the University Grants Commission, New Delhi, for financial assistance, the National Institute of Oceanography, Goa, for spectral analysis, and the Department of Organic Chemistry, IISC, Bangalore, for HRMS.

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