Photochemical reactions of quinoid α-aryl-substituted γ-oxo-α,β-unsaturated carboxylic esters and amides. Formation of naphthacene and cycloheptatriene derivatives

✍ Scribed by W. Verboom; J. J. M. Brants; H. J. T. Bos

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 894 KB
• Volume: 101
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19821010203

✦ Synopsis

Abstract

Irradiation of the quinoid α‐aryl‐substituted γ‐oxo‐α,β‐unsaturated carboxylic esters 7a‐b and amides 10a‐b, derived from 9,10‐phenanthrenequinone, afforded, in addition to the Z/E isomers, the 8‐oxo‐8H‐benzo[f,g]naphthacene‐9‐carboxylic esters (13a‐b) and amides (15a‐b), respectively, by a dehydro‐cyclization of the stilbene system. Starting from the carboxylic ester 7c and amide 10d, with blocked ortho positions, cycloisomerization via an intramolecular (4 + 2)‐cycloaddition, with formation of the cycloheptatriene derivatives 16 and 17, was observed.

Irradiation of the α‐aryl‐substituted γ‐oxo‐α,β‐unsaturated carboxamides 12, derived from 3,5‐di__tert__‐butyl‐o‐benzoquinone, afforded, in addition to the Z/E isomers, the corresponding cycloheptatriene‐carboxamides 18. Starting from the carboxamide 12b,Φ = 0.074 ± 0.006 for the Z → E isomerization,Φ= 0.039 ± 0.004 for the E → Z isomerization and for the cycloisomerization Φ= 0.0016 ± 0.0006.