Flavan derivatives. XXII. 2'-Substituted flavanones and flavones; aroyl bromides by bromination of aromatic aldehydes

Abstract

Flavanone-2'-carboxylic acid, its methyl ester, and 2'-hydroxymethyl- flavanone were obtained from 3-o-hydroxyphenaoylphthalide. Bromination of the flavanones gave the corresponding cis-3-bromoflavanones which easily underwent base-catalysed dehydrobromination, and flavone-2'-carboxylic acid and its methyl ester were prepared in this way. Bromination of o-tolualdehyde gave o-toluoyl bromide in a known but hitherto neglected reaction which appears to offer a useful route to aroyl bromides.