Preparation of 3-Oxochroman and derivatives of 4'-Methoxyflav-2-ene (3-Cyano, 3-Formyl, and 3-Hydroxymethyl)

Abstract

3-Oxochroman was prepared by a known route from chrom-3-en-3-carboxylic acid, and 3-ethoxy-carbonyliminochroman and other intermediates were characterized. 3-Formyl-4?-methoxyflav-2-eneand 3-cyano-4?-methoxyflav- 2-ene were prepared in an attempt to obtain 4?-methoxyflav-2-en-3- carboxylic acid for conversion into 4?-methoxy-3-oxoflavan. However, the aldehyde proved resistant to oxidation, and the nitrile resisted hydrolysis, so that this route to 3-oxoflavans appeared unpromising. Reduction of 3-formyl-4?-methoxyflav-2-ene gave the acid-sensitive allylic alcohol, and 3-formyl-4?-methoxyflav-2-ene itself underwent acid-catalysed rearrangement to a mixture of cis- and trans-2-hydroxy- 3-(4-methoxybenzoyl)chroman.