Studies of chromenes. Part 11. 3-Substitution of 7-methoxy-2,2-dimethylchroman-4-one without ring opening via 3-bromination
Abstract
3-Bromination of 7-methoxy-2,2-dimethylchroman-4-one 3a stabilises the anion 2a obtained on deprotonation with LDA sufficiently for 3-alkylation to take place without the usual ring-opening. Methylation in the presence of copper(I) bromide results in 3,3-dimethylation in good yield.