Carboxylate-directed kumada coupling of an acetaldehyde synthon with 2-bromobenzoates used towards the synthesis of isochromanes

This letter describes the Kumada coupling of bromobenzoic acid derivatives with the acetaldehyde enolate synthon (1,3-dioxolan-2-ylinethyl)magnesium bromide. The lithium carboxylate salt shows the highest reactivity in the coupling reaction while addition of t-BuOLi affords optimal selectivity. During this work. we have observed a strong directing effect of the sodium carboxylate function which can be useful in differentiating electronically similar diaryl bromides.