Synthetic studies towards xanthomonadin

Abstract

Synthetic studies aimed at the production of a natural dye, xanthomonadin 1, through the hydrobromination of a heptaene ester as a crucial step are described. The hydrobromination process using the CuO/4,7-(MeO)₂phen/[EMIM] catalyst system resulted in the formation of the bromo regioisomer, rather than the desired 1. However, the regioselectivity observed in the hydrobromination of polyenynic esters bearing different numbers of CC double bonds demonstrates the impact of electron push–pull effects.