Synthetic studies towards xanthomonadin

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 CC double bonds demonstrates the impact of electron push-pull effects.