Rhodium-Catalyzed Annulations of 1,3-Dienes and Salicylaldehydes/2-Hydroxybenzyl Alcohols Promoted by 2-Ethylacrolein

摘要

A rhodium-catalyzed 2-ethylacrolein-promoted protocol enables the annulation reactions of 1,3-dienes with either salicylaldehydes or 2-hydroxybenzyl alcohols leading to 2-alkylchroman-4-ones with high regioselectivity. This research highlights the use of 2-ethylacrolein which probably serves as a tool of bidentate coordination to rhodium intermediates. Mechanistic studies reveal that the transformation proceeds through the 1,4-hydroacylation pathway to access unsaturated linear ketones with subsequent oxo-Michael addition.