Recent Contributions from the Baylis-Hillman Reaction to Organic Chemistry

There have been significant developments with respect to all the three essential components, namely activated alkenes or alkynes, electrophiles, and catalysts or catalytic systems. The acetates of the Baylis-Hillman alcohols derived from alkyl acrylate and aldehydes have been transformed into various poly-substituted phenol derivatives by Kim and coworkers via the alkylation using nitroalkanes, followed by Michael addition, cyclization, and aromatization strategies. Marko and co-workers have developed an interesting synthesis of bicyclic enedione, hydrindanones, and decalone derivatives from the Baylis-Hillman adducts obtained from cycloalkenones and terminal alkenals, following the reaction sequence shown in Schemes 291 and 292. Because of variations of parameters, flexibilities in using various combinations of activated alkenes, electrophiles, and catalysts, the understanding of the mechanism of this reaction has indeed become an intellectual puzzle.