Efficient Baylis–Hillman reactions promoted by mild cooperative catalysts and their application to catalytic asymmetric synthesis

Baylis–Hillman reactions were promoted by mild cooperative catalysts of tributylphosphine with phenols such as (±)-1,1′-bi-2-naphthol (BINOL) in THF to give α-methylene-β-hydroxyalkanones in high yield. The reactions proceeded much faster in the presence of 1,1′-bi-2-naphthol than in its absence. The 1H NMR studies suggested that 1,1′-bi-2-naphthol functions as a Brønsted acid to activate the carbonyl group of an aldehyde and a polarized alkene. Application of the reactions to catalytic asymmetric synthesis was examined by using cooperative catalysts of tributylphosphine with the calcium chiral catalyst to give the desired product with fairly good % ee in fairly good yield.