Mild and highly enantioselective vinylogous aldol reaction of brassards diene with aromatic aldehydes by combined lewis acid catalyst

摘要

(Figure presented) The combined Lewis acid catalytic system, generated from (R)-1,1′-bi-2-naphthol [(R)-BINOL], Ti(O-i-Pr)_4, H _2O, and lithium chloride, effectively catalyzed the enantioselective vinylogous aldol reaction of Brassards diene with aromatic aldehydes affording the (Z)-δ-hydroxyl-α,β-unsaturated esters exclusively in good yields with excellent enantioselectivities (90-99% ee) under mild conditions. A Lewis acid-Lewis acid bifunctional working model was proposed for the catalytic process based on some control experiments.