Chiral butenolides were synthesized by the enantioselective vinylogous Mannich reaction. Chiral (VAPOL)-type imidodiphosphoric acids are efficient catalysts for the asymmetric vinylogous Mannich (AVM) reaction of aldimines and trimethylsiloxyfuran in toluene. Under the optimized conditions, a series of butenolides were obtained with high yields (up to 98%) and enantioselectivities (up to 97% ee) as well as excellent diastereoselectivities (up to 99:1 dr).
Key words
butenolides - trimethylsiloxyfuran - organocatalysis - enantioselectivity - asymmetric vinylogous Mannich reaction