The enantioselective a-addition of deconjugated butenolides has rarely been exploited, in contrast to the wellstudied g-addition of deconjugated butenolides.I nt his study, an unprecedented asymmetric a-addition/transesterification of deconjugated butenolides with ortho-quinone methides generated in situ afforded as eries of functionalized 3,4-dihydrocoumarins containing two contiguous stereogenic centers with excellent diastereo-and enantioselectivity.D FT calculations suggested that the rarely observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic dienolate and the electrophilic ortho-quinone methide.Scheme 1. Regioselectivity in asymmetric additionr eactions of deconjugated butenolides.