Enantioselective [3 + 2]-Cycloadditions Catalyzed by a Protected, Multifunctional Phosphine-Containing α-Amino Acid

Catalytic asymmetric [3 + 2]-cycloaddition reactions between α-allenic esters and enones are presented. We have found that a simple phosphine-containing protected α-amino acid derivative is capable of promoting such cycloadditions in high yields with significant levels of regioselectivity and enantioselectivity. Furthermore, employing chiral racemic γ-substituted allenoates in the cycloaddition with chalcone substrates results in a “deracemization” reaction furnishing cyclopentenes in high yields with up to 93% ee.