Phosphine-Mediated Stereoselective Reductive Cyclopropanation of α-Substituted Allenoates with Aromatic Aldehydes

A novel phosphine-mediated reductive cyclopropanation between α-substituted allenoates 2 and aldehydes 1 is described. It represents a new member of the allene-based annulations, which provides facile and efficient access to highly functionalized cyclopropanes 3 from simple and readily available starting materials. It also unveils an unprecedented reactivity pattern of allenoates with aldehydes.