Construction of three contiguous tertiary stereocenters from aziridines in one step.

A range of active methylene nucleophiles were found to participate in ring-opening of tosylated aziridines under mild phase-transfer catalyzed conditions. High isolated yields coupled with a 1:1 reaction stoichiometry and high levels of relative stereocontrol are distinguishing features of this method. The products are obtained without epimerization, underscoring the optimal conditions afforded by the phase-transfer catalysis for connecting active methylene nucleophiles and weakly electrophilic N-tosylated aziridines.