Enantioselective phase-transfer catalysis: Synthesis of pyrazolines

Abstract

All paired up: Under catalytic phase-transfer conditions the formation of a chiral ion pair between quininium cation 1 and hydrazine anion 2 led to an enantioselective aza-Michael cyclocondensation domino reaction to furnish pyrazolines. A convenient one-pot protocol allowed exchange of the functional group (R1) on the nitrogen atom. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.