Development of biisoquinoline-based chiral diaminocarbene ligands: enantioselective SN2' allylic alkylation catalyzed by copper-carbene complexes

J Org Chem. 2008 Mar 7;73(5):1983-6. doi: 10.1021/jo702512z. Epub 2008 Feb 12.

Abstract

Chiral biisoquinoline-based diaminocarbene ligands (BIQ) were designed to create a chiral environment extended toward the metal center, which was confirmed by an X-ray structure. The concise ligand synthesis is highlighted by a modified Bischler-Napieralski cyclization of bisamides prepared from readily available chiral phenethylamines, and allows easy variation of the stereodifferentiating groups. The cyclohexyl-BIQ-copper complex is an efficient catalyst for enantioselective SN2' allylic alkylation with Grignard reagents showing SN2' regioselectivity higher than 5:1 and enantioselectivity in the range of 68-77% ee.