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

[GRAPHICS] 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 S(N)2' allylic alkylation with Grignard reagents showing S(N)2' regioselectivity higher than 5:1 and enantioselectivity in the range of 68-77% ee.