Enantioselective Dialkylzinc Addition to Aldehydes Catalyzed by Chiral Zn(II)-BINOLates Bearing Phosphonates and Phosphoramides in the 3,3′-Positions

Abstract

Highly enantioselective dialkylzinc addition to a series of aldehydes was developed based on chiral Zn(II)-BINOLate catalysts bearing phosphonates [P(=O)(OR)₂] and phosphoramides [P(=O)(NMe₂)₂] at the 3,3′-positions. The reactions proceeded smoothly and showed reductions in the amounts of both catalysts and dialkylzinc reagents to be loaded.

Key words

aldehyde - asymmetric catalysis - C-C bond formation - dialkylzinc addition - phosphoryl group

References and Notes

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10

For hexanal in entry 13, 3 mol% of (R)-3 with 1.5 equiv of Et₂Zn was more reactive than 10 mol% of 3,3′-bis(diphenylphosphinoyl)-BINOL (71%) with 3 equiv of Et₂Zn in our previous report. See ref. 7.

11

Ligands 1-3 were stable under air and moisture conditions. We could easily recover these ligands from the reaction mixture by silica gel column chromatography.