Application of Walphos Ligand in the Pd(0)-Catalyzed Asymmetric Allylic Alkylation Reaction

Abstract

One relatively unexploited commercial ligand, Walphos 1, was tested in the Pd(0)-catalyzed asymmetric allylic alkylation using rac-1,3-diphenyl propenyl acetate and rac-1-acetoxycyclohexene as substrates, methyl malonate as nucleophile, and a variety of Pd precatalysts under standard conditions. The conversions and enantioselectivities were generally good, with the greatest substrate conversion of 99% and a greatest ee of 70%. With the latter cyclic substrate, an enantioselectivity of 98% was obtained, but the conversions were all poor (15–33%).

Keywords:

• Asymmetric allylic alkylation
• Pd(0)-catalyzed
• Walphos ligand

ACKNOWLEDGMENTS

We are grateful for the financial suport from Fundaça[otilde] para a Ciência e a Tecnologia (FCT) (Project POCI/QUI/55779/2004) through POCI 2010, supported by the European Community Fund, FEDER. FCT is also acknowledged for the award of a PhD grant to V. R. M. (SFRH/BD/25111/2005).

Notes

^a Reaction conditions: 2.5 mol% of ligand and precatalyst 1mol%, complexation occurred over a 2-h period, and then it was heated for 20 h (when base=BSA/KOAc, 1mol% KOAc was used).

^b See Experimental section for details.

^c Determined by HPLC using a Chiralcel OD-H column.

^a Reaction conditions: 2.5 mol% of ligand and precatalyst 1 mol% used, complexation occurred over a 2-h period, and it was kept at 40°C for 20 h (when base = BSA/KOAc, 1mol% KOAc was used).

^b Pertains to the ratio of substrate to product as determined by GC.

^c Determined by GC using a Cyclosyl-β column.