Pd-Catalyzed Asymmetric Cyclopropanation Reaction of Acyclic Amides with Allyl and Polyenyl Carbonates. Experimental and Computational Studies for the Origin of Cyclopropane Formation

Abstract

Cyclopropanes with three chiral centers were afforded in good to high yields with dr ratio of 4–23:1 and ee of 83–99% in the reaction of acyclic amides with monosubstituted allyl carbonates as well as polyenyl carbonates under the Pd-catalysis in the presence of (Sphos,R)-SIOCPhox L1 as the ligand, while allylic alkylated products were provided only if (Rphos,R)-SIOCPhox L2 was the ligand. The amide group of product was easily reduced to hydroxymethyl group in high yield. The active reaction intermediate was determined and transition states for cyclopropanation and allylation were calculated. The origin of cyclopropane formation was investigated by experiments, NMR studies, X-ray analysis of allyl-Pd-ligand complexes, and DFT calculations.