Asymmetric 1,4-Hydrosilylations of α,β-Unsaturated Esters

摘要

Ligands in the SEGPHOS and JOSIPHOS families of nonracemic bis-phosphines, when complexed with CuH, have been found to exert remarkably high degrees of facial selectivity in 1,4-reductions of β,β-disubstituted enoates. Levels of product ester ee's and chemical yields routinely in excess of 95% are observed employing high S/L ratios and are independent of substitution pattern in the substrate. These results suggest that this new technology is not only operationally straightforward but is also of considerable generality.