Chiral Epoxides via Borane Reduction of 2-Haloketones Catalyzed by Spiroborate Ester: Application to the Synthesis of Optically Pure 1,2-Hydroxy Ethers and 1,2-Azido Alcohols
作者:Kun Huang、Haiyang Wang、Viatcheslav Stepanenko、Melvin De Jesús、Carilyn Torruellas、Wildeliz Correa、Margarita Ortiz-Marciales
DOI:10.1021/jo102294j
日期:2011.3.18
with 10% spiroaminoborate ester 1 as catalyst is described. By a simple basic workup of 2-halohydrins, optically active epoxides are obtained in high yield and with excellent enantiopurity (up to 99% ee). Ring-opening of oxiranes with phenoxides or sodium azide is investigated under different reaction conditions affording nonracemic 1,2-hydroxy ethers and 1,2-azido alcohols with excellent enantioselectivity
Cyclometalated iridium complexes are shown to be highly efficient and chemoselectivecatalysts for the transferhydrogenation of a wide range of carbonyl groups with formic acid in water. Examples include α‐substituted ketones (α‐ether, α‐halo, α‐hydroxy, α‐amino, α‐nitrile or α‐ester), α‐keto esters, β‐keto esters and α,β‐unsaturated aldehydes. The reduction was carried out at substrate/catalyst ratios of