Asymmetric Traceless Petasis Borono‐Mannich Reactions of Enals: Reductive Transposition of Allylic Diazenes
作者:Yao Jiang、Regan J. Thomson、Scott E. Schaus
DOI:10.1002/anie.201708784
日期:2017.12.22
The traceless Petasis borono‐Mannich reaction of enals, sulfonylhydrazines, and allylboronates, catalyzed by chiral biphenols, results in an asymmetric reductivetransposition of the in situ generated allylic diazene. Acyclic 1,4‐diene products bearing either alkyl‐ or aryl‐substituted benzylic stereocenters are afforded in excellent yields and enantiomeric ratios of up to 99:1. The use of crotylboronates
Chiral dihydrobenzo[1,4]oxazines as catalysts for the asymmetric transfer-hydrogenation of α,β-unsaturated aldehydes
作者:Christian Ebner、Andreas Pfaltz
DOI:10.1016/j.tet.2011.10.051
日期:2011.12
A new class of organocatalysts based on the structure of 2,3-dihydrobenzo[1,4]oxazine was prepared and applied in the enantioselective transfer-hydrogenation of α,β-unsaturatedaldehydes with Hantzsch ester as hydride donor. These catalysts proved to be particularly effective for the conjugate reduction of β,β-diaryl-substituted acrylaldehydes leading to saturated aldehydes bearing a stereogenic center