Enantioselective synthesis of threo-α,β-dihydroxyphosphonates by asymmetric dihydroxylation of 1(E)-alkenylphosphonates with AD-mix reagents
摘要:
Asymmetric dihydroxylation (AD) of 1(E)-alkenylphosphonates with an AD-mix -alpha or -beta reagent was examined to give a series of optically active threo-alpha,beta-dihydroxyphosphonates. Good enantioselectivity (>88% eel was observed in the AD reaction of 1(E)-alkenylphosphonates with conjugated aromatic substituents. The steric effects of the ester functionality in the course of the dihydroxylation were also evaluated. Enantioselectivity and yield were significantly improved when the AD reaction was carried out with dimethyl phosphonate instead of diethyl phosphonate. (C) 1997 Elsevier Science Ltd. All rights reserved.
Enantioselective synthesis of threo-α,β-dihydroxyphosphonates by asymmetric dihydroxylation of 1(E)-alkenylphosphonates with AD-mix reagents
摘要:
Asymmetric dihydroxylation (AD) of 1(E)-alkenylphosphonates with an AD-mix -alpha or -beta reagent was examined to give a series of optically active threo-alpha,beta-dihydroxyphosphonates. Good enantioselectivity (>88% eel was observed in the AD reaction of 1(E)-alkenylphosphonates with conjugated aromatic substituents. The steric effects of the ester functionality in the course of the dihydroxylation were also evaluated. Enantioselectivity and yield were significantly improved when the AD reaction was carried out with dimethyl phosphonate instead of diethyl phosphonate. (C) 1997 Elsevier Science Ltd. All rights reserved.
An efficient and novel method was developed towards the synthesis of alkenylphosphonates from simple olefins and phosphonate diesters. This method was enabled by the use of cheap and commercially available silver salts and TEMPO. This method exhibits of good functional group tolerance, specific (E)‐selectivity for all olefins and vinyl‐selectivity for aliphatic olefins. A radical mechanism was proposed
A base-free rhodium-catalyzed Mizoroki-Heck (M-H) reaction using potassium aryltrifluoroborates as the arylating agent of alkenes and acetone as a green '' oxidant '' is described. Thanks to the ready availability of organoboranes, this reaction should constitute an interesting alternative to conventional M-H reactions using aryl halides.
Chemoselective Hydrogenation of α,β-Unsaturated Sulfones and Phosphonates via Palladium-Assisted Hydrogen Transfer by Ammonium Formate
作者:Brindaban C. Ranu、Sankar K. Guchhait、Keya Ghosh