Regioselective opening of epoxy alcohols: mild chemo- and stereoselective preparation of iodohydrins and 1,2-diols
摘要:
Several 2,3-epoxy alcohols have been opened, at -60-degrees-C, with MgI2, leading to the corresponding 3-iodo 1,2-diols with a high level of regio- and chemoselectivity. The iodohydrins can be reduced "in situ", by means of nBu3SnH, to the corresponding 1,2-diols. The chemo-, regio-, and stereocontrol of the reaction makes the method of wide use. Furthermore, epoxy alcohol derivatives (acetyl, benzyl, or TBMS) still maintain a strong preference for C-3 attack of the nucleophile. The experimental data strongly suggest that a metal (Mg) centered chelate is formed throughout the reaction, which gives rise to the regioselective delivery of the iodide ion.
An Efficient Catalytic Asymmetric Epoxidation Method
作者:Zhi-Xian Wang、Yong Tu、Michael Frohn、Jian-Rong Zhang、Yian Shi
DOI:10.1021/ja972272g
日期:1997.11.1
This article describes a highly effective catalyticasymmetricepoxidation method for olefins using potassium peroxomonosulfate (Oxone, Dupont) as oxidant and a fructose-derived ketone (1) as catalyst. High enantioselectivies have been obtained for trans-disubstituted and trisubstituted olefins which can bear functional groups such as tributylsilyl ether, acetal, chloride, and ester. The enantiomeric
Reaction of 2,3-epoxy-1-ol methanesulfonates with diethylaluminum chloride or with the mixture of diethylaluminum chloride and diethylamine hydrobromide in dichloromethane gave rise to regioselectively the corresponding 3-chloro- and 3-bromo-1,2-diol 1-methanesulfonates, respectively, in excellent yields.