NEW METHODS FOR REDUCTIVE FREE-RADICAL CYCLIZATIONS OF ALPHA-BROMOACETALS TO 2-ALKOXYTETRAHYDROFURANS WITH ACTIVATED CHROMIUM(II)-ACETATE

被引：41

作者：

HACKMANN, C ^{[1
]}

SCHAFER, HJ ^{[1
]}

机构：

[1] UNIV MUNSTER,INST ORGAN CHEM,CORRENSSTR 40,W-4400 MUNSTER,GERMANY

来源：

TETRAHEDRON | 1993年 / 49卷 / 21期

关键词：

D O I：

10.1016/S0040-4020(01)81285-0

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

A method for the synthesis of gamma-butyrolactones 6 is described in which the key step is a free-radical cyclization of alpha-bromoacetals 4 to 2-alkoxytetrahydrofurans 5 in 54-93% yield induced by activated chromium(II)-acetate. Four new methods have been developed in order to activate the transition metal. Two of them require only catalytic amounts of chromium(II)-acetate, because it can be regenerated in situ chemically or electrochemically. The diastereoselectivity of the cyclization depends on the substitution pattern of 4 and ranges between 30.4:1 and 1:54.8.

引用

页码：4559 / 4574

页数：16

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