Stereoselective reduction of chiral 2-furoic acid derivatives using group I metals in ammonia
作者:Timothy J. Donohoe、Andrew A. Calabrese、Clare A. Stevenson、Tamara Ladduwahetty
DOI:10.1039/b006390h
日期:——
A series of chiral auxiliaries have been attached to 2-furoic acid and 3-methyl-2-furoic acid. The performance of these auxiliaries in the Birch reduction was assessed and it was found that placing a C-3 methyl group on the heterocycle was essential for good stereoselectivity. Using bis(methoxymethyl)pyrrolidine high levels of diastereoselectivity could be obtained with a range of electrophiles. A model is also presented which explains the sense of stereoselectivity displayed by this auxiliary. After reduction, the auxiliaries could be removed by reaction with acid to furnish dihydrofuran-based carboxylic acids with high enantiomeric excess.
一系列手性辅助试剂被连接到2-呋喃酸和3-甲基-2-呋喃酸上。这些辅助试剂在Birch还原中的表现进行了评估,结果发现,在杂环上放置一个C-3甲基基团对于良好的立体选择性至关重要。使用双(甲氧基甲基)吡咯烷,可以与多种电亲核试剂获得高水平的非对映选择性。还提出了一个模型来解释该辅助试剂所表现出的立体选择性的方向。在还原后,辅助试剂可以通过与酸反应去除,从而得到具有高对映体过剩的二氢呋喃基羧酸。