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.
Silyl substituted furans in the stereoselective Birch reduction
作者:Timothy J Donohoe、Jean-Baptiste Guillermin、Andrew A Calabrese、Daryl S Walter
DOI:10.1016/s0040-4039(01)01151-0
日期:2001.8
Chiral derivatives of 3-silyl-2-furoic acid were prepared and subjected to a Birch reductive alkylation reaction. It was found that the presence of a silicon atom, ortho to the chiral auxiliary, enabled the synthesis of dihydrofurans with high levels of stereoselectivity. We believe that the silicon group is essential in order to control the geometry of the enolate formed in the reduction regime. Remarkably
Partial reduction of 3-heteroatom substituted 2-furoic acids: the role of an ortho group in viability and stereoselectivity
作者:Timothy J. Donohoe、Andrew A. Calabrese、Jean-Baptiste Guillermin、Christopher. S. Frampton、Daryl Walter
DOI:10.1039/b203437a
日期:2002.7.26
The synthesis of 2-furoic acid derivatives containing both 3-methoxy and 3-TMS groups is described. Reductive alkylation proceeded well to give us access to a series of highly functionalised dihydrofurans with potential for further elaboration. Of the two groups tested at C-3, the TMS derivative was found to be the more useful and gave rise to high levels of stereoselectivity when attached to a furan