Synthesis of (−)-(<i>S</i>,<i>S</i>)-clemastine by Invertive N → C Aryl Migration in a Lithiated Carbamate
作者:Anne M. Fournier、Robert A. Brown、William Farnaby、Hideki Miyatake-Ondozabal、Jonathan Clayden
DOI:10.1021/ol100627c
日期:2010.5.21
The first enantioselective synthesis of the antihistamineagent clemastine, as its (S,S)-stereoisomer, has been achieved by ether formation between a proline-derived chloroethylpyrrolidine and an enantiomerically enriched tertiary alcohol. The tertiary alcohol was formed from the carbamate derivative of α-methyl-p-chlorobenzyl alcohol by invertive aryl migration on lithiation. The (S,S)-stereochemistry
N to C Aryl Migration in Lithiated Carbamates: α-Arylation of Benzylic Alcohols
作者:Jonathan Clayden、William Farnaby、Damian M. Grainger、Ulrich Hennecke、Michele Mancinelli、Daniel J. Tetlow、Ian H. Hillier、Mark A. Vincent
DOI:10.1021/ja808959e
日期:2009.3.18
We report a new mode of reactivity displayed by lithiated O-benzyl carbamates carrying an N-aryl substituent: upon lithiation, the N-aryl group is transferred cleanly from N to C. An arylation of the carbamate results, providing a route to alpha,alpha-arylated secondary or tertiary alcohols. We also report density functional theory calculations supporting the proposal that arylation proceeds through a dearomatizing attack on the aromatic ring, a significantly lower energy pathway than the 1,2-acyl transfer observed with related N-alkyl carbamates.