Asymmetric Synthesis of Tertiary Thiols by Lithiation of Thiocarbamates

Abstract

Asymmetric Synthesis of Tertiary Thiols by Lithiation of ThiocarbamatesUniversity of ManchesterPaul MacLellanA submission for the degree of Doctor of Philosophy2010Tertiary thiols are a synthetically challenging class of compounds to prepare asymmetrically. The few reported methods for preparing these species require restrictive functionality to be incorporated into the products or are limited to employing simple carbon electrophiles.This thesis details investigations into the lithiation of N-aryl thiocarbamates. A stereoselective intramolecular arylation within lithiated thiocarbamates has been developed allowing the construction of quaternary stereocentres next to sulfur. Simple deprotection allows the isolation of enantiomerically pure tertiary thiols.A procedure for aryl migration within benzylic thiocarbamates has been developed and optimised. Rearrangement occurs in good yield and excellent stereoselectivity in a wide range of thiocarbamate substrates. Various substitution patterns are tolerated on the migrating aryl ring, the benzylic aryl ring and on the benzylic carbon centre.Extension of this methodology has incorporated an asymmetric alkylation of achiral benzylic thiocarbamates as a method of preparing aryl migration substrates. This allows the asymmetric synthesis of tertiary thiols in 2 steps from simple achiral precursors.Aryl migration has also been found to occur in lithiated allylic thiocarbamates with high stereospecificity, allowing preparation of a wider range of tertiary thiols.

Date of Award	31 Dec 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Jonathan Clayden (Supervisor)