A practical synthesis of a [2.2.1] bicyclic chiral sulfide for asymmetric transformations

A substantially improved synthesis of synthetically useful chiral sulfide 1 is described. Starting from (+)-10-camphorsulfonic acid, the chiral sulfide was synthesised on large scale in five steps and 56% overall yield. Significant improvements include the use of Bu3P in place of Ph3P for the reduction of the chlorosulfonyl group to the thiol, allowing removal of phosphine oxide by aqueous extraction and improvements in the photochemistry using either a modified batch reactor or a single pass continuous flow reactor. (c) 2006 Elsevier Ltd. All rights reserved.