New camphor-derived sulfur chiral controllers: Synthesis of (2R-exo)-10-methylthio-2-bornanethiol and (2R-exo)-2,10-bis(methylthio)bornane.

An efficient preparation of two camphor-derived controllers [(2R-exo)-10-methylthio-2-bornanethiol 1b and (2R-exo)-2,10-bis(methylthio)bornane 2] potentially useful as a ligands or chiral auxiliaries in asymmetric synthesis is described. Both compounds have been prepared starting from (1S)-camphor-10-thiol 3. Alkylation of this thiol with sodium methoxide and methyl iodide afforded 10-methylthiocamphor 8. Conversion of 8 into the corresponding thioketone 9 with the Lawesson's reagent followed by the stereoselective reduction with DIBAL-H at low temperature yielded (2R-exo)-10-methylthio-2-bornanethiol 1b in good yield. (2R-exo)-2,10-bis(Methylthio)bornane 2 could be obtained by alkylation of 1b with sodium methoxide and methyl iodide. Copyright (C) 1996 Elsevier Science Ltd.