ASYMMETRIC SYNTHESIS OF SULTAMS AND SULFONAMIDES VIA DIASTEREOSELECTIVE REDUCTION OF N-SULFONYLIMINES

The diastereoselective reduction of both cyclic and acyclic camphor sulfonylimines was investigated. With cyclic camphor sulfonylimines 1, reduction using NaBH4 in methanol afforded the corresponding camphorsultarns 2 in 92-95% yield as single diastereomers with the exception of Ic where debromination occurred prior to reduction. For the large scale preparation of camphorsultam la and its derivatives, important chiral auxiliaries in asymmetric synthesis, reduction with NaBH4 is the reagent of choice. Reduction of acyclic camphor sulfonylimines 7 to camphorsulfonamides 8 with the bulky reducing reagent, LiAl(OBu-i)(3)H afforded the highest de's (>90% de) and yields 90-95%.