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

Abstract

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 camphorsultams 2 in 92–95% yield as single diastereomers with the exception of 1c where debromination occurred prior to reduction. For the large scale preparation of camphorsultam 1a 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, LiAI(OBu-i)₃H afforded the highest de's (>90% de) and yields 90–95%.

Key Words:

• Asymmetric synthesis
• diastereoselective reduction
• chiral nonracemic sulfonamides
• sultans
• chiral auxiliaries