Efficient method for the deprotection of tert-butyldimethylsilyl ethers with TiCl4-Lewis base complexes: Application to the synthesis of 1β-methylcarbapenems

Article abstract of DOI:10.1021/jo0604484

TiCl₄-Lewis base (AcOEt, CH₃NO₂) complexes smoothly deprotected tert-butyldimethylsilyl (TBDMS) ethers. The reaction velocity with these complexes, which seemed less reactive due to the influence of Lewis bases, was considerably greater than that with TiCl₄ alone. Selective desilylations between aliphatic and aromatic TBDMS ethers (1 and 5), between 1 and benzyl, allyl, tosyl, methoxyphenyl, and chloroacetyl ethers (13, 14, 15, 16, and 17), and between TBDMS and TBDPS ethers (18 and 19) were successfully performed. Desilylation of TBDMS-aldol, acyloin, and β-lactam analogues 9-12 proceeded smoothly due to anchimeric assistance by the neighboring carbonyl groups. The present method was successfully applied to the practical synthesis of 1β-methylcarbapenems 20a′-f′.