Efficient Method for the Deprotection of tert-Butyldimethylsilyl Ethers with TiCl4−Lewis Base Complexes: Application to the Synthesis of 1β-Methylcarbapenems
journal contributionposted on 07.07.2006, 00:00 by Akira Iida, Hiroki Okazaki, Tomonori Misaki, Makoto Sunagawa, Akira Sasaki, Yoo Tanabe
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‘.