Evaluation of 2-(piperidine-1-yl)-ethyl (PIP) as a protecting group for phenols: Stability to ortho-lithiation conditions and boiling concentrated hydrobromic acid, orthogonality with most common protecting group classes, and deprotection via Cope elimination or by mild Lewis acids
作者:Rolf Norén
DOI:10.1016/j.tet.2021.132108
日期:2021.5
A new protecting group, 2-(piperidine-1-yl)-ethyl (PIP), was evaluated as a protecting group for phenols. The PIP group was stable to ortho-lithiation conditions and refluxing with concentrated hydrobromic acid. Deprotection was accomplished by two routes, oxidation to N-oxides followed by Cope elimination (CE) and subsequent hydrolysis or ozonolysis of the vinyl ether or one-step deprotection by BBr3•Me2S
评价了新的保护基2-(哌啶-1-基)-乙基(PIP)作为酚的保护基。PIP基团在原锂化条件下稳定,并在浓氢溴酸中回流。脱保护可通过两种途径完成,即氧化为N-氧化物,然后进行Cope消除(CE),然后进行乙烯基醚的水解或臭氧分解,或通过BBr 3 •Me 2 S进行一步脱保护。PIP基团与O-正交。苄基,O-乙酰基,Ot-丁基二苯基甲硅烷基,O-甲基,Op-甲氧基苄基,O-烯丙基,O-四氢吡喃基和Nt-丁氧基羰基。对CE步骤进行了系统地研究,发现当在甲硅烷基化剂存在下进行反应时,可以提高收率。