197248-09-2Relevant articles and documents
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
Norén, Rolf
, (2021/04/07)
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. The PIP group is orthogonal to the O-benzyl, O-acetyl, O-t-butyldiphenylsilyl, O-methyl, O-p-methoxybenzyl, O-allyl, O-tetrahydropyranyl and N-t-butoxy carbonyl groups. The CE step was systematically studied and was found to give higher yields when the reaction was performed in the presence of silylating agents.
Boron trichloride mediated regioselective Claisen rearrangement of resorcinol derivatives: Application to resorcinol carvonyl ethers
Ito, Fumihiro,Fusegi, Keiko,Kumamoto, Takuya,Ishikawa, Tsutomu
, p. 1785 - 1796 (2008/02/12)
Claisen rearrangement (CR) of resorcinol allyl ethers was examined. Although thermal CR gave low regioselectivity, the selectivity was much improved in the presence of a Lewis acid such as boron trichloride. This rearrangement was successfully applied to resorcinol carvonyl ethers for the regioselective introduction of a carvone unit into the resorcinol skeleton for the synthesis of phytoestrogenic miroestrols. Georg Thieme Verlag Stuttgart.
