Regioselectivity and Stereospecificity in a Contrastereoelectronically Controlled Pinacol Rearrangement of Alkoxycyclobutane Derivatives. A Novel Route to Vicinally Substituted Cyclopentanones
作者:Debasis Patra、Subrata Ghosh
DOI:10.1021/jo00113a036
日期:1995.4
A four-step sequence for the synthesis of vicinally substituted cyclopentanones 5 and 9 has been developed starting from the acyclic ketones 1. The key step involves a stereospecific pinacol-type rearrangement of the cyclobutane ring embodied in oxabicyclo[3.2.0]-heptanes 4 and 8 involving exclusive migration of the stereoelectronically disfavored cyclobutane bond. The oxabicyclo[3.2.0]heptanes have been obtained by copper(I) triflate (CuOTf) catalyzed intramolecular photocycloaddition of the dienes 3 prepared from the ketones 1 on reaction with (ethoxyvinyl)lithium followed by allylation of the carbinols 2. The regioselectivity observed in bond migration has been attributed to be the result of the stabilization of the cation 15 by the neighboring hydroxyl group that is generated during the rearrangement.
A convenient route to vicinally substituted cyclopentanones via pinacol type rearrangement of cyclobutanes
作者:Subrata Ghosh、Debasis Patra
DOI:10.1016/0040-4039(93)88087-y
日期:1993.7
A convenient route to the vicinallysubstituted cyclopentanones 4,8 have been developed via rearrangement of oxabicyclo[3.2.0]heptanes obtained through intramolecular [2+2] photocycloaddition in dienes derived from ketones 1, 7.