Gold for the Generation and Control of Fluxional Barbaralyl Cations
作者:Paul R. McGonigal、Claudia de León、Yahui Wang、Anna Homs、César R. Solorio-Alvarado、Antonio M. Echavarren
DOI:10.1002/anie.201207682
日期:2012.12.21
comparison with the shape‐shifting barbaralylcation, which exists as a mixture of 181 400 degenerate forms. Gold‐catalyzed cycloisomerizations of 7‐alkynyl cyclohepta‐1,3,5‐trienes were found to proceed via fluxionalbarbaralyl intermediates (see scheme). The evolution of the intermediates into 1‐ or 2‐substituted indenes could be controlled by the choice of gold complex.
A new method has been developed for the preparation of 3-bromo-1-phenylallenes from 7-alkynylcycloheptatrienes and N-bromosuccinimide. Trisubstituted bromoallenes were obtained at room temperature in moderate to excellent yields. Functionalization of the carbon–bromine bond via Pd- or Cu-catalyzed cross-coupling reactions easily provided substituted allenes.