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Divergent Construction of Fully Substituted Pyrroles and Cyclopentadiene Derivatives by Ynamide Annulations: 1,2-Cyclopropyl Migration versus Proton Transfer.

Wenqing ZangYin WeiMin Shi
Published in: Organic letters (2020)
A switchable cyclopropyl ynamide cyclization to construct fully substituted pyrroles and cyclopentadiene derivatives in the presence of a gold catalyst was developed. In this version of pyrrole generation, a novel method to furnish gold vinylidenes through [1,2]-cyclopropyl migration was described. On the contrary, the production of cyclopentadienes proceeded through a proton-transfer step. These intriguing mechanisms were proposed based on the structure identification of the alkynyl enamine intermediate and a crossover experiment. The feasibility of cyclobutyl ynamides to specifically construct cyclopentadienes through ring expansion was also investigated.
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