Mechanistic Insights on the Annulation of Difluorocarbene and Enaminones

Computational studies on all proposed possible mechanisms of the annulations of difluorocarbene and enaminones were carried out, providing comprehensive mechanistic insights into the annulations. The results suggest that the asynchronous concerted [4 + 1] cycloaddition is more favorable for the annulation of difluorocarbene and enaminones, leading to 2,2-difluoro-2,3-dihydrofuran-3-amine derivatives and hardly to 3,3-difluoro-2,3-dihydrofuran-2-amine derivatives, which were even documented to be obtained and should be minor products. The calculation results were further verified experimentally. The current studies provide a thorough understanding of the annulation of difluorocarbene and enaminones and correct an unreasonable reported result.