Rhodium-Catalyzed Enamine Homologation of Sulfides with Triazoles as Carbene Precursor

We report on Rh(II)-catalyzed enamine homologation reactions of triazoles with cyclopropylmethyl sulfides. This reaction proceeds via Dimroth rearrangement of triazoles followed by rhodium-catalyzed ylide formation. This ylide, however, does not undergo classic rearrangement reactions. Instead, it undergoes a selective, intramolecular alkylation reaction to yield cyclopropylmethyl-substituted enamides. The application of this reaction was evaluated with different triazoles and sulfides, which underline the special reactivity of cyclopropylmethyl sulfides (29 examples, up to 83% yield).