Synthesis of α-Aryl Primary Amides from α-Silyl Nitriles and Aryl Sulfoxides through [3,3]-Sigmatropic Rearrangement.

A simple and efficient protocol was developed for the preparation of challenging α-aryl primary amides. This metal-free coupling process was triggered by TfOH-promoted electrophilic activation of α-silyl nitrile to generate keteniminium ion species, followed by reaction with aryl sulfoxide through [3,3]-sigmatrophic rearrangement to provide the target product. To the best of our knowledge, α-silyl nitrile has been rarely used as a pro-electrophilic reagent. Computational investigations confirmed the transient existence of a highly electrophilic keteniminium intermediate.