Lewis Base-Boryl Radicals Enabled the Desulfurizative Reduction and Annulation of Thioamides.

A new protocol for radical transformations of thioamides promoted by Lewis base-boryl radicals is reported. The desulfurizative reduction to access organic amines was enabled utilizing 4-dimethylaminopyridine-BH3 as the boryl radical precursor and PhSH as the polarity reversal catalyst. Alternatively, the chain process for unsaturated thioamides was switched to an annulation reaction using N-heterocyclic carbene-BH3 as the boryl radical precursor and sterically bulky Ph3CSH as the catalyst, allowing for the construction of N-heterocyclic and carbocyclic skeletons.