Unexpected Reactivity of Nitrones: Catalytic Insertion of CS.

A new reactivity mode for nitrones is reported, consisting of the chloride-catalyzed insertion of CS to afford thioamides. This reaction proceeds under metal-free and mild conditions, tolerates a broad family of substrates, and is robust and easily scalable, being successfully applied to the synthesis of the HIV-1 reverse transcriptase inhibitor UC-781. Mechanistic studies, supported by DFT calculations, have revealed the role of chloride anions in the activation of CS and its subsequent insertion into nitrones.