Distinct Selectivity of 2-Aryl Thioquinazolinones in the Sulfur Directing Rh(III)-Catalyzed Amidation Reaction

Sulfur-directed C-H functionalization of N-heterocycles has emerged as an alternative solution to weakly coordinating carbonyl directing groups. In this study, we describe a sulfur-promoted Rh(III)-catalyzed C5 amidation of 4-thioquinazolinones using dioxazolones, yielding 5-amido-4-thioquinazolinones. The synthetic utility was demonstrated through a gram-scale experiment and synthetic modifications of the title compounds. A series of mechanistic investigations, including competition experiments, elucidated the effectiveness of the sulfur directing group in this process.