Metal-free sulfenylation of pyrrolo[1,2-a]quinoxaline with diaryl disulfide facilitated by TBATB

A direct metal-free C1–H sulfenylation reaction of pyrrolo[1,2-a]quinoxaline with diaryl disulfides was developed at 50 °C using tetrabutylammonium tribromide (TBATB) as a promoter. Notably, raising the reaction temperature to 100 °C, TBATB played the dual role of both promoter and reactant, resulting in the simultaneous formation of C1–S bond and C3–Br bonds. The protocol has mild reaction conditions, broad substrate scope and good chemical and regioselectivity. In addition, the bifunctionalized reaction can be carried out smoothly at a gram-scale level, enabling the synthesis of structurally diverse pyrrolo[1,2-a]quinoxaline compounds.