Denitrogenation of tosylhydrazones: synthesis of aryl alkyl sulfones catalyzed by a phenalenyl-based molecule

Abstract

Sulfur-containing organic molecules such as sulfones are prevalent in pharmaceuticals and agrochemicals. Herein, we report the first transition-metal-free process for in situ denitrogenation of tosylhydrazones to produce a diverse array of aryl alkyl sulfones. We have used phenalenyl-based odd alternant hydrocarbon as a photoredox catalyst for denitrogenation of tosylhydrazones, where the phenalenyl acts as a potent oxidant to form a sulfinate radical intermediate from a sulfinate anion. We performed radical trapping, in situ electron paramagnetic resonance (EPR), and fluorescence quenching studies to elucidate the plausible mechanism. This method shows wide functional-group tolerance, with applications in late-stage modification of various natural products with good to high yields. The protocol provides an easy method for the synthesis of sulfones.