Arylthiols as highly chemoselective and environmentally benign radical reducing agents

Arylthiols serve as excellent environmentally benign reducing agents for organotellurium, organostibine, and organobismuthine compounds under radical conditions. Both small molecules and macromolecules possessing these heteroatom groups are reduced under moderate thermal conditions to give near quantitative yields in most cases. The reduction shows high chemoselectivity with respect to the heteroatom compounds; the reactivity decreases in the order alkylbismuthines, alkylstibines, and alkyltellurides, while simple alkyl iodides could not be reduced. Alkyltellurides are selectively reduced in the presence of alkyl iodides even when an excess amount of arylthiol is used. Furthermore, alkylstibines are also selectively reduced in the presence of alkyltellurides. Moreover, the reduction conditions are compatible with the presence of a variety of polar functional groups in the substrates, products, and solvents, which are not tolerant under ionic and metal-catalyzed conditions. Carbon-carbon bond formation is possible with use of the carbon-centered radicals that are generated. The results clearly reveal the synthetic utility of arylthiols in organic synthesis.