K2S2O8-mediated radical cyclisation of 2-alkynylthioanisoles or -selenoanisoles: a green and regioselective route to 3-nitrobenzothiophenes and benzoselenophenes

Abstract

An acid, transition-metal, and chromatography-free radical nitration/cyclisation of 2-alkynylthioanisoles or -selenoanisoles has been developed. This is the first example of the use of highly unstable 2-nitrovinyl radicals for C-S bond formation. This facile route efficiently produces 3-nitrobenzothiophenes and benzoselenophenes, which are difficult to accessviaclassical methods. Density functional theory (DFT) calculations were carried out to probe the reaction mechanism. The resulting products were tested for theirin vitroanti-tuberculosis activity, and compounds2dand2lshowed significant activities against sensitive and drug-resistant strains.