N-S bond cleavage of tosyl hydrazones by dual reactive arynes: synthesis of diaryl sulfones, spiro[indazole-3,3 '-indolin]-2 '-one, and N-phenyl sulfonohydrazides

A novel one-pot N-S bond cleavage of tosyl hydrazone derivatives of isatin and fluorenone by (het)arynes was discovered. The reaction produced diverse diaryl and heteroaryl-aryl sulfones as major products and diazomethyledenes of isatin/fluorenone or spiro[indazole-3,3 '-indolin]-2 '-one via [3+2]-dipolar cycloaddition reaction between diazomethyledenes of isatin/fluorenone and arynes, and N-phenyl benzenesulfonohydrazides via direct N-arylation by arynes. It has been established that the distribution of products depends on the nature of arynes and the source of fluoride ions and substrates. The structure of the products was established by spectroscopic and XRD methods. By invoking the dual reactivity of arynes as nucleophiles and electrophiles, two plausible reaction mechanisms for the formation of all the products are provided.