By-Product-Catalyzed Redox-Neutral Sulfenylation/Deiodination/Aromatization of Cyclic Alkenyl Iodides with Sulfonyl Hydrazides

A by-product-catalyzed redox-neutral process has been established through tandem sulfenylation/deiodination/aromatization of cyclic alkenyl iodides with sulfonyl hydrazides. In the absence of external catalysts and additives a range of 4-iodo-1,2-dihydronaphthalenes reacted with sulfonyl hydrazides to give structurally diverse 2-naphthyl thioethers in good yields. Mechanistic studies showed that at an early stage sulfonyl hydrazides decomposed completely to thiosulfonates and disulfides and at a late stage the resulting thiosulfonates underwent tandem sulfenylation/deiodination/aromatization with 4-iodo-1,2-dihydronaphthalenes involving a [1,5]-sigmatropic hydrogen shift. Importantly, iodine was generated as a by-product from 4-iodo-1,2-dihydronaphthalenes upon heating and served as a catalyst for the decomposition of sulfonyl hydrazides and subsequent formation of 2-naphthyl thioethers.