Access to Saturated Oxygen Heterocycles and Lactones via Electrochemical Sulfonylative Oxycyclization of Alkenes with Sulfonyl Hydrazides

Abstract

A facile electrochemical sulfonylative cycloetherification of linear unsaturated alcohols with sulfonyl hydrazides under mild conditions has been accomplished. This catalyst-and oxidant-free protocol proceeds via electro-oxidation, followed by radical addition, as well as an intramolecular oxygen nucleophilic process. This methodology is compatible with a broad substrate scope and good functional group compatibility, which provides a valuable and convenient synthetic tool for the synthesis of saturated five-, six-, seven-, and eight-membered ring oxygen heterocycles. Furthermore, sulfonylative cycloesterification of linear unsaturated acids toward the lactone products has also been established under this electrochemical system. In addition, control experiments indicated that the N−H bonds of the sulfonyl hydrazide molecule are non-essential.

N1-Allylation of Arylhydrazines via a Palladium-Catalyzed Allylic Substitution

“…Some challenges in regio- and chemoselectivity for both the arylhydrazines and allylic substrates could be met: (1) carbon–nitrogen bond cleavage of arylhydrazines, which resulted in a palladium-catalyzed Heck or analogous reaction; (2) selectivity of two nitrogen atoms on arylhydrazines as nucleophilic reaction sites; (3) selectivity of allylic substrates for the construction of branched or linear products . Recently, our group has been greatly interested in the dehydrazination couplings of monosubstituted hydrazines, and reported an electrochemical sulfonylative oxycyclization via dehydrazination of sulfonyl hydrazides and a palladium-catalyzed nonclassical Heck reaction via dehydrazination of arylhydrazines . Encouraged by Breit and Kwong and our previous works, we conjectured that the use of phosphine ligand would provide a satisfactory solution to the above challenges.…”

Electrochemical difunctionalization of alkenes and alkynes for the synthesis of organochalcogens involving C–S/Se bond formation

“…43 Recently, Zhang et al accomplished a facile electrochemical sulfonylative cycloetherification of linear unsaturated alcohols with sulfonyl hydrazides (Scheme 30). 44 This protocol features a broad substrate scope and good functional group compatibility, which provides a convenient synthetic tool for the synthesis of saturated five-, six-, seven-, and eight-membered ring oxygen heterocycles. Furthermore, sulfonylative cycloesterification of linear unsaturated acids toward the lactone products has also been established under this electrochemical system.…”

Electrochemical Radical Retro-Allylation of Homoallylic Alcohols with Sulfonyl Hydrazides

“…First, a single electrooxidation of aryl sulfonyl hydrazide (2) occurred at the anode and produced sulfonyl hydrazide radical cation A, which underwent a dehydrazination with the release of a proton, N 2 , and H 2 to give sulfonyl radical B. 20 Further addition of sulfonyl radical B to a homoallylic alcohol (1) afforded intermediate alkyl radical C. Subsequently, intermediate C underwent C−C bond cleavage, which produced the retro-allylation product and radical intermediate D. 18 Finally, radical intermediate D was oxidized to generate acetone at the anode, and protons were converted into H 2 via cathodic reduction.…”

“…In the past several decades, electrochemical organic synthesis has become a powerful tool for the construction of complex organic molecules via radical chemistry . Inspired by Studer’s works and our previous works, we report herein a novel electrochemical protocol of radical retro-allylation of homoallylic alcohols, exploiting a previously unrecognized opportunity in the field of C­(sp 3 )–C­(sp 3 ) bond cleavage (Scheme , eq 4). The method is characterized by employing sulfonyl hydrazides as environmentally friendly radical sources via electrochemical dehydrazination under metal- and base-free reaction conditions …”