Metal-Free C–S Bond Formation in Elemental Sulfur and Cyclobutanol Derivatives: The Synthesis of Substituted Thiophenes

Abstract

A general approach for the metal-free synthesis of thiophenes by tert-cyclobutanols and elemental sulfur has been developed. This protocol provides a strategy for constructing multisubstituted thiophene derivatives via C−S bond formation under air. This reaction shows good functionality tolerance under the reaction conditions, and the mechanism is validated by control experiments and density functional theory calculations.

Ring‐Opening Functionalization/Cyclization Reactions of Cycloalkanols under Transition‐Metal‐Free Conditions

“…In 2022, the Yan group successfully prepared various functionalized thiophenes under metal‐free conditions via a ring‐expansion reaction of tert‐cyclobutanols with elemental sulfur (Scheme 28). [50] This strategy showed a board functional group tolerance, giving thiophenes in ideal yields. Radical trapping experiment excluded the possibility of radical pathway.…”

Photoredox-catalyzed cascade [2 + 2 + 1] cyclization of 1,6-enynes with thiols

“…Considering the above factors, the design and synthesis of sulfur-containing polycyclic compounds have attracted great interest in recent years. 3…”

Fe/S cluster catalyzed cascade cyclization of N,S-1,6-enynes for the synthesis of thieno[3,4-b]indoles

“…), which can be used as a reductant, 7 oxidant, 8 catalyst (activator), 9 or a building block in a reaction. 10…”