Thermal Cycloadditions of Dimethyl Acetylenedicarboxylate to Cyclic Enol Ethers and Thioenol Ethers

Abstract

A new synthesis of substituted thiophenes is based on [2 + 3]‐cycloaddition of acetylenedicarboxylic esters to 2,3‐dihydrothiophenes. Transient yellow CT complexes lead to sulfonium ylides which in turn decompose to alkene and thiophene derivatives.

[2 + 2] Cycloaddition Reactions of 1-Trifluoroacetyl-2-chloroacetylene with Vinyl Ethers

“…Until now, however, only a few examples of such transformations have been reported in the literature, which mainly dealt with the reactions of acetylenedicarboxylate and propyolate esters [1][2][3]; chromium and tungsten ethynylcarbene complexes [4]; and, on extraordinary occasions, cyano-substituted acetylenes [5].…”

New Cascade Processes on Group 6 Fischer-Type Carbene Complexes: Cyclopropanation and Metathesis Reactions

“…At first, we employed the carbene complexes 1a and 1b , in an attempt to verify whether a possible, and predictable, tandem cycloaddition/cyclopropanation process might occur. Indeed, when typical procedures for [2+2] cycloadditions with alkynyl carbene complexes were used, homonaphthalenes 3a − d were formed in a diastereoselective way and were isolated with excellent yields (Table ).…”