Transition‐Metal‐Free Annulation of Sulfonyl‐Derived 1,3‐Enynes: Simple and Efficient Construction of 2,4‐Disubstituted Thiophenes and Vinyl Sulfone‐Tethered 1,2,3‐NH‐Triazoles

Abstract

AbstractThiophenes and 1,2,3‐NH‐triazoles are important frameworks in pharmaceuticals and advanced functional materials. Vinyl sulfones are also blueprint motifs in medicinal chemistry, but hybrid analogues of 1,2,3‐NH‐triazole‐derived from vinyl sulfones still need to be explored. In this report, we present an efficient and transition‐metal‐free [4+1]‐thioannulation of sulfonyl‐tethered 1,3‐enynes with Na2S in the presence of Cs2CO3 to generate 2,4‐disubstituted thiophenes in good to high yields. We also established a formal [3+2]‐cycloaddition of 1,3‐sulfonylenynes with NaN3 under metal‐ and base‐free conditions to synthesize vinyl sulfone‐containing 1,2,3‐NH‐triazole derivatives in moderate to high yields. The scope of these protocols was successfully showcased with various types of 1,3‐enynes bearing sensitive functional groups and complex structural scaffolds. The desired products were readily obtained with good functional group tolerance and compatibility. Based on the existing results and control experiments, plausible mechanistic pathways are also presented.