Thiophenes and their saturated analogues are versatile C4-building blocks used to construct structurally intricate ring systems found in various biologically active structures. For instance, thiophenes can undergo dearomative cycloaddition reactions under photocatalytic conditions forming highly substituted benzenes. Thiophene S-oxides and S,S-dioxides have emerged as valuable precursors for the construction of complex frameworks in (4 + 2)/retro-(4 + 1) cascade reactions through cheletropic release of SO or SO2, respectively. In addition, 2,5-dihydrothiophenes can be rapidly converted into furans or pyrroles via pericyclic cascade reactions. The installation of a tetrahydrothiophene followed by reductive deletion of the sulfur atom has been demonstrated to be a powerful method for the cis-dialkylation of electron-poor olefins. The ability to generate highly complex, aromatic scaffolds and quaternary stereocenters makes thiophene compounds valuable intermediates for synthesizing natural products and bioactive molecules, which are important for crop science and medicinal chemistry. This minireview provides an overview of strategies for using these sulfur-containing heterocyclic precursors in challenging synthetic applications.
Keimer et al. (Mon,) studied this question.