Creative approaches towards the synthesis of 2,5-dihydro- furans, thiophenes, and pyrroles. One method does not fit all!

Abstract

A single method is never sufficient, which is why there is a great need for developing many diverse and creative approaches towards every chemical substrate class. This statement is supported by the contents of this perspective in addition to providing the reader with a helpful synthetic roadmap for selecting a suitable method for the building blocks being discussed. Detailed in this review are eight different synthetic approaches that provide access to valuable 2,5-dihydro- furan, thiophene and pyrrole building blocks. Each approach is briefly presented and its limits discussed. The strengths and weaknesses of each approach are further highlighted with a graphical table summary at the end. This summary clearly drives home the point that for every chemical substrate class we need many good methods in order to provide access to every member of each class.

An Efficient, Overall [4+1] Cycloadditon of 1,3‐Dienes and Nitrene Precursors

“…Due to their important biological activities, a wide variety of methods have been developed to prepare these compounds, often with defined stereochemistry. [1] We are particularly interested in intermolecular cycloadditions for the construction of azacycles due to material convergence and catalytic control of the stereochemical outcome. Typical examples are [3+2] cycloadditions of olefins/alkynes with azomethine ylides [2] /aziridines [3] and [3+2] cycloadditions of imines with allenes, [4] trimethylenemethanes, [5] or cyclopropanes.…”

Azacycloalkanes from epoxides and aziridines

“…The rearrangement of vinylaziridine 168 in the presence of lithium iodide proceeds also under the microwave irradiation (Scheme 59) [169]. The obtained pyrrolidine derivatives proved to be a convenient intermediate in the synthesis of anisomycin [170].…”

Role of Microwaves in the Synthesis of Fused Five-Membered Heterocycles with Three N-Heteroatoms

“…[15][16][17][18] Consequently, the synthesis of fused five membered rings has posed a significantly greater challenge in comparison to the construction of their high membered or large ring counterparts. [19,20] In recent decades, a large number of reports related to synthesis of N,N,N-containing heterocycles have appeared owing to a wide variety of their biological activity. In recent years, numerous reports concerning the synthesis of heterocycles under solvent-free, reactants immobilized on solid support, microwave irradiation condition have appeared.…”