Update for oxidopyridinium cycloadditions and their synthetic applications: advances after Katritzky's pioneering studies

Abstract

Since the pioneering studies of the Katritzky group, the cycloaddition of 3-oxidopyridinium betaines has been continuously studied because (1) the multifaceted reactivity of 3-oxidopyridiniums has attracted attention from the viewpoint of physical chemistry, and (2) the production of nitrogen heterocycles with three-dimensional frameworks is crucial for natural product chemistry and pharmaceutical sciences. In this review, the development of oxidopyridinium cycloadditions is discussed. First, the results of the seminal investigations on oxidopyridinium cycloadditions are briefly presented. Subsequently, the follow-up research conducted since the pioneering studies of Katritzky and others is discussed.