Perimidines: a unique $\pi$-amphoteric heteroaromatic system

Data on the physicochemical characteristics, theoretical calculations, reactivity and synthetic methods for perimidines are summarized. Although perimidine and some of its simple 2-substituted derivatives were obtained by Sachs back in 1909, their chemistry and key physical properties remained unknown until the early 1970s. Subsequent studies revealed many fundamental features of the perimidine system, previously not encountered in the heterocyclic series. The first comprehensive review on perimidines was published forty years ago. The period that has passed since 1980 led to the emergence of new directions and trends. Several hundred new publications have appeared, the generalization of which has become the main purpose of this article. This primarily concerns the obtaining of highly nucleophilic and stable perimidine carbenes, new methods of electrophilic substitution and oxidation, establishment of a close relationship between perimidines and proton sponges, and modern theoretical calculations. Based on perimidines, many different polycondensed systems have been obtained. Applied research has developed especially rapidly in recent years. Many new compounds based on perimidines related to chemosensors, analytical reagents, dyes, metal catalysts, electronic devices, nanotechnology, and medical chemistry have been proposed. Some information under review is presented as Supplementary Materials. It contains six tables, which include data on the basicity constants of perimidines, details of some synthetic methods for perimidines and fused analogs and also a list of biological activities of perimidines. Bibliography — 379 references.