Progress in Annulation Reactions Based on Huisgen Zwitterion

Abstract

The development of highly efficient and selective synthetic methodologies is an important research task in organic chemistry. In recent years, the Huisgen zwitterions, a type of intermediates derived from nucleophilic addition of tertiary phosphine to azodicarboxylates, have shown unique superiority and efficiency in synthesis of azacyclic compounds, and therefore have attracted broad interest from organic chemists. A large number of annulation reactions based on Huisgen zwitterions have been reported. According to the types of electrophiles, the annulation reactions of Husigen zwitterions with carbonyl compounds, electron-deficient alkenes, imines, and other electrophiles are summarized, respectively.

Synthesis of α-Amino Cyclobutanones via Formal 1,3-Hydroxy Migration Triggered by Formation of α-Imino Rhodium Carbene

“…α-Imino rhodium carbene, generated from 1-sulfonyl-1,2,3-triazole 1 , is usually employed as a 1,3-dipole to react with various unsaturated bonds giving different N-heterocycles . The reaction is usually initiated by nucleophilic attack on a carbene carbon producing a zwitterion, which is then transformed into various useful three- and five-membered compounds (Scheme A). , On the basis of the reaction mode mentioned above, organic chemists have developed a variety of methods for ring construction, making α-imino rhodium carbene one of the most important intermediates over the past decade. In addition, intramolecular group migration of functionalized carbene would convert it into a new zwitterion 2 .…”

Synthesis of Azepane Derivatives via Formal 1,3-Migration of Hydroxy and Acyloxy Groups and Selective Annulation

“…A zwitterion is a powerful synthetic intermediate in the construction of cyclic compounds via intra- or intermolecular annulation reactions . A controllable annulation from zwitterions with high regioselectivity between multiple reactive sites might be a flexible and convenient strategy for (hetero)­cycle formation, which is highly valuable in organic synthesis.…”