Transition-Metal Free Approaches to Access N-Heterocycles and Valuable Intermediates from Aryldiazonium Salts

Abstract

Efforts for the discovery of novel and efficient synthetic methods to achieve valuable N-fused heterocycles is an important research theme of organic chemistry for several decades. Owing to the importance of N-fused heterocycles in medicinal chemistry, material sciences, and organic synthesis, numerous efforts have been made to design robust methods for the construction of N-heterocyclic molecules. Aryldiazonium salts are privileged and readily accessible class of reagents/synthetic building blocks used in diverse ranges of disciplines in chemical sciences. Aryldiazonium salts based conventional C-C bond construction strategies are well established. On the other hand, due to its high electrophilic capacity, aryldiazonium salts have been broadly utilized in the efficient, atom-economic and rapid assembly of structurally unique nitrogen containing heterocycles via the formation of C-N bond in recent years. In this report, we review a diverse range of transition-metal free synthetic methodologies using aryldiazonium salts as key synthetic precursors to afford highly useful N-heterocyclic frameworks over the past nine years (2015 to date). In addition, application of these salts to prepare synthetically useful intermediates and precursors are also discussed. These N-heterocyclic motifs and intermediates are highly prevalent in varieties of natural products, agrochemicals and material applications.