Sustainable Synthetic Approaches for Nitrogen‐Containing Heterocyclic Salts

This chapter presents different sustainable synthetic approaches mainly for the preparation of five‐ and six‐membered nitrogen‐containing nonaromatic and aromatic heterocyclic salts. It includes aromatic N‐heterocycles in order to present an overview of the most promising and comparative sustainable strategies for converting neutral N‐heterocycles or derivatives into salts. The chapter discusses water and aqueous solution reactions, alternative solvents and processes, solvent‐free reactions, microwave approaches, and sonication reactions for each family. It focuses on the synthesis of five‐membered N‐heterocyclic salts containing one nitrogen atom, namely pyrrolidinium, indolium, isoindolium, indolizinium, and pyrrolium salts. Six‐membered N‐heterocycles containing one nitrogen atom include pyridine derivatives such as picoline and lutidine, as well as piperidine and quinoline, among many others. Meanwhile, piperazine, pyridazine, and pyrimidinium are examples of six‐memberedN‐heterocycles containing two nitrogen atoms that have been explored recently for the sustainable preparation of salts.