Aromatic heterocycles 2: synthesis

Abstract

This chapter evaluates the synthesis of aromatic heterocycles. There are three major strategies in the synthesis of heterocycles: ring construction by ionic reactions; ring construction by cycloadditions; and modification of existing rings by electrophilic or nucleophilic aromatic substitution or by lithiation and reaction with electrophiles. The first strategy one should try out when faced with the synthesis of an aromatic heterocyclic ring is the disconnection of bonds between the heteroatom or atoms and carbon, with the idea of using the heteroatoms as nucleophiles and the carbon fragment as a double electrophile. The chapter looks at the Hantzsch pyridine synthesis and the Fischer indole synthesis. It also considers quinolines and isoquinolines.