Synthesis of Pyrrolidones and Caprolactams by Intramolecular Cyclization of Linear Precursors

Abstract

Pyrrolidones and caprolactams are important molecules, serving functions ranging from their use as solvents and surfactants to their occurrence in natural products and drugs. This chapter is devoted to the synthesis of pyrrolidones and caprolactams by intramolecular ring‐forming reactions. Perhaps the simplest heterolytic cyclization to envision is the attack of an amine group onto a carboxylic acid derivative, forming the amide C–N linkage. Pyrrolidones can be created by carboxamide radical cyclization onto an alkene. Amidyl radicals can activate remote C–H bonds to cyclization. The chapter presents the synthesis of pyrrolidones and caprolactams by homolytic (radical), carbene insertion and metathetic cyclization reactions. Carbenoid attack on an electron‐rich aromatic ring competes favorably with insertion into alkane C–H. Olefin metathesis is a metal‐catalyzed reaction that entails the redistribution of alkene carbons by the scission and regeneration of carbon–carbon double bonds.