Synthesis of Pyrrolidones and Caprolactams by Ring Modification or Multi‐component Ring‐Forming Reaction

Abstract

This chapter begins by discussing Lactone‐to‐Lactam Conversion, which is the basis for the commercial manufacture of pyrrolidone and N‐methylpyrrolidone. Multi‐component reactions accomplish the synthesis of pyrrolidones more readily than that of caprolactams. The chapter describes the use of the Beckmann rearrangement, the Schmidt reaction, rearrangement of oxaziridines and rearrangement of a‐azidoketones to synthesize caprolactams and pyrrolidones. The Beckmann rearrangement is the acid‐catalyzed isomerization of an oxime to an amide. The chapter discusses the methods of generating pyrrolidones and caprolactams by partial reduction of cyclic imides or by oxidation of cyclic amines. In multi‐component reactions, two or more molecules come together, forming two or more new sigma bonds and generating a new lactam ring. More complicated versions involve the Ugi reaction. The Ugi reaction involves the condensation of an isocyanide, an aldehyde or ketone, a primary amine and a carboxylic acid to form, ultimately, a structure having two amide linkages, an N‐acyl α‐amino carboxamide.

A Photochemical Strategy for the Synthesis of Caprolactams via Dearomative Ring Expansion of Nitroarenes

“…Traditionally, caprolactams have been mostly prepared from readily available cyclohexanones by Beckmann or Schmidt rearrangement (Scheme 1B). 6,7 The Beckmann rearrangement requires converting the ketone functionality into an oxime, followed by acid-catalyzed ring expansion (generally H 2 SO 4 ). In the Schmidt rearrangement, a nucleophilic azide reagent reacts with the ketone to promote, upon acidic treatment, a following migration to the desired caprolactam.…”