PRODUCTION OF N-SUBSTITUTED LACTAM

PROBLEM TO BE SOLVED: To produce a N-substituted lactam economically and advantageously in an industrial scale by a reaction of a specified lactam with an organic halogen compound in the presence of a specific catalyst and specific base without solvents. SOLUTION: This N-substituted lactam is produced by a reaction of a lactam the N site of which is not substituted, preferably a compound of formula I (R' is an aliphatic hydrocarbon), as a starting material, with an organic halogen compound, preferably octyl chloride, dodecyl bromide, etc., in the presence of a solid-liquid interphase mobile catalyst, preferably a tertiary ammonium salt of formula II (R -R are each an alkyl, aralky or a heterocyclic group formed by a combination of two or three of R -R with N; X is an anion), specifically tetrabutylammonium bromide, and a solid inorganic base, preferably sodium hydroxide. This reaction is preferably carried out while restricting the presence of water in the reaction mixture as far as possible.