Process for preparation of N-substituted maleimides
N-substituted maleimide represented by formula (2): STR1 is produced from N-substituted maleamic acid monoester represented by formula (1): STR2 in the presence of an acid catalyst by elmination of an alcohol from the monoester. The above N-substituted maleamic acid monoester represented by formula (1) is produced by esterification of N-substituted maleamic acid represented by formula (3): STR3 with an alcohol R2 -OH in the represence of an acid catalyst.