The reaction of phthalidylidene dichloride with primary amines. Synthesis and X-ray molecular structure of N-substituted phthalisoimides

An efficient method for the synthesis of N-substituted phthalisoimides, by reaction of phthalidylidene dichloride with primary amines, is described. The reactions with arylamines, arylenediamines and alkylenediamines lead to the corresponding phthalisoimides or bisphthalisoimides in nearly quantitative yields. However, the reactions with alkylamines are not useful because of the relatively high nucleophilicity of alkylamines. Certain particular behaviours of arylamines, associated with the presence of specific ortho-substituents have been found. The reactions of arylamines bearing an o-hydroxymethyl group provide a convenient method for preparing 2-benzoxazinylbenzoic acids. The X-ray crystallographic structures of N-(2-methoxyphenyl)phthalisoimide 3a and 2-(4H-3,1-benzoxazin-2-yl)benzoic acid 15a have been determined. (C) 1997 Elsevier Science Ltd.