Cyclization of 1-(4,4-diethoxybutyl)-3-arylureas: a case study

Reaction of nitrogen-containing acetals with aromatic compounds is a valuable method of synthesis of various heterocycles. Herein we report the study on the reaction of (4,4-diethoxybutyl)ureas with nucleophilic aromatics. We have found that the structure of the products mainly depends on the strength of the acid used as catalyst as well as aromatic nucleophile nature and its concentration. Either 2-arylpyrrolidines, diarylbutanes, bispyrrole derivatives, or pyrrolidinequinazolinones can be synthesized via variation of these factors. The proposed mechanism of the reaction is discussed.