Synthesis of substituted imidazolines by an Ugi/Staudinger/aza-Wittig sequence

A series of 2-(acetamide-2-yl)-imidazolines (H) with 5 points of diversity were prepared by an Ugi-4CR-Staudinger-aza-Wittig-sequence starting from simple azidoalkylamines. The intramolecular aza-Wittig cyclization between the iminophosphane and the tertiary amide of the Ugi product (I) was effected by short microwave irradiation. Competitive cyclization to the secondary amide was not relevant, however, in some cases subsequent formation of the bicyclic ortho-amidines (III) was observed. (C) 2015 Elsevier Ltd. All rights reserved.