Multicomponent Transformation of Isoindoline‐1,3‐diimine (=1H‐Isoindole‐1,3(2H)‐diimine), Acetylenic Esters, and Triphenylphosphine to Novel Dihydropyrimido[2,1‐a]isoindole Derivatives

Abstract

The three-component reaction of the zwitterions generated from dialkyl acetylenedicarboxylates (¼ dialkyl but-2-ynedioates and triphenylphosphine (Ph 3 P) with isoindoline-1,3-diimine (¼ 1H-isoindole-1,3(2H)-diimine) is described (Scheme 1). This reaction affords the corresponding special type of substituted dihydropyrimido[2,1-a]isoindole derivatives in good yields without using any catalyst and activation (Table).Introduction. -In recent years, the construction of the hydropyrimidine frameworks has been the subject of numerous investigations [1], since six-membered pyrimidine and fused pyrimidine heterocycles are ubiquitous structural components of several natural products with a wide range of biological activities [2 -5]. Among them, pyrimidoindoles and pyrimidoisoindoles are well known for their potential biological and pharmacological activities, especially antitumor [6], cytotoxic [7], and anti-HIV [8] activities. Due to the biological activity of fused pyrimidines and the little attention paid to the synthesis of pyrimidoisoindole derivatives [9] [10], we wish herein to report, in continuation of our recent investigations [11 -15], a simple and efficient method for the preparation of novel dihydropyrimido[2,1-a]isoindole derivatives.