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

The three‐component reaction of the zwitterions generated from dialkyl acetylenedicarboxylates (=dialkyl but‐2‐ynedioates and triphenylphosphine (Ph 3 P) with isoindoline‐1,3‐diimine (=1 H ‐isoindole‐1,3(2 H )‐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 ).