Multicomponent Reaction for the Synthesis of 5,6-Dihydropyrrolo[2,1‑a]isoquinolines

A multicomponent reaction between isatin, tetrahydroisoquinoline, and terminal alkyne in the presence of benzoic acid for the synthesis of N-(substituted-2-(2-phenyl-5,6-dihydropyrrolo­[2,1-a]­isoquinolin-3-yl)­phenyl)-3,4-dihydroisoquinoline-2­(1H)-carboxamides is described. This three-component reaction proceeds via sequential formation of spirooxindole, generation of isocyanate functionality via cleavage of the C2–C3 bond in the isatin subunit of spirooxindole, and addition of the second molecule of tetrahydroisoquinoline to the isocyanate group to offer title compounds. Expansion of the protocol to four-component by including an additional primary amine affords 1-substituted-3-(2-(2-phenyl-5,6-dihydropyrrolo­[2,1-a]­isoquinolin-3-yl)­phenyl)­urea in low to moderate yields. However, the reaction of intermediate spirooxindole with tetrahydroisoquinoline or any primary or secondary amine produced the title compound in excellent yields.