Tetramethylguanidinium triflate: An efficient catalyst solvent for the convergent synthesis of fused spiro[1,4-dihydropyridine-oxindole] compounds

Synthesis of spiro[1H-indeno[1,2-b]benzoquinolin-13,3′-indoline]-7,13-dihydro-12,2′-dione derivatives was achieved expediently through three-component reactions between 2H-indene-1,3-dione, 1- or 2-naphthalenamine, and isatin derivatives under catalysis of the ionic liquid N,N,N,N-tetramethylguanidinium triflate. The ionic liquid appeared as a task-specific catalyst solvent being amenable to successive recycling without appreciable decrease in activity. This synthetic method similarly works well when acenaphthylene-1,2-dione or 1H-indene-1,2,3-trione is employed in place of isatin and likewise when 2-aminouracil is used instead of naphthalenamine to furnish the structurally related spirocyclic products. A convergent mechanism was suggested for the reactions to account for the selective formation of the spiro-compounds corresponding to the employed components.