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.

Graphical abstractThe ionic liquid N,N,N,N-tetramethylguanidinium triflate was found an efficient catalyst solvent for promoting the synthesis of spiro[dihydropyridine-oxindole] compounds. This catalyst provided a quick method for sole production of the desired spiro-compounds from readily available and simple starting materials.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► TMGTf efficiently catalyzed the synthesis of spiro[1,4-dihydropyridine-oxindole]s. ► The synthesis is highly convergent without more care on reaction parameters. ► This method has a wide scope as examined by using variety of substrates. ► The catalyst is stable toward aqueous workup and easily was recovered several times.