N-doped TiO2 nanotubes catalyzed solvent-free domino strategy for the synthesis of α-keto triazoles

The present work describes the catalytic activity of nitrogen-doped TiO2 nanotubes (NTNTs) for solvent-free domino synthesis of a series of α-ketotriazoles from methyl ketones, N,N-dimethylformamide dimethyl acetal (DMF-DMA) and tosyl azide. The reaction proceeds through the in situ enaminone formation from methyl ketones and DMF-DMA followed by reaction with tosyl azide via a 1,3-dipolar cycloaddition. To our delight, NTNTs exhibited high catalytic activity towards the solvent-free synthesis of α-ketotriazoles from methyl ketones, DMF-DMA and tosyl azide as compared to both commercially available TiO2 and TNTs. The present domino strategy has several advantages which include its large substrate scope, low NTNT-2 loading, shorter reaction times and high yields. Further, the obtained α-ketotriazoles does not require column purification and NTNT-2 is used again for 7 cycles without significant loss of activity.