Facile one-pot multicomponent synthesis of 1H-pyrazolo[3,4-b]quinolines using L-proline as a catalyst

[Figure not available: see fulltext.] An efficient protocol for the synthesis of a new series of 1H-pyrazolo[3,4-b]quinolines has been described. The target compounds have been synthesized by one-pot multicomponent reaction of aniline, aromatic aldehydes, and 5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one using L-proline as an organocatalyst. Structural diversity and high yields of products, broad scope of aromatic aldehydes, simple operation, and short reaction times have been demonstrated as the advantages of the developed synthetic approach.