[3+3]-Cyclocondensation of β-Carbonyl-Substituted 4H-Chromenes with 3- and 6-Aminoindazoles: Synthesis of Pyrimido[1,2-b]indazoles and Pyrazolo[3,4-f]quinolines

A method for the synthesis of pyrazolo[3,4-f]quinolines from 6-aminoindazole and 4H-chromene-3-carbaldehydes or their fused analogs has been developed. It has been established that the reaction of β-trifluoroacetyl-substituted 4H-chromenes with 6-aminoindazole proceeds regioselectively to afford 9-trifluoromethylpyrazolo[3,4-f]quinolines. It has also been demonstrated that in reactions with 4H-chromene-3-carbaldehydes or 1H-benzo[f]chromene-2-carbaldehydes, 3-aminoindazoles act as 1,3-N,N-binucleophiles, thereby providing access to pyrimido[1,2-b]indazoles.