About the structure of two isomeric pyrazoloquinolines

Several structures are possible for the pyrazoloquinolines, formed in the Skraup synthesis from 5- or 6-aminoindazole. By nmr spectroscopic examination in the presence of shift reagents it was possible to assign the correct structures for both products, i.e., the angular 1H-pyrazolo-[3,4-f]quinoline ( 4 ) and 3H-pyrazolo[4,3-f]quinoline ( 2 ).