lower alkyl especially ethyl r 2 is hydrogen or lower alkyl especially hydrogen r 3 is hydrogen or lower alkyl especially methyl r 4 is hydrogen or lower alkyl especially hydrogen r 5 is lower alkyl especially methyl ethyl and isopentyl or di lower alkylaminolower alkylene especially dimethylaminopropyl and dimethylaminoethyl r 6 is lower alkyl or hydrogen especially hydrogen the products of the examples are representative of the various compounds of this invention and constitute especially preferred embodiments the new compounds of formula i are formed by the following series of reactions the symbols in the structural formulas have the same meaning as previously described a pyrazolo 3 4 b pyridine of the formula str4 produced according to the procedure given in u s pat no 3 761 487 sept 25 1973 is made to react with an iminonitrile of the formula str5 or a ketonitrile of formula str6 in an organic solvent like alcohol or the like by this reaction a hydrazone of the formula str7 is produced a compound of formula i wherein r 5 is hydrogen is now obtained by treating the compound of formula v in an organic acid like acetic acid with zinc chloride or any other lewis acid as catalyst alternatively the ring closure may be effected under basic conditions e g.