Synthesis of Tetrahydroindazole-Triazole Conjugates and their Derivatization by the Ritter Reaction

Abstract

7-Azido-3,6,6-trimethyl-1-(pyridin-2-yl)-1,5,6,7-tetrahydro-4H-indazol-4-one undergoes copper (I)-catalyzed 1,3-dipolar cycloaddition reactions with terminal alkynes and provides the corresponding 7-(1H-1,2,3-triazol-1-yl)-derivatives with excellent yields. Reduction of keto group at C(4) gives an access to diastereoisomeric mixture of alcohols. The latter provide acetamides in the Ritter reaction with acetonitrile upon treatment in acidic media. The developed synthetic sequence offers an easy entry into 4,7-difunctionalized tetrahydroindazoles which are interesting in terms of medicinal chemistry.