Fehling solution/DIPEA/hydrazine: an alternative catalytic medium for regioselective synthesis of 1,4-disubstituted-1H-1,2,3-triazoles using azide-alkyne cycloaddition reaction

R = benzyl, substituted benzyl, phenyl, substituted phenyl, phenethyl R/ = -C6H5, 4-OMe-C6H4, 4-Me-C6H4.