Synthesis of fluorine containing N-benzyl-1,2,3-triazoles and N-methyl-pyrazoles from conjugated alkynes

1, 3-Dipolar-cycloaddition reaction of fluoro substituted 3-aryl-propynenitriles 1 with benzyl azide 2 afforded the expected 3-benzyl-5-aryl-3H-[1,2,3]triazole-4-carbonitrile 3 and 1-benzyl-5-aryl-1H-[1,2,3]-triazole-4-carbonitrile 4 in good yield. However, 1,3-dipolar cycloaddition of diazomethane 5 with 3-aryl-propynenitriles 1 resulted in the exclusive formation of N-methyl-pyrazole derivatives 6 and 7.

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