Synthesis of phenylacetaldehyde amidines and their intramolecular cyclization

The one-pot reaction of phenylacetaldehyde with a primary amine followed by tosyl azide yields the corresponding benzamidine 1 along with the N1-monosubstituted-N2-tosylformamidine 2. The participation of α-amino acid esters as reactants permitted the base-promoted intramolecular condensations of benzamidines 1d, 1e, 1f and 1i to give the corresponding 1,2-dihydropyrol-3- ones 6a-6d, respectively. The combination of phenylacetaldehyde, a pair of heterocyclic secondary amines, and 4-nitrophenyl azide in turn led to the two dihydrotriazole derivatives, 4b and 4c. Loss of nitrogen from 4 in refluxing toluene afforded trisubstituted benzamidines 5b and 5c, that also undergo base-promoted intramolecular condensation, forming 1,2-dihydropyrrol-3- ones 7a and 7b in turn