Construction of 1,2-dihydro-1,3,5-triazines via reactions involving amidines.

1,2-Dihydro-1,3,5-triazine compounds were synthesized through three sets of reactions of amidines with, respectively, paraformaldehyde, aldehydes and N -arylnitrones under different conditions. The catalysts used in these three reactions were Cu(OAc) 2 , ZnI 2 and CuCl 2 ·2H 2 O, respectively. Most of the substrates tested for these reactions provided the target products in moderate to good yields. In the reactions involving paraformaldehyde, Cu(OAc) 2 also accelerated the release of formaldehyde from paraformaldehyde during the catalytic reaction process. In the case of the reactions involving nitrones, CuCl 2 ·2H 2 O not only catalyzed the normal progress of the main reaction, but also promoted the reaction of nitrones to produce nitroso compounds and aldehydes.