Synthesis,Crystal Structures and Quantum Chemical Calculations of 3,6-diphenyl-1,2-dihydro- and 1,4-dihydro-1,2,4,5-tetrazine derivatives

1-Acyl-3,6-diphenyl-1,4-dihydro-1,2,4,5-tetrazines were prepared by treatment of 3,6-diphenyl-1,4- (or 1,2)-dihydro-1,2,4,5-tetrazine and an equimolar amount of an acyl chloride. Further reaction with another equivalent of an acyl chloride yielded 1,4(or 1,2)-diacyl-3,6-diphenyl-1,4(or 1,2)-dihydro-1,2,4,5-tetrazines. Their structures are confirmed by ¹H NMR, IR, and mass spectra and by elemental analysis and X-ray diffraction. The experimental results are also validated by calculation of molecular stabilisation energies with the DFT calculations (B3LPY method). It can be shown that when alkanoyl chlorides are used, the products are the 1,4-dihydro-1,2,4,5-tetrazines, whereas acylation with aroyl chlorides affords 1,2-dihydro-1,2,4,5-tetrazines.