Specificity of the reaction between carboryne and 3,6-diaryl-1,2,4,5-tetrazines

The possibility of the reactions of carboryne, a highly reactive organoboron analog of aryne, with 3,6-bis-substituted 1,2,4,5-tetrazines was studied. These reactions do not afford [4+2]-cycloaddition products. The reaction with 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine leads to N-carboranylation. In the case of 3,6-diphenyl-1,2,4,5-tetrazine, the sequential addition and rearrangement occur to give a dimeric product in 21% yield. The structures of the obtained organoboron compounds were confirmed by NMR spectroscopy, mass spectrometry, and X-ray diffraction analysis. The proposed mechanisms of the chemical transformations were additionally confirmed by the calculations. The results of this study are of interest for the targeted design of organoboron and hybrid materials as well as of potential agents for boron neutron capture therapy.