Abstract:

2-Bromo-2,3-dihydro-1H-1,3,2-diazaboroles I (R = CMe3, R1 = H; R = 2,6-Me2C6H3, R1 = H; R = Me3CCH2, R1 = Me) were synthesized by cyclocondensation reaction of the corresponding dilithiated RN:CR1CR1:NR with BBr3 in hexane. I (R = CMe3, R1 = H) was also obtained by Na/Hg redn. of the corresponding borolium salt in hexane. When this reaction was conducted in ether solvents, the diboroxane II resulted as the main product. I (R = CMe3, R1 = H) and the appropriate 1,3-dialkyl-4,5-dimethylimidazol-2-ylidenes underwent halide displacement to afford the borolylimidazolium salts III (R = Me, CHMe2). I-III were characterized by elemental anal. and spectroscopic methods. The mol. structures of II and III (R = Me) were established by single-crystal x-ray diffraction analyses.