1,2-BN cyclohexene has been produced from 1,2-BN cyclohexane through the loss of H2 and characterized and identified using a pulsed-beam Fourier-transform microwave spectrometer. Microwave spectra were measured in the frequency range of 5.5–12.5GHz, providing accurate rotational constants and quadrupole coupling strengths. Results of high level calculations allowed clear assignment of the spectra to 1,2-BN cyclohexene. Heating the initial compound, 1,2-BN cyclohexane, to 60°C in a 1atm neon stream results in the loss of H2 and conversion to 1,2-BN cyclohexene and this appears to be the first characterization of this compound as the 1,2-BN cyclohexene monomer.