Substituted amidoximes when reacted with oxybis(diphenylborane) do not yield ester chelates as main products but boron heterocycles. The compound obtained from p-toluamidoxime was found by crystal structure analysis to be 2-phenyl-4-(4-methylphenyl)-2,3-dihydro-1,3,5,2-oxadiazaborol (9). The conformation of the molecule is determined by angles of 29.1 and 24.4° between the planes of adjacent rings. Except N–O all bonds in the heterocyclic ring contain significant π character. Molecules are linked to chains by a weak bifurcated hydrogen bond. 9 crystallizes with the monoclinic space group P21/c, Ζ = 4, a = 5.574(2), b = 18.274(4), c = 12.754(4) Å, β = 106.41(2)°. Refinement of 227 parameters using 1709 observed reflections converged at R = 0.037.