Novel 5-(4-Substituted-phenyldiazenyl)-1,3,2λ⁴-oxazaborines and Their Rearrangement to 1,2,4,3λ⁴-Triazaborines

The reaction of substituted benzenediazonium tetraphenylborates with the β-enaminones derived from pentane-2,4-dione, 1-phenylbutane-1,3-dione, and 1,4-diphenylbutane-1,3-dione with a primary or secondary (N-methyl, N-phenyl) amino group in CH2Cl2 gives 5-(substituted-phenyldiazenyl)-2,2-diphenyl-4,6-disubstituted-1,3,2λ4-oxazaborines or 5-(substituted-phenyldiazenyl)-2,2-diphenyl-3,4,6-trisubstituted-1,3,2λ4-oxazaborines, respectively. The reaction intermediate of these compounds has been identified, and a mechanism for the reaction has been suggested. Substituted 1,3,2λ4-oxazaborines gradually rearrange into 1,2,4,3λ4-triazaborines at temperatures above 100 °C.