Straightforward access to oxazaborines, diazaborinones and triazaborines by reactions of β-enaminoamides with 4-methylbenzenediazonium tetraphenylborate

The reaction of substituted β-enaminoamides with 4-methylbenzenediazonium tetraphenylborate in dichloromethane produces besides the primary products of azo coupling reaction at the α-carbon atom of β-enaminoamides, also mixtures of heterocyclic compounds of boron: 1,3,2λ4-oxazaborines, 1H-1,3,2λ4-diazaborine-4-ones and 4H-1,2,4,3λ4-triazaborines. Proportions of the products change depending on the reaction conditions, particularly depending on the presence or absence of base (sodium acetate) in the reaction mixture. The heterocyclic compounds were separated chromatographically and identified by means of X-ray, 1H, 11B, 13C and 15N NMR spectra and elemental analyses.