HETEROCYCLES RELATED TO 2,4-DIBORA 1,3-DIAZAROBENZENE

Abstract

The reaction of ortho-substituted arylamines oY-C₆H₄NH₂ (Y = H, Cl, Br, Me) with BX₃, (X = F, Cl, Br, I) was investigated. By suitable choice of Y and X, this reaction may be directed to obtain, in a quantitative way, a new kind of heterocycle I instead of the expected trimeric species (oYC₆H₄NBX)₃. The formation of I was found to be related to the bulk of Y substituent and to the nature of X, increasing in the order BCl₃ < BBr₃ < BI, whereas BF₃ (X = F), with a tertiary amine added, always gives the corresponding borazines. Some derivatives of I were prepared (X = Me, Y = Br, Me) and characterized by NMR (¹H, ¹³C and ¹¹B) and mass spectra.

In connection with this study, we were led to the question of atropisomerism in the N-triarylborazines (oYC₆H₄NBX)₃ when the starting arylamine bears an ortho substituent Y. As far as the compound Y = Me, X = Me is concerned, a sole isomer, the C₃₀ one, could be obtained instead of the two expected.