Species Containing One Boron Atom

4 Heterocycles Containing Three-Coordinate Annular Boron 4.2.2.4.1 Species Containing One Boron Atom 

The three-membered heterocycles of type 14 are obtained by treating fluoren-9-ylidene-(2,2,6,6-tetramethylpiperidin-1-yl)borane (containing a B=C double bond) with phenyl azide or trimethylsilanyl azide B and C NMR data are given [1]. The four-membered heterocycle 15 is prepared in a [2-1-2] cycloaddition from 2,2,6,6-tetramethylpiperidin-1-ylamino-f-butylimino-borane and tetracyanoethene [2]. 

HB[-N(CH3)CH2CH2N(CH3H- The reaction with pyrazole, C3H3N2H, has been studied by CNDO calculations. It was shown that the formation of [-N(CH3)CH2CH2N(CH3)-]B(N2C3H3) with elimination of H2 is exothermic with AE = -1.99 eV. The dimerization of the resultant pyrazolylborane is, however, energetically unfavorable (AE=+2.47 eV) [3]. 

The heterocycle 16 has been prepared by Diels-Alder addition of (CH3)3Si(f-C4H9)N-B= NC4H9-f to cyclopentadiene. Mass spectral and NMR data are reported [7]. 

The X-ray photoelectron spectra (XPS) of 2,3,5-triaryl-A -1,3,4,2-triazaborolines 17 have been studied. The three nitrogen atoms appear to be essentially equivalent. The derivatives studied are R = N02, R =Br, R3 = OCH3 and R = R =H, R = H, Br, CH3, OCH3, COOH, or 

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