Eight-membered boron-nitrogen rings (RBNR')4 from four-membered boron-nitrogen rings (RBNBu-tert)2 by an NBu-tert/NR' exchange.
Reactions of diazadiboretidines I (R = Me, Et, Me2CH, Me2CHCH2, Pr) with azides and a nitrone are reported. Treating I (R = Me) with 2 equiv. PhCH2N3 in hexane gave 38% tetraazaborole II. Treating I (R = Et, Me2CH, Me2CH, Me2CHCH2) with R1N3 (R1 = PhCH2, Pr, Me2CHCH2, Ph) in hexane gave 43% III in one case; the rest of the time, eight-membered ring products IV (same R, R1) were formed. NMR spectral data indicate a tub-like structure for IV. Treating I (R = Me2CH, Me2CHCH2, Pr) with nitrone PhCH:N(Me)(O) gave 16-41% oxadiazadiborolidines V. The structure of III and IV (R = Me2CH, R1 = PhCH2) were detd. by x-ray crystallog.
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