ISSN:
0009-2940
Keywords:
Tetrazatetraborocanes
;
Boron-nitrogen ring compounds
;
[2 + 3] Cycloadditions
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Eight-Membered BN Rings (RBNR')4 from Four-Membered BN Rings (RBNtBu)2 by an Exchange NtBu/NR'Reactions of the four-membered BN ring compounds (RBNtBu)2 (1a - e: R = Me, Et, iPr, iBu, Pr) with azides R'N3 (R' = PhCH2, Pr, iBu, Ph) and with the nitrone PhHC=N(Me)=O are studied. The five-membered ring [=(Me)B=N(tBu)-N=N-(PhCH2)N=] (2a) is formed from the four-membered ring 1a and PhCH2N3 in the ratio 1:2. An exchange of NtBu for NR' with elimination of tBuN3 is observed, however, in the reaction of the ring compounds 1b -d with R'N3. Instead of four-membered BN rings, the six-membered BN ring (RBNR')3 (3a: R/R' = Et/PhCH2) and the eight-membered BN rings (RBNR')4 (4a -h: R/R' = iPr/PhCH2, iBu/PhCH2, iPr/Pr, iBu/Pr, iPr/iBu, iBu/iBu, Et/Ph, iBu/Ph) are formed, respectively. The NMR spectra reveal diastereotopic methylene protons (Et, Pr, iBu, PhCH2) and methyl groups (iPr, iBu) and thus elucidate the tub-like structure of the eight-membered rings. 3a and 4a crystallize in the space group P2,/c. The reaction of the four-membered rings 1c - e with the nitrone gives five-membered rings [=(R)B=N(tBu)=B(R)=N(Me) - O=] (5c - e). Both of the reactions of the four-membered rings with azides and with the nitrone can be rationalized in terms of a similar sequence of reaction steps.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19911241011
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