367941-18-2Relevant academic research and scientific papers
Reactions at the B-B Bond of Tri-tert-butylazaboriridine NB2R3: Ring Extensions
Luckert, S.,Eversheim, E.,Englert, U.,Wagner, T.,Paetzold, P.
, (2008/10/08)
The OCO carboxylate unit of pivalic acid adds to the B-B bond of the azadiboriridine NB2R3 (1a, R=tBu) to give the chiral heterocyclohexadiene 2a; the enantiomers of 2a are transformed into one another by a [1,3] sigmatropic hydride transfer along the B-N-B ring fragment. The azadiboracyclopentanes 3a-e are formed from 1a and the alkenes ethene, propene, isobutene, (trimethylsilyl)ethene, and 2,3-dimethyl-1-butene. Only one double bond of cyclopentadiene and 1,3-butadiene reacts in the same way to give 3f,g, respectively, and both of the double bonds of 1,3-butadiene react with an excess of 1a to give 3h, which is obtained in a 9:1 mixture of racemate and meso-isomer; the meso-isomer crystallizes in the space group P21/n. The corresponding diazadiboracyclopentane 3i and the triazadiboracyclopentane 3j are formed from 1a and N-phenyl benzaldimine or azobenzene, respectively. Ethyne and 1a give either the azadiboracyclopentene 4a (1:1) or the diazatetraborabicyclo[3.3.0]octane 3k (1:2). The phosphaalkyne PC-tBu and 1a analogously yield the heterocyclopentene 4c. Theinsertion of SitBu2 into 1a to give the azasiladiboracyclobutane 5a is achieved by applying Li powder and tBu2SiCl2. The hitherto unknown azadi boriridines BN2R2R' (R=tBu; R'=1-iPr, 2-Mes, 2-CMe2Et: 1b-d) were synthesized by the chloroboration of the iminoboranes RBNiPr and RBNR with RBCl2, MesBCl2, and (EtMe2C)BCl2, respectively, and subsequent dechlorination of the isolated and characterized diborylamines Cl-BR-NiPr-BR-Cl (6a), Cl-BR-NR-BMes-Cl (6b), and Cl-BR-NR-B(CMe2Et)-Cl (6c), respectively, with lithium (Mes=mesityl). The azadiboriridine 1b dimerizes to give the diaza-nido-hexaborane 7a, whereas 1c and 1d storable at room temperature. The product 1c crystallizes as a racemate in the space group P21/c; its ring geometry differs from that of the known N-mesityl isomer.
