Diborane Subject

I began graduate studies at the University of Chicago in 1936. At that time, the structure of diborane was a subject of considerable study and... 

A syn displacement of the bromine by benzylamine in the presence of triethylamine led, by a Sn2 reaction, to the a and p amino compounds which were separated into 326 (18%) and 327 (81%) respectively. The dichloroacetamide 328 derived from the latter, when subjected to the action of tri-n-butyltinhydride (2eq) and 2,2 -azobisisobutyronitrile underwent a 5-ero ring closure to furnish via the radical 329, the hydrooxindole 330 (51%) and significant amount of the rearrangement product 331 (30%). The latter is believed to be formed by fragmentation of the cyclohexadienyl radical 332 generated from the cyclohexyl radical 329. On diborane reduction, 330 provided the cis hydroindole 333, which on 0,N-debenzylation afforded ( )-c -fused bicyclic aminoalcohol 334, a compound that had been previously cyclised with formaldehyde to ( )-elwesine (320) by Stevens et al [85]. 

A series of mixed tetra(amino)diborane(4) compounds bearing pyrrolyl, indolyl, and carbazolyl substituents besides dimethylamino groups has been prepared and subjected to reduction with elemental lithium in the... 

When the evaporation is complete, the 0°C. trap will contain a few milliliters of diglyme the — 196°C. trap will have trapped-out diborane (caution) and the — 126°C. trap will have retained the dimethyltin dihydride together with traces of diglyme and diborane. The crude product is accordingly subjected to a second vacuum fractionation through clean, 0°C. and — 126°C. vacuum traps into the same — 196°C. trap. The diborane collected in the — 196°C. trap is destroyed as described in Sec. A. The colorless, volatile liquid product is identified from its vapor-phase infrared spectrum14 and from its refractive index, nf> 1.4475, literature,2 n 1.4480, as dimethyltin dihydride. The yield is 8.25 g. (0.055 mole, 96%). 

The concepts discussed above, permit proposals to be made concerning the structure of other boron hydrides which have not been subjected to such an extensive experimental investigation as has diborane. The proposed formulae fall into two groups, that favouring the resonance of structures analogous to those represented schematically for diborane in IV to VIII (Syrkin and Dyatkina ) and that employing the concept of the protonated double bond (Pitzer ). ... 

The allylic carbamate 193 formed as shown in Scheme 17 can be exploited in the synthesis of a pancratistatin analogue. Thus, Suzuki-Miyaura cross-coupling of this carbamate with aryl boronic acid 61 (Scheme 18) afforded the expected arylated cyclohexene 200 (87%) that upon sequential treatment with diborane, alkaline hydrogen peroxide, aqueous acid then acetic anhydride gave the triacetate 201 (42%). Subjecting this last compound to the Bischler-Napieralski reaction... 

Diborane (or, more correctly, borane) may be regarded as existing already preformed in tetrahydroborates. Metal tetrahydroborates have been the subject of a recent article in this series (163). A variety of methods for releasing diborane from them are now known, although aqueous and hydroxylic reagents that react with it are useless. Until recently, however, all reported methods incorporated one or more avoidable practical disadvantages. 

Diborane(6) catalyzes the polymerization of imidazole-borane (see Section 2.2.4.3, p. 19), and it forms HBNH when subjected to an a.c. discharge plasma in the presence of NH3 [9, 10]. Boron phosphide, BP, is deposited as single crystal wafers when diborane(6) is thermally decomposed in the presence of PH3 in an H2 atmosphere [11]. Solvent-free diborane(6) reacts with CH3-U(r 5-C5H5)3 via the intermediate (r 3-CH3-BH3)U(r 5-C5H5)3 to form (r 3-BH4)U(r 5-C5H5)3 [12]. 

It is assumed that the reader has had some acquaintance with boron hydride chemistry and is somewhat familiar with the structures and bonding characteristics found in the well-known boron hydrides, e.g., diborane, tetraborane(lO), pentaborane(9), pentaborane(ll), and decaborane(14). For a recent review of the subject, a volume by Lipscomb (17) is highly recommended. In addition, surveys of related topics, as well as earlier reviews on the present subjects, are advised for completeness (7,15,16, 22-49). 

Carbon Monoxide- C—B)Borane BH3CO The unstable compound carbon monoxide-(C—B)borane (12), BH3CO, prepared from diborane and carbon monoxide under elevated pressures (20S), has been the subject of intensive spectroscopic investigations. Electron diffraction measurements (204) indicate that the molecule has its B—C—O... 

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