Diborane bromo

In order to allow for a closer approach of the boron centers, the introduction of flat cyclic boryl moieties with reduced steric hindrance has also been pursued. Thus, the reaction of 26 with 9-chloro-9-borafluorene and 5-bromo-10,l 1-di-hydrodibenzo[b,f]borepin resulted in the formation of diboranes 31 and 32 which bear two different boryl moieties at the pen-positions of naphthalene (Scheme 13). " These diboranes have been characterized by multinuclear NMR spectroscopy and X-ray single-crystal analysis. In 31, the boron center of the borafluorenyl moiety is 7i-coordinated by the zp o-carbon of a mesityl group with which it forms a contact of 2.730(3) A (Fig. 8). As a result of this interaction, the boron center involved in this contact is slightly pyramidalized (Xangie = 355.7°). In the case of 32 (Fig. 9), the distance between the boron center of the boracylic moiety and the zpio-carbon of... 

In an effort to prepare bidentate boranes as colorimetric anion sensors, the incorporation of chromophoric boron moieties has also received attention. Reaction of lO-bromo-9-thia-lO-boranthracene 33 with dimesityl-1,8-naphthalenediylborate 26 affords diborane 34 (Scheme 14). This bright yellow diborane is soluble in chloroform, THF and pyridine. It has been fully characterized but its X-ray crystal structure could not be determined experimentally. Its structure was computationally optimized using DFT methods (B3LYP, 6-31 + G for the boron and sulfur... 

Boron tribromide Boron bromide (8) Borane, tribromo- (9) (10294-33-4) Bromobis(dimethylamino)borane Borane, bromobis(dimethylamino)- (8) Boranediamine, 1-bromo-N,N,N, N -tetramethyl- (9) (6990-27-8) Tetrakis(dimethylamino)diboron Diborane(4), tetrakis(dimethylamino)- (8) Diborane(4)tetramine, octamethyl- (9) (1630-79-1)... 

The solvent-free, microwave-assisted coupling of thienyl boronic acids and esters with thienyl bromides, using aluminum oxide as the solid support, served to rapidly check the reaction trends on changing times, temperature, catalyst, and base and easily optimize the experimental conditions to obtain the desired product in fair amounts. This procedure offers a novel, general, and very rapid route to the preparation of soluble thiophene oligomers. Quaterthiophene 265 was obtained in 6 min by reaction of 2-bromo-2,2 -bithiophene with bis(pinacolato)diborane(4) in 65% yield, whereas dithiophene 266 was obtained with 70% yield. The synthesis of new chiral 2,2 -bithiophenes also was reported. The detailed... 

Peel and Sutherland [34] synthesized the lactone acid (21) starting with the formation of the epimeric diformates by a Prins reaction of norbornadiene and paraformaldehyde to give (22a). Hydrolysis and Jones oxidation of (22a) then gave the keto acid (22b) which underwent ring opening with hydrogen bromide in acetic acid to the bromo compound (23). Baeyer-Villiger oxidation of the latter and addition of sulphuric acid to the reaction mixture followed by work up with alkali afforded an overall conversion to (21) of which the p-bromo-phenacyi ester was converted by the sequence - p-phenylbenzoylation, reduction with zinc and acetic acid and diborane reduction - to the alcohol (14d), previously taken forward to the aldehyde (lb) by Corey. 

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