Borane oxidation/polymerization

Alkynes are reactive toward hydroboration reagents. The most useful procedures involve addition of a disubstituted borane to the alkyne, which avoids complications that occur with borane and lead to polymeric structures. Catechol borane is a particularly useful reagent for hydroboration of alkynes.212 Protonolysis of the adduct with acetic acid results in reduction of the alkyne to the corresponding cw-alkene. Oxidative workup with hydrogen peroxide gives ketones via enol intermediates. 

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

The development of polypyrroles bearing supported diphosphine ligands protected from oxidation by borane groups has been reported.86 The polymer was produced by the electropolymerization of l-(7V-but-4-yl-pyrrol)-l,2-bis(diphenylphosphinoborane) (62) (Fig. 40). These preformed polymeric films lend themselves to the incorporation... 

First, oligo(ethylene oxide) monomethylether was treated with excess BH3-THF complex in THF. After solvent and borane-THF were removed under reduced pressure, the resulting hydroborane with an oligo(ethylene oxide) tail was polymerized with triethyleneglycol in THF at room temperature (r.t.). The polymers obtained were purified by reprecipitation into //-hexane or by washing with diethylether to give colorless or translucent gums in 61—76% yield. 

The peroxide 179 dissociates in the presence of a monomer giving rise to alkoxyl (CO-) and borinate (BO-) radicals, but the latter are believed to be too stable to initiate polymerization. It should be mentioned that the molecular weight continuously increases throughout the process implying the pseudo-living mechanism for chain growth. After the completion of the process borane residue is completely oxidized into diol <2004MM6260>. Thus, the 8-boraindane molecule not only initiates the polymerization, but also is a precursor to two functionalities in the polymer chain. 

The following amine boranes are manufd by the Callery Chemical Co a)Dimethylamine-borane, (CH,)aNH BHS, wh solid b)Tri-methylamine-borane, (CHS)SN BH, wh solid e)Pyridine-borane, CBHSN BHb, col liquid These amine-boranes are relatively stable complexes and are of interest because they act as selective reducing agents, polymerization catalysts, anti-oxidants and stabilizing agents. They may also be used for the prepn of diborane and as petroleum additives. Further information may be obtained from Tech Bull C-200(Ref 2)... 

Based on the excellent solubility and reducing properties of amine boranes, they are often used for the stabilization and purification of industrial materials. Further, they are applied as additives in hydrocarbon fuels and in lubricating oils, as polymerization catalysts, as ingredients in photographic processing and in the electroplating industry.169 High stability towards hydrolysis and oxidation makes cationic boron chelates useful as water-soluble dyes.170... 

Organometallic compounds asymmetric catalysis, 11, 255 chiral auxiliaries, 266 enantioselectivity, 255 see also specific compounds Organozinc chemistry, 260 amino alcohols, 261, 355 chirality amplification, 273 efficiency origins, 273 ligand acceleration, 260 molecular structures, 276 reaction mechanism, 269 transition state models, 264 turnover-limiting step, 271 Orthohydroxylation, naphthol, 230 Osmium, olefin dihydroxylation, 150 Oxametallacycle intermediates, 150, 152 Oxazaborolidines, 134 Oxazoline, 356 Oxidation amines, 155 olefins, 137, 150 reduction, 5 sulfides, 155 Oxidative addition, 5 amine isomerization, 111 hydrogen molecule, 16 Oxidative dimerization, chiral phenols, 287 Oximes, borane reduction, 135 Oxindole alkylation, 338 Oxiranes, enantioselective synthesis, 137, 289, 326, 333, 349, 361 Oxonium polymerization, 332 Oxo process, 162 Oxovanadium complexes, 220 Oxygenation, C—H bonds, 149... 

Controlled radical polymerization (CRP) is an attractive tool, because of the resultant controllability of polymerization, and because of it being a versatile method to synthesize of well-defined polymer hybrids. The three main radical polymerization techniques, ATRP, NMP, and RAFT polymerization, have thus been employed. Other techniques, such as the oxidation of borane groups, have also been studied. In general, using CRP techniques, block copolymers can be synthesized from terminally functionalized PO as PO macroinitiator, and block copolymers can be prepared from functionalized PO produced by the copolymerization of olefins with functional monomers. 

Organoborane complexes have shown a high efficiency for polymerizing vinyl monomers at room temperature as evidenced by numerous investigations developed by Chung et al. [94-97]. The oxidation of organoborane leads to the formation of borane peroxide able to initiate the polymerization ... 

Little is known about the thermal isomerization of organoboranes derived from trienes and higher polyenes. Hydroboration of 1,4,8-nonatriene and its 5-methyl derivative with HjB-THF gives insoluble polymeric products. When this mixture is heated to 210-220°C, bicyclic boranes XI and XIII are formed in good yields, along with other minor bicyclic products. Carbonylation-oxidation of the bicyclic boranes provides 9-decalol (XII) and lO-methyl-9-decalol (XIV) in 73 and 46 % yields, respectively, based on the initial trienes ... 

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