Dienes, hydroboration polymerization

Hydroboration polymerization between diene monomers and 2,4,6-trimethylphenylborane (mesitylborane)6 or 2,4,6-triisopropylphenylborane (tripyl-borane)7 gave organoboron main-chain polymers (scheme 3). The polymerization was... 

In the present hydroboration polymerization, thexylborane was employed as a monoalkylborane (bifunctional hydroborane) component because thexylborane is known to be stable enough after distillation. As a diene monomer, relatively longer chain dienes were used to avoid the... 

As summarized in Table 1, this hydroboration polymerization can be applied to various combinations of dienes such as 1,9-decadiene, p-divinylbenzene, p-diallylbenzene, bis(allyl ether)s of ethylene glycol, tetramethylene glycol, triethylene glycol, hydroquinone and bisphenol-A with thexylborane to produce the corresponding organoboron polymers. 

Acetylenes are known to be reactive toward hydroboration reaction as well as dienes. Accordingly, hydroboration polymerization with monoalkylborane can also be applied to diynes. Generally, the reactivity of a terminal acetylene group toward hydroboration is quite different from that of an internal acetylene group. That is, the terminal... 

HYDROBORATION POLYMERIZATION OF DIENES WITH MONO-BROMOBORANE... 

HYDROBORATION POLYMERIZATION OF DICYANO COMPOUNDS The organoboron polymers prepared by hydroboration polymerization of dienes or diynes are relatively unstable toward air as mentioned before. On the other hand, the preparation of stable boron-containing polymers has been an attractive target as polymeric materials, for which... 

Recently, we explored a novel polyaddition between dienes and monoalkylboranes and termed this hydroboration polymerization (18). Diynes and dicyano compounds can also be used in this hydroboration polymerization. The organoboron polymers obtained are effectively converted to polyalcohols or polyketones. In other words, polymers having organoboron units in the main chains can be expected to be reactive polymers. Here, the scope of these hydroboration polymerizations is viewed as methodologies for the preparation of organoboron polymers. 

As a typical example for hydroboration polymerization of internal diyne, the reaction of 3,9-dodecadiyne and thexylborane was carried out in THF at 0°C under nitrogen (20). The polymerization behavior was quite similar to hydroboration polymerization of dienes. The organoboron polymer obtained was a colorless wax and soluble in common organic solvents such as benzene, THF or chloroform. An IR spectrum of the polymer showed the absorption band assignable to C=C bond, which was also supported by H- and B-NMR spectra. 3,8-Undecadiyne and 3,10-tridecadiyne were also used in hydroboration polymerization with thexylborane to produce the corresponding organoboron polymers. 

As an alternative method for the preparation of polyalcohols from organoboron polymers, dichloromethyl methyl ether (DCME) can be used (23). Various organoboron polymers prepared by hydroboration polymerization of dienes and thexylborane were reacted with DCME at 0°C in THF followed by treatment with lithium triethylmethoxide. After oxidative treatment with NaOH and H2O2, the corresponding poly(alcohol)s were obtained. The... 

Hydroboration of a,C0-dienes with monoalkylboranes gives reactive organoboron polymers which can be transformed into polymeric alcohols or polyketones by carbonylation, cyanidation, or the DOME reaction followed by oxidation (446—448). 

Dienes. The bifunctionality of dienes makes their hydroboration more complex than that of simple alkenes. Competing hydroboration of the two double bonds may lead to mixtures of products arising from mono- or diaddition. Additionally, cyclic or polymeric organoboranes may be formed. Differences in the reactivity of the two double bonds and the use of appropriate hydroborating agents, however, may allow selective hydroboration.29,330... 

Cyclic dialkylboranes are prepared by hydroboration of dienes with 1 1 HjB THF. Trifunctional boranes give with difunctional dienes polymeric organo-boranes. Fortunately, these products can be transformed into monomers or dimers by further reaction. Thus, the hydroboration product obtained from 1,3-butadiene is polymeric " . The initial products, which are dumbbell-shaped organoboranes, are cleaved by the remaining borane to give the polymer. 

Octadiene and higher a,co-dienes with 1 1 HjB-THF leads to polymeric material. Low yields of cyclic products are also obtained in the hydroboration of mixed dienes, e.g., 4-vinylcyclohexene or limonene (see Table 7), but 1,5-cyclooctadiene undergoes cyclic hydroboration in high yield. A mixture of 9-borabicyclo[3.3.1] nonane (9-BBN) and 9-borabicyclo[4.2.1]nonane is formed. Other intermediates are also observed by B NMR. Upon heating, the latter compound is transformed " to the more thermodynamically stable 9-BBN ... 

Hydroboration of a.,oi-dienes. Cyclic hydroboration of ,cu-dienes can be effected with this reagent. The initial product is often polymeric, but six- to eight-membered cyclic B-chloroboracycloalkanes can be obtained after depolymerization by distillation in good yields. The B-chloroboracycIoaikanes (2) and (3) from 1,4-pentadiene (1) were transformed into the cyclic ketones (6) and (7) by reaction with a,a -dichloromethyl methyl ether (5, 200 203) followed by oxidation. ... 

Polymeric products are also obtained the quantity depends on the type of diene and the experimental conditions. Heating above 120° C degrades a large part of the high-viscosity polymers into distillable boron heterocyclics through a dehydroboration-hydroboration equilibrium 10) ... 

Hydroboration of terminal diyne gives organoboron polymer having branched structure due to the further hydroboration reaction toward the initially formed vinylborane structures. That is, terminal diynes are taken to have a potential as a multifunctional monomer. When the polymerization between 1,7-octadiene and thexylborane was carried out in the presence of a small amount of 1,7-octadiyne, the molecular weights of organoboron polymers were found to be increased when the ratio of diyne/diene was increased [5]. 

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