Polymer borylated

The synthesis of luminescent organoboron quinolate polymers (21) (Fig. 15) via a three-step procedure starting from a silylated polystyrene has been communicated. The synthesis was initiated by the highly selective borylation of poly (4-trimethylsilylstyrene) (PS-Si), followed by the replacement of the bromine substituents in poly(4-dibromoborylstyrene) (PS-BBr) with substituted thienyl groups (R = H, 3-hexyl, 5-hexyl). In the final step, the 8-hydroxyquinolato moiety was introduced. The hexyl-substituted polymers efficiently emitted light at 513-514nm upon excitation at 395 nm.40... 

Hartwig and Hillmyer have recently reported the Rh-catalyzed borylation of polyolefins to yield boronate-functionalized polymers (58) (Fig. 37) in a single step.83 The number-average molecular weight of the borylated polymer that was obtained at a B2pin2 polyethylethylene ratio of 0.3 was found to be the highest (Mn = 52,000 and PDI = 1.09) among the developed boronate-functionalized polyolefins. 

Figure 37 The boronate-functionalized polymer (58) obtained by the Rh-catalyzed borylation of polyolefins. (Adapted from ref. 83.)...

We have reported that the reaction of 2,4,6-tri(chloro)borazine CI3B3N3H3 with three equivalents of tris(isopropylamino)borane B(NHPr )3 led to the formation of 2,4,6-tri[bis(isopropylamino)boryl(isopropyl)amino]borazine 11 [Fig. 5(a)] in quantitative yield.26,27 The subsequent polycondensation carried out in vacuo up to 150°C, led to the formation of the polymer 12 containing B3N3 rings linked either through direct B—N interring bonds (minor pathway) or three-atoms —N—B—N— bridges... 

The rhodium-catalyzed borylation of alkanes is applied to regiospecific functionalization of polyolefines.165,165a The reaction of polypropylenes (atactic, isotactic, and syndiotactic) with B2pin2 in the presence of Cp Rh( 74-C6Me6) catalyst at 200 °G affords the borylated polymers, which are treated with basic hydrogen peroxide in a mixture of THF and H20 to oxidize the boronate esters to the corresponding alcohols (Scheme 20). The hydroxylated polymers contain 0.2-1.5% hydroxymethyl side-chains. 

A convenient direct route has recently been described for obtaining regioregular polyalkylthiophenes using a tandem iridium-catalyzed borylation to produce the monomer, and a palladium-mediated coupling to produce the polymer [68]. The treatment of substituted thiophenes with B2pin2 in the presence of [lrCl2(COD)]2/ 4,4 -di-tert-butyl-2,2 -bipyridine (DTBPY) provided the expected monomer in 97% yield (Scheme 7.35). 

In the first approach, 0-(carboxymethyl)cellulose (47) has been converted into the acyl azide (48) and thence, by treatment with m-aminopheny lboronic acid, into the borylated form 49, to give a polymer... 

Solms and Deuel95 initially prepared a wholly synthetic, borylated polymer by using m-phenylenediamine, p-aminophenylboron dichloride, and formaldehyde, and they investigated carbohydrate separations on it, but addition polymers have usually been favored. Thus, ribonucleosides and deoxyribonucleosides have been efficiently separated on a column of a mixed copolymer of the methacroyl derivatives96 51 and 52, and the method has been extended to... 

Borylated ferrocenes have been exploited by Wagner as building blocks for the assembly of macrocycles and coordination polymers (Scheme 15). Treatment of the diborylated ferrocene l,L-fc(BMe2)2 with the bifunctional aromatic amines pyrazine and 4,4 -bipyridine, respectively, led to spontaneous and reversible formation of (89) and related ferrocenylborane polymers.The polymeric nature of... 

Processable boryl-borazine based polymers. An alternative approach was undertaken in order to prepare polyborazines with multi-atom bridges between the rings. The reaction of 2,4,6-trichloroborazine with BfNHPr h yields a polymer (3) in which the borazine rings are connected through N-B-N bridges (Scheme 3). 

Another resin-capture approach has been pubhshed in relation to the synthesis of tetrasubstituted ethylenes via Suzuki coupling reactions (Scheme 20) [42, 53]. A 25-member hbrary was synthesized using five alkynes, five aryl halides, and a polymer-bound aryl iodide. The alkynes 55 were converted into bis(boryl)alkenes 56 in solution, and the crude intermediates were used in Suzuki reactions with an excess of aryl halide. When all of the bis(boryl)alkene 56 had been consumed, the aryl iodide resin 59 was added to the reaction mixture and the reaction continued on the solid support. Side products such as 58, arising from a double Suzuki reaction, remained in solution and could be washed away. Compounds 60 were cleaved from the polymer using trifluoroacetic acid and products 61 were obtained in > 90% purity. 

Introducing boryl substituents into a polymer not only influences polymer physical properties but also provides a reactive functional group that can undergo further chemical modification. The development of boron-fimctionahzed polymers has been slow compared with that of other ffinc-tionahzation methods of diene polymers due to the hydrolytic and oxidative sensitivity of many boron-containing molecules. However, new synthetic methods developed over the years have made easier the synthesis of boron-containing polymers with better long-term stability. Recently, the unique electronic and photophysical properties and Lewis acidic character of boron-containing polymers have attracted attention for the development of novel optical and sensor materials. " ... 

One facile way to incorporate boryl moieties into diene-containing polymers is via hydroboration. The addition of a B—H bond to C=C bonds via hydroboration is not stricdy a metal-mediated process, but catalyzing it with transition metal complexes provides a number of benefits. For example, transition metal catalysts can alter selectivity of hydroboration and provide alternatives for manipulating regio-, stereo-, and chemoselectivity. Additionally, they can help accelerating the addition of boryl substituents when the reaction rates are very slow—e.g., addition of catecholborane. 

The boryl groups installed on the aromatic polymers are useful synthetic intermediates for conversion to other polar functional groups. For example, they can be oxidized to give hydroxylated polymers and a variety of polar group-containing polymers via either direct functional group transformations or palladium-catalyzed Suzuki cross-coupHng reactions with appropriate phenyl bromides (Fig. 25). This transition metal-catalyzed polymer... 

Chang Y, Lee HH, Kim SH, Jo TS, Bae C. Scope and regioselectivity of iridium-catalyzed C—H borylation of aromatic main-chain polymers. Macromolecules. 2013 46 1754-1764. 

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