1,4-Polyketone

In this chapter we will discuss some aspects of the carbonylation catalysis with the use of palladium catalysts. We will focus on the formation of polyketones consisting of alternating molecules of alkenes and carbon monoxide on the one hand, and esters that may form under the same conditions with the use of similar catalysts from alkenes, CO, and alcohols, on the other hand. As the potential production of polyketone and methyl propanoate obtained from ethene/CO have received a lot of industrial attention we will concentrate on these two products (for a recent monograph on this chemistry see reference [1]). The elementary reactions involved are the same formation of an initiating species, insertion reactions of CO and ethene, and a termination reaction. Multiple alternating (1 1) insertions will lead to polymers or oligomers whereas a stoichiometry of 1 1 1 for CO, ethene, and alcohol leads to an ester. 

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Copolymerization to form polyketones proceeds by the carbonylation of some alkenes in the absence of nucleophiles. Copolymerization of CO and norbornadiene takes place to give the polyketone 28(28]. Reaction of ethylene and other alkenes with CO affords the polyketones 29. The use of cationic Pd catalysts and bipyridyl or 1,10-phenanthroline is important for the polymerization [29-31]. 

Ketenes. Derivatives of the compound ketene, CH2=C=0, are named by substitutive nomenclature. For example, C4Hc,CH=C=0 is butyl ketene. An acyl derivative, such as CH3CH2—CO—CH2CH=C=0, may be named as a polyketone, l-hexene-l,4-dione. Bisketene is used for two to avoid ambiguity with diketene (dimeric ketene). 

Polyketones in which two or more contiguous carbonyl groups have rings attached at each end... 

Ttihaloacyl aromatics have been prepared by Friedel-Crafts acylation of aromatics with CX COCl (X = Cl, Br) in the presence of AlCl. They are used as monomers in the preparation of polycarbonates, polyesters, polyamides, polyketones, and polyurethanes (91). 

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). 

In addition to polyamide, lamination inks ordinarily contain modifiers such as polyketone resin, plasticizer, and wax to impart specific properties such as block resistance and increased bond strength. Because laminating inks are usually reverse-side printed and end-up sandwiched between films, gloss is not a primary requirement. Water-base laminating inks that will meet the U.S. EPA emission requirements and have the correct functional properties are currently under development. 

Other Rea.ctions, The photolysis of ketenes results in carbenes. The polymeriza tion of ketenes has been reviewed (49). It can lead to polyesters and polyketones (50). The polymerization of higher ketenes results in polyacetals depending on catalysts and conditions. Catalysts such as sodium alkoxides (polyesters), aluminum tribromide (polyketones), and tertiary amines (polyacetals) are used. Polymers from R2C—C—O may be represented as foUows. 

An important direct use of phosgene is in the preparation of polymers. Polycarbonate is the most significant and commercially valuable material (see Polycarbonates). However, the use of phosgene has been described for other polymer systems, eg, fiber-forming polymeric polyketones and polyureas (90,91). 

Property Units Aliphatic polyketone Acetal Nylon 66 conditioned... 

The presence of the either linkages is sufficient to allow the material to be melt processed, whilst the polymer retains many of the desirable characteristics of polyimides. As a consequence the material has gained rapid acceptance as a high-temperature engineering thermoplastics material competitive with the poly-sulphones, poly(phenylene sulphides) and polyketones. They exhibit the following key characteristics ... 

The polyetherimides are competitive not only with other high-performance polymers such as the polysulphones and polyketones but also with polyphenylene sulphides, polyarylates, polyamide-imides and the polycarbonates. 

The use of PBT as an engineering material is more a consequence of a balance of good properties rather than of a few outstanding ones. It does not possess the toughness of polycarbonate, the abrasion resistance of an aliphatic polyamide, the heat resistance of a polysulphone, polyketone or poly(phenylene sulphide) or... 

It has already been shown (e.g. Chapters 20 and 21) that the insertion of a p-phenylene into the main chain of a linear polymer increased the chain stiffness and raised the heat distortion temperature. In many instances it also improved the resistance to thermal degradation. One of the first polymers to exploit this concept commercially was poly(ethylene terephthalate) but it was developed more with the polycarbonates, polysulphone, poly(phenylene sulphides) and aromatic polyketones. 

With a somewhat lower level of heat resistance but with many properties that make them of interest as engineering materials alongside the polycarbonates, polysulphones, poly(phenylene sulphides) and polyketones are the so-called polyarylates which are defined as polyester from bis-phenols and dicarboxylic acids. 

Over the years polymers have been produced suitable for use at progressively higher temperatures. Where this is a requirement, it is usual first to decide whether a rubbery or a rigid material is required. If the former, this has been dealt with by the author elsewhere." If the latter, it is usually convenient to look in turn at polycarbonates, PPO-based materials, polyphenylene sulphides, polysul-phones, polyketones such as PEEK and PEK, polyamide-imides, poly-phthalamides, fluoropolymers, liquid crystal polymers and polyimides. 

The selective formation of the 3-monosemicarbazones of polyketonic steroids can be achieved only in the presence of 21-acetoxy-20-ketones by the use of nonbuffered conditions. Partial hydrolysis of 3,20-bissemicar-bazones can be achieved with acetic anhydride in pyridine "" to yield the 3-semicarbazone. Kinetic studies on the rates of formation of Girard hydra-zones showed that the A" -3-ketone is less reactive than the saturated 3- and 6-ketones, as reactive as the 7- and 17-ketones and more reactive than the 20- and 12-ketones. ... 

Some polyketones have been used to synthesize diisoxazolyl alkanes, e.g., 1,4-di- (5 -phenyl-3 -isoxazoly 1) butane. ... 

The acetate labeling results clearly demonstrated a polyketide origin for the naphthoate fragment. This resulted in the hypothesis that the first enzyme-free intermediate in azinomycin biosynthesis would be naphthoate 102, with condensation to fonn a polyketone chain, reduction, cyclization, and dehydration/aromati-... 

Polyketone/Glass Potyethereltierketone (PEEKyGlass Polyphenylene SullideA3tess Polyiroide... 

Of the 4-methylene-1,3-dioxolanes reported thus far (Table 4.6), only the 2,2-diphenyl derivative (50) is reported to give the polyketone quantitatively (Scheme 4.32). This requires temperatures in excess of 120 °C in bulk polymerization."... 

Structural and magnetic studies of polynuclear transition metal p-polyketonates. M. D. Glick and R. L. Lintvedt, Prog. Inorg. Chem., 1976, 21, 233-260 (51). 

Polyisothiouronium group chelating resins mineral processing, 6,826 Polyketones metal complexes, 2, 399 Poly(L-lysine) metal complexes, 2, 764 Polymerization solid state, 1, 470 Polymers... 

Compared with the tert-butyl substitutes PEEK, carbonyl-functionalized polyketones can be converted to the target polyketones at relatively mild conditions. 

The Suzuki reaction was also used to prepare the polyketone since this particular reaction tolerates the subsequent step (Scheme 6.19).135 Palladium-catalyzed cross-coupling of aromatic diacid chlorides and bis(trimethylstannane) monomers was utilized to prepare poly(arylene ether ketone)s.136... 

Recently developed catalyst systems make it possible to construct carbon (.v/>2 )-catbon (sp3) bonds and carbon-nitrogen bonds under mild conditions (Scheme 9.14).19,20 These new developments have also been incorporated into step-growth polymerization. Kanbara et al. reported the synthesis of polyanilines and related polymers in 1996 (Scheme 9.15).21 Wang and Wu reported the synthesis of polyketones in 1999 (Scheme 9.16).22... 

Although only several reports appeared employing these reactions for polymerization, they could potentially be used for the synthesis of different types of polyamines and polyketones, including optically active ones with main-chain chirality. 

Although the most recent modifications of the Prelog condensation of 1,3-dike-tones and 1,3,5-triketones, for example that of acetylacetone with dimethyl 1,3-acetonedicarboxylate in the presence of NaOH in H2O, afford substituted benzenes such as 1486 in up to 94% yield (Scheme 9.22) and coumarins [40], these condensations of highly substituted polyketones with the corresponding aromatic systems might also be effected in the presence of HMDS 2/TCS 14 or TMSOTf... 

Palladium(II) complexes possessing bidentate ligands are known to efficiently catalyze the copolymerization of olefins with carbon monoxide to form polyketones.594-596 Sulfur dioxide is an attractive monomer for catalytic copolymerizations with olefins since S02, like CO, is known to undergo facile insertion reactions into a variety of transition metal-alkyl bonds. Indeed, Drent has patented alternating copolymerization of ethylene with S02 using various palladium(II) complexes.597 In 1998, Sen and coworkers also reported that [(dppp)PdMe(NCMe)]BF4 was an effective catalyst for the copolymerization of S02 with ethylene, propylene, and cyclopentene.598 There is a report of the insertion reactions of S02 into PdII-methyl bonds and the attempted spectroscopic detection of the copolymerization of ethylene and S02.599... 

Devasagayam, T.P.A., Werner, T., Ippendorf, H., Martin H.-D., and Sies, H. 1992. Synthetic carotenoids, novel polyene polyketones and new capsorubin isomers as efficient quenchers of singlet molecular oxygen. 

Since 1985, several thousands of publications have appeared on complexes that are active as catalysts in the addition of carbon monoxide in reactions such as carbonylation of alcohols, hydroformylation, isocyanate formation, polyketone formation, etc. It will therefore be impossible within the scope of this chapter to review all these reports. In many instances we will refer to recent review articles and discuss only the results of the last few years. Second, we will focus on those reports that have made use explicitly of coordination complexes, rather than in situ prepared catalysts. Work not containing identified complexes but related to publications discussing well-defined complexes is often mentioned by their reference only. Metal salts used as precursors on inorganic supports are often less well defined and most reports on these will not be mentioned. 

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