Polyesters lactones

Carothers and colleagues were the first to explore the ROP of lactones. Many research laboratories have now been involved in this research area. The ROP of lactones is the method of choice for the production of biocompatible and biodegradable polyesters. Lactones are ambidentate and the polymerization may proceed by either alkyl-oxygen or acyl-oxygen scission. Evidence in favor of both types of scission is reported in the literature. 

Another principal use of ketene is in the production of sorbic acid [110-44-1] (80,81). In this process, which requires an acidic or manganese(II) catalyst, ketene adds to crotonaldehyde [123-73-9] (8) with subsequent conversion of the P-lactone and the polyester to sorbic acid (qv) (9). 

Chiral Lactones and Polyesters. Similar to intermolecular reactions described previously. Upases also catalyze intramolecular acylations of hydroxy acids the reactionsults in the formation of lactones. 

Increasing the molecular weight of polyester (or polyether) or changing its chemical composition could lower the Tg of the TPU and decrease the crystallinity of the polymer. For example, a TPU composed of poly(S-lactone), MDI, and 1,4-butanediol was found to have the lowest degree of crystallinity and, therefore, the best compatibility with PVC when the hard segment in it is 36% by weight [10]. 

Although no small molecule gets eliminated, the reaction can be considered a condensation polymerization. Monomers suitable for polymerization by ring opening condensation normally possess two different functional groups within the ring. Examples of suitable monomers are lactams (such as caprolactam), which produce polyamides, and lactons, which produce polyesters. 

Depending on dieir structure, properties, and syndietic methods, degradable polyesters can be divided into four groups poly(a-esters), poly(fi-esters), poly(lactones), and polyesters of aliphatic diols and diacids. 

The enantioselectivity was greatly improved by the copolymerization with 7- or 13-membered non-substituted lactone using lipase CA catalyst (Scheme 8) the ee value reached ca. 70% in the copolymerization of (3-BL with DDL. ft is to be noted that in the case of lipase CA catalyst, the (5 )-isomer was preferentially reacted to give the (5 )-enriched optically active copolymer. The lipase CA-catalyzed copolymerization of 8-caprolactone (6-membered) with DDL enan-tioselectively proceeded, yielding the (/ )-enriched optically active polyester with ee of 76%. 

Reactive polyesters were enzymatically synthesized. Lipase catalysis chemoselecfively induced the ring-opening polymerization of a lactone having exo-methylene group to produce a polyester having the reactive exo-methylene group in the main chain (Scheme 16). This is in contrast to the anionic... 

Terminal-functionalized polymers such as macromonomers and telechelics are very important as prepolymer for construction of functional materials. Single-step functionalization of polymer terminal was achieved via lipase catalysis. Alcohols could initiate the ring-opening polymerizahon of lactones by lipase catalyst. The lipase CA-catalyzed polymerizahon of DDL in the presence of 2-hydroxyethyl methacrylate gave the methacryl-type polyester macromonomer, in which 2-hydroxyethyl methacrylate acted as initiator to introduce the methacryloyl group quanhtatively at the polymer terminal ( inihator method ).This methodology was expanded to the synthesis of oo-alkenyl- and alkynyl-type macromonomers by using 5-hexen-l-ol and 5-hexyn-l-ol as initiator, respechvely. 

In vitro synthesis of polyesters using isolated enzymes as catalyst via non-biosynthetic pathways is reviewed. In most cases, lipase was used as catalyst and various monomer combinations, typically oxyacids or their esters, dicarboxylic acids or their derivatives/glycols, and lactones, afforded the polyesters. The enzymatic polymerization often proceeded under mild reaction conditions in comparison with chemical processes. By utilizing characteristic properties of lipases, regio- and enantioselective polymerizations proceeded to give functional polymers, most of which are difficult to synthesize by conventional methodologies. 

Polyester syntheses have been achieved by enzymatic ring-opening polymerization of lactide and lactones with various ring-sizes. Here, we focus not only on these cyclic esters but also other cyclic monomers for lipase-catalyzed ringopening polymerizations. Figure 8 summarizes cyclic monomers for providing polyesters via lipase catalysis. 

The copolymerization of lactones took place through enzyme catalysis [92]. The copolymerization of e-CL with d-VL catalyzed by lipase PF affords the corresponding copolymer having a molecular weight of several thousand. From 13C NMR analysis, the copolymer was found to be of random structure having both units, suggesting the frequent occurrence of transesterifications between the polyesters. In the copolymerization of 8-OL with e-CL or DDL, random copolyesters were also formed [84], whereas the copolymer from e-CL and PDL was not statistically random [88]. 

A 1992 patent describes the carbonylation of EO to yield /3-propiolactone using a mixture of Co2(CO)8 and 3-hydroxypyridine.982 A recent re-investigation of this system has indicated that the major product is the alternating copolymer, a polyester, catalyzed by the [Co(CO)4] anion (Scheme 24).983 The synthesis of lactones via this methodology has successfully been achieved using Lewis acidic counter-cations (Scheme 25) 984,985 a similar strategy allows /3-lactams to be... 

A naturally occurring lactone, ambrettolide, was polymerized (110) employing the WCl6/(CH3)4Sn catalyst in a molar ratio of monomer/W/ Sn of 50/1/5, affording a high molecular weight unsaturated polyester. 

Conversions of about 80% were obtained within a few minutes at 90°C. The polymer could also be cleaved by cross-metathesis with an excess of 4-octene which gave, as the main product, 9-tridecenyl-7-undecenoate, thus confirming the structure assignment as indicated in Eq. (62). The unsaturated lactone was also copolymerized with cyclooctene, 1,5-cy-clooctadiene, and cyclopentene under the previously stated conditions to afford linear copolymers which were high molecular weight, unsaturated, rubbery polyesters (110). 

The /3-lactone dimer of dimethylketene can be prepared by pyrolysis of its polyester, which is formed by the base-catalyzed polymerization of dimethylketene.3"6 In addition to the rearrangement of the normal dimer described above,6 the direct dimerization of dimethylketene in the presence of aluminum chloride3 or trialkyl phosphites7 leads to the /3-lactone dimer. 

In the presence of catalytic amounts of sodium methoxide, dimethylketene /3-lactone dimer is polymerized at moderate temperature to a polyester.3 At higher temperatures (above 100°), disproportionation to the cyclic trimer, hexamethyl-1.3,5-cyclohexanetrione, takes place.9 Addition of a stoichiometric amount of sodium methoxide to the lactone dimer generates the sodium enolate of methyl 2,2,4-trimethyl-3-oxovalerate. This reaction provides a convenient entry into certain ester anion chemistry that formerly required the use of a strong base like tritylsodium.10... 

On the other hand, in cyclic ethers (alkene oxides, oxetans, tetrahydrofuran) and formals the reaction site is a carbon-oxygen bond, the oxygen atom is the most basic point, and, hence, cationic polymerization is possible. The same considerations apply to the polymerization of lactones Cherdron, Ohse and Korte showed that with very pure monomers polyesters of high molecular weight could be obtained with various cationic catalysts and syncatalysts, and proposed a very reasonable mechanism involving acyl fission of the ring [89]. 

Activity in the field was, however, expanding. For example, in 1927 Drew and Haworth (65) obtaind a crystalline polymeric powder by the action of hydrogen chloride on the lactone of 2,3,4-trimethyl-l-arabonic acid. Citing the increase in melting point and molecular weight, and loss of specific optical rotation, they ascribed a cyclic, high polymer structure to this polyester. 

The ring-expansion carbonylation of epoxides is the most widely studied field in the epoxide carbonylation chemistry since the product lactones are highly attractive targets particularly, /1-lactones are useful compounds due to their versatility in organic synthesis [ 14,15] as well as their utilization as monomers to produce poly(3-hydroxyalkanoate)s, naturally occurring biodegradable polyesters [16-19]. 

Poly(3-hydroxyalkanoate)s have potential for application to engineering plastics endowed with biodegradable nature. One of the synthetic approaches to the polyesters is the ring-opening polymerization of -substituted /3-lactones which can be effectively produced by ring-expansion carbonylation of epox-... 

D-Glucaric acid, directly produced by nitric oxidation of glucose or starch, is usually isolated as its 1,4-lactone. The technical barrier to its large-scale production mainly includes development of an efficient and selective oxidation technology to eliminate the need for nitric acid as the oxidant. Because it represents a tetrahydroxy-adipic acid, D-glucaric acid is of similar utility as adipic acid for the generation of polyesters and polyamides (see later in this chapter). 

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