5-lactone initiation

J. P., Anionic pol3nnerization of lactones initiated by alkali graphitides. 1 Polymerization of e-caprolactone initiated by KC24, J. Polym. Sci.. Part A Polym. Chem.. 21. 923-936, 1983. 

Table 2 Ring-opening polymerization of lactones initiated by lanthanide complexes (CL = e-caprolactone LA = lactide TMC = trimethylene carbonate). 

Polymerizations of six- and four-membered lactones initiated with aluminum porphyrins [(TPP)AlX, 1] proceed via (porphinato)aluminum alkoxide and car-boxylate as the growing species, respectively (Schemes 9 and 10) [74,75] to give polyesters with narrow MWD, although it is well known that the polymerization... 

As described in the above section, the concept of immortar polymerization in the polymerizations of epoxides and lactones initiated with aluminum porphyrin in the presence of a protic compound has been developed where polymers of uniform molecular weight are formed with the number of the molecules equal to the sum of those of aluminum porphyrin and the protic compound [83]. This is due to the rapid, reversible chain transfer reaction between the molecules of growing polymer and the protic compound, which takes place much faster than the propagation reaction. In the presence of 1-propanethiol (PrSH) as the protic compound, the polymerization of PO ([PO]o/[HX]o/[17 (X=SPr)]o=400/10/l) proceeded to 93% conversion in 45.5 h at room temperature under irradiation, producing a polymer with Mn and Mw/Mn of 1660 and 1.11, respectively. The number of the polymer molecules relative to that of 17 (X=SPr) as estimated from Mn and the yield of the polymer [84], is... 

According to this mechanism, the potassium anion attacks the 3 lactone ring to cleave the CH2-CH2 bond and form a carbanlon. This anion, which can exist in a tautomeric equilibrium with its enolate form, reacts with the next 6-lactone monomer by the opening of the alkyl-oxygen bond. The propagation reaction, therefore, proceeds by reaction of the carboxylate anion active centers. Experimental data, to be reported later, provides evidence for this unusual C-C bond-breaking reaction in the monomer and for two types of active species, which are responsible for the course of the lactone initiation and polymerization reactions that occur. 

Pyrones are in many ways best viewed as unsaturated lactones, and as such they are easily hydrolysed by aqueous alkali 4-pyrones, too, easily undergo ring-opening with base, though for these vinylogous lactones, initial attack is at C-2. ... 

The polymerisation of lactones initiated by hydroxyl groups is possible in the absence of any catalyst, but it needs higher reaction temperatures (160-180 °C). 

M. Osaki, Y. Takashima, H. Yamaguchi, A. Harada, Polymerization of lactones initiated by cyclodextrins effects of cyclodextrins on the initiation and propagation reactions. Macromolecules, 2007, 40, 3154-3158. 

Ketenes are another type of unsaturated molecules of high electron deficiency and structural strains therefore, they are very reactive for the [2+2] cycloaddition. The most common [2+2] cycloaddition involving ketenes are Staudinger [2+2] Cycloadditions to form fi-lactones, initially reported in 1911, and the dimerization of ketenes." Besides the easy cycloaddition with imine, as shown in the Staudinger [2+2] Cycloaddition, ketenes can also react with aldehydes to afford /3-lactones. It has been found that high diastereoselectivity can... 

Various cychc esters have been subjected to hpase-catalyzed ring-opening polymerization (ROP), notably of four- to 17-membered nonsubstituted lactones. Initially, it was shown that medium-sized lactones, 5-valerolactone (5-VL, six-membered) and e-CL (seven-membered), were each polymerized via the action of a lipase from Candida cylindracea (hpase CC), hpases BC and PF, and a porcine pancreatic hpase (PPL) [83,84]. Later, a variety of cychc esters with different ring sizes and structures were also polymerized via a hpase-mediated catalysis. 

Kurcok R, Matuszowicz A., Jedlinski Z., Kricheldorf H.R., Dubois R, Jerome R., Substituent effect in anionic polymerization of b-lactones initiated by alkali metal alkoxides, Macromol. Rapid Commun., 16,1995, 513-519. 

Appropriate macrodiols are produced via ring opening polymerization of cyclic diesters or lactones initialized by low molecular weight diols (see Fig. 16.4). The sequence structure of cooligomers can be influenced by application of a transesterification catalyst. The molecular weight of the oligomers can be controlled by the monomer/initiator ratio. Typically, the molecular masses Mn being obtained are between 500 g mol and 10 000 g mol T The net... 

LIVING POLYMERIZATION OF p-LACTONE INITIATED WITH ALUMINUM PORPHYRIN. MOLECULAR DESIGN OF HIGHLY ACTIVE INITIATING SYSTEM... 

Important progress was also observed in the anionic polymerization of P-lactones initiated by strong bases such as alkali metal alcoholates. As described... 

The reaction of perfluoroalkyl iodides with alkenes affords the perfluoro-alkylated alkyl iodides 931. Q.a-Difluoro-functionalized phosphonates are prepared by the addition of the iododifluoromethylphosphonate (932) at room temperature[778], A one-electron transfer-initiated radical mechanism has been proposed for the addition reaction. Addition to alkynes affords 1-perfluoro-alkyl-2-iodoalkenes (933)[779-781]. The fluorine-containing oxirane 934 is obtained by the reaction of allyl aicohol[782]. Under a CO atmosphere, the carbocarbonylation of the alkenol 935 and the alkynol 937 takes place with perfluoroalkyl iodides to give the fluorine-containing lactones 936 and 938[783]. 

Alkoxide-Type Initiators. Using the guide that an appropriate initiator should have approximately the same stmcture and reactivity as the propagating anionic species (see Table 1), alkoxide, thioalkoxide, carboxylate, and sUanolate salts would be expected to be usehil initiators for the anionic polymeri2ation of epoxides, thikanes, lactones, and sUoxanes, respectively (106—108). Thus low molecular weight poly(ethylene oxide) can be prepared... 

Reaction between butadiene and CO2 has been extensively studied (171) since the reaction was first demonstrated (167—170). This reaction has been shown to be catalyzed by Pd (172,173), Ni (174), Ru (175), Pt (178), and Rh (172,173) catalysts. Products include gamma (5) and delta lactones (6), acids (7,8), and esters (9). Mechanistic studies have shown that butadiene initially forms a dimer (Pd, Ru, Ni) or trimer (Rh) intermediate followed by CO2 insertion (171). The fate of these intermediates depends on the metal, the ligands, and the reaction conditions. 

Ring opening of a lactone, e.g. of e-caprolactone with dihydroxy or trihydroxy initiators ... 

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