A-Methyl-P-propiolactone

Liu X-Q, Wang M-X, Li Z-C, Li F-M (1999) Synthesis and ring-opening polymerization of a-chloromethyl-a-methyl-P-propiolactone. Macromol Chem Phys 200 468 73... 

Svirkin, Y. Y., Xu, J., Gross, R. A., Kaplan, D. L., and Swift, G., Enzyme-catalyzed stereoelective ring-opening polymerization of a-methyl-P-propiolactone, Macromolecules, 29, 4591 597, 1996. 

Van Buijtenen and coworkers [98] demonstrated Novozym 435-catalyzed ringopening of a range of a-methylated lactones (a-methyl-P-propiolactone (3-MePL ... 

Four-membered ring lactones 3-propiolactone (P-PL) [68-70], P-butyrolactone (P-BL) [71-76], benzyl P-malolactonate (BBM) [77] and a-methyl-P-propiolactone (MPL) [78, 79] were polymerised using different lipases (Table 12.5). 

Varying the substitution of the P-Iactone, by using racemic a-ethyl-a-methyl-P-propiolactone or a-propyl-a-methyl-P-propiolactone, led to the production of an optically active polymer which obeyed stereoselection in the presence of a diethylzinc/(R)-(-)-3,3-dimethyl-l,2-butanediol catalytic system, whereas the diethylzinc/methanol system led only to atactic polymers [56-58]. These findings indicated that the enantiomorphic sites of the zinc coordination catalyst were unable to recognize the chirality of the lactone monomer used for the polymerization. It should also be noted here that an antisteric type of steroselection in the polymerization of racemic a-propyl-a-methyl-P-propiolactone was reported when dimethylcadminium/(R)-(-)-3,3-dimethyl-l,2-butanediol was used as catalyst [56]. 

In addition to BL, the lipase-catalyzed ROP of substituted four-membered lactones such as P-methyl-P-propiolactone and P-propiolactone was first reported by Nobes et al [84], followed by several studies with ( )-a-methyl-P-propiolactone [85], a-decenyl-P-propiolactone, a-dodecyl-P-propiolactone [86], and benzyl-P-D,L-malolactonate, among others [87]. 

Gross and coworkers prepared enantioenriched poly((R)-a-methyl- 3-propiolactone), making use of the selectivity of lipases. Initially, (R)-a-methyl-P-propiolactone (a-Me-P-PL Scheme 15.1) was isolated via a lipase-catalyzed kinetic... 

The Potassium complex of I8-Crown-6 or Potassium Naph-thalenide effects ring-opening to give acetates or their alkylated derivatives in good yield (eq 3). Treatment of the reaction mixture obtained from p-methyl-p-propiolactone and potassium-18-crown-6 with hydrochloric acid or alkyl halides gives the acetate (S) or its alkylated derivative (6), respectively. The a,3-unsaturated carboxylic acid (7) or its ester (8) is formed by the action of the potassium naphthalenide-18-crown-6 complex. ... 

An enantioselective polymerization of four-mem-bered lactones was demonstrated. Racemic a-methyl-/3-propiolactone was stereoselectively polymerized by Pseudomonas cepacia lipase (lipase PC) to give an optically active (S)-enriched polyester with enantiomeric excess (ee) of 50%.154 From racemic /3-BL, (P)-enriched PHB with 20—37% ee was formed by using thermophilic lipase as catalyst.155... 

Various substituted lactones were used for enzymatic polyester synthesis via ROP ( )-a-methyl- 3-propiolactone [101], P-methyl-P-propiolactone [78], a-decenyl-P-propiolactone [27], a-dodecenyl-P-propiolactone [46],benzyl-P-D,L-malonolactonate [104], a-methyl-e-caprolactone [96], oc-methyl-8-valerolactone [96], l,4-dioxane-2-one [91], and others (see also Table 4.2). 

ROP of substituted 4-membered P-propiolactones, (P-PL), were reported using lipase-catalysis in bulk. oc-methyl-P-PL gave a polymer with an analogous structure to poly(lactic acid) (PLA). Pseudomonas fluorescent lipase-catalyzed ROP of a-methyl-P-PL in toluene was found to be selective for (S)- a-methyl-P-PL giving (S) enriched poly(oc-methyl-P-PL) with M ranging from 2000 to 2900 [101]. 

The P-substitution stabilizes cation II and increases the proportion of the O-acyl cleavage. Lando et al.19 Z0) have found that the optical activity of poly (D- + -P-methyl-P-propiolactone) is lower than that of the monomer, indicating a simultaneous inversion (route I) and retention (II) at the P-C-4 atom. 

Knunyants, I.L. Cheburkov, Y.A. Fluorine containing 3-lactones. I. P,P-Bis(trifluoro-methyl)-P-propiolactone and its properties. Izv. Akad. Nauk SSSR, Ser. Khim. 1960, 678-685. 

As a consequence of the a to P transition which accompanies orientation, fibre patterns of the a-form are difficult to obtain. Melt extruded fibres of poly(a,a-dimethyl-P-propiolactone), known as poly(pivalolactone) (PPL), do, however, crystallize in the a-form and retain their orientation upon high temperature annealing under tension . Furthermore, oriented samples of poly(a-methyl-a-n-propyl-B-propiolactone) (PMPPL) have been prepared which show x-ray layer lines corresponding to the two phases. The a-form of both PPL and PMPPL is characterized by a fibre repeat distance of about 6 A, which has been identified as the periodicity of a 2j helix. Although oriented samples of poly(a-methyl-a-ethyl-B-propiolactone) (PMEPL) in the a-phase have never been reported, x-ray powder data have been fitted with a monoclinic unit cell with c = 6.1 A. 

These steps repeat themselves until the chains are built up. Anionic polymerizations can yield optically active polymers. This was observed in formations of poly(a-methyl, a-ethyl-p-propiolactone) [193] that contains asymmetric carbon atoms. 

Optically active lactones are valuable building blocks in organic synthesis (4) and in the preparation of optically active biodegradable polymers (7,5). Several chemical methods for producing these compounds and their corresponding polymers have been explored (6) but unfortunately all of these methods are either experimentally cumbersome or afford the lactones with only modest enantioselectivities. Examples of chemically prepared optically active polyesters include poly(a-phenyl-P-propiolactone) (7), poly(a-ethy(-a-phenyl-P -propiolactone) (S, 9), poly(a-methyl-a-ethyl-P-propiolactone) (70) and poly(lactic acid) (77, 72). Use of enantioselective polymerization catalysts to carry out stereoelective polymerizations of racemic lactones has produced mixed results. For example, stereoelective polymerization of [/ ,S]- P-methyl-P-propiolactone with a catalyst from Zn ( 2115)2 and [7 ]-(-)-3,3-dimethyl-l,2-butanediol showed only a small enantiomeric enrichment in the final polymer (75). Stereoselective copolymerizations of racemic (LL/DD monomers) and meso (LD monomer) lactides using chiral catalyst that gives heterotactic and syndiotactic PLA, respectively have also been studied (77). 

P-Hydroxy acids lose water, especially in the presence of an acid catalyst, to give a,P-unsaturated acids, and frequendy P,y-unsaturated acids. P-Hydroxy acids do not form lactones readily because of the difficulty of four-membered ring formation. The simplest P-lactone, P-propiolactone, can be made from ketene and formaldehyde in the presence of methyl borate but not from P-hydroxypropionic acid. P-Propiolactone [57-57-8] is a usehil intermediate for organic synthesis but caution should be exercised when handling this lactone because it is a known carcinogen. 

Hydracrylic acid, see p-Propiolactone Hydrazobenzene, see Aniline Hydriodic acid, see Methyl iodide Hydrobromic acid, see Bromodichloromethane, Bromoform, Methyl bromide, Metobromuron Hydrochloric acid, see Alachlor. Aldrin, Benzyl chloride, a-BHC, p-BHC, Bis (2-chloroethyl) ether, Bis(2-chloroisopropyl) ether, Bromacil. Bromodichloromethane, Carbon tetrachloride, Chloroethane, Chloroform, o-Chloronitrobenzene. Chloropicrin, Chloroprene, p-Chloronitrobenzene, 2,4-D, see Dalanon-sodium. p.p -DDD, p,p -DDT, Dicamba. 1,1-Dichloroethane, 1,1-Dichloroethylene, fratts-l,2-Dichloroethylene, s/m-Dichloromethyl ether, 2.3-Dichloronitrobenzene. 3.4-Dichloronitrobenzene. 1,2-Dichloropropane, cis-1,3-... 

New substrates. Useful chiral intermediates that are now available from resolution by lipases are P-chlorodifluoromethyl-P-propiolactone," P-methyl-a- methylenepropiolactone, ... 

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