8-Propiolactones, 6-substituted

For example, polymers from monoalkyloxiranes and thiiranes, 1- (or 4)-monosubstituted butadienes, ot-substituted- 3-propiolactones, ot-amino acids, and so on. 

More recently Teyssie determined the rate constants in the polymerization of e-caprolactone (eCL) initiated with aluminium alkoxides, believing that the covalent species are the only ones responsible for propagation [4]. For the same monomer Yamashita estimated tentatively rate coefficients of propagation using an anionic initiator [ ]. Lenz in his studies of substituted g-propiolactones (gPL) observed peculiar influence of structure on reactivity that can have its origin in the multiplicity of ionic structures involved [fi]. 

Reaction with propiolactone. The reaction of organocuprates with /Tpropio-lactone can be used to prepare -substituted propionic acids. 

Oxo-3,4-dihydro-2//-pyrido[l,2-a]pyrimidines (142) may easily be converted (e.g., by heating in water) to the betaines (143)200,204 The latter can also be prepared from 2-aminopyridines with propiolactone,206 acrylic acid,18 3-substituted propionitriles, and other acrylic acid derivatives.207,208 The betaines (143) revert to the bicyclic compounds (142) upon heating in acid 200 204-206-207... 

Substituted /3-propiolactones, easily available in chiral form, undergo similar ring-opening reactions under these conditions, thus offering an alternative to enantioselective 1,4-addition (Scheme 39).105... 

Most of the reactions of /3-lsctonee in the literature concern propiolactone itself. Since there is an undentandabie tendency to consider these reactions cf propiolactone as general reactions, one must bear in mind in working with substituted -lactones tiiat substituents can exert a profound influence, not only on the reaction rate, but sometimes even on the natiirc of the reactionB.m As the reactivity of the ketene dimers with a -lactone structure differs from that of the other lactones, they are treated separately in section Vn,... 

In anionic polymerization, B-propiolactone initiated with potassium alcoholate, gives,in initiation,both alco-holate and carboxylate anions. Alcoholate ions in every next step convert partially into carboxylate whereas carboxylate reproduce themselves quantitatively. Thus, after a few steps only carboxylate anions are left (14). Related situation was observed in the polymerization of styrene oxide (15). Here, however, it is only due to the structure of the initiator used. Thus, when in the initiation step both secondary and primary alcoholate anions are formed, due to the low steric requirements, in the next step apparently only the attack on the least substituted carbon atom takes place and already in the second step exclusively secondary alcoholate anions are present. 

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]. 

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