Alkylene five-membered

The transesterification of 1,2-diols by reaction with carbonates, both cyclic and linear, produces five-membered alkylene carbonates almost exclusively. A well-known example of this is the reaction of DMC with propene glycol to yield PC [295],... 

Copolymerisation of propylene oxide as well as other oxiranes with carbon dioxide in the presence of zinc-based coordination catalysts is generally accompanied with the formation of a cyclic five-membered carbonate, propylene carbonate or another alkylene carbonate [147,206,207,210,212,230]. The alky-lene carbonate, however, is not the precursor for poly(alkylene carbonate), since it hardly undergoes a polymerisation under the given conditions [142-146],... 

Reaction of asymmetric (2-butene-l,4-diyl)magnesium with a,to-alkylene dihalides usually gives two isomeric products. For example, treatment of (2-phenyl-2-butene-l,4-diyl)magnesium with 1,3-dibromopropane at — 78°C, followed by warming to room temperature, resulted in the generation of two five-membered carbocycles, 1-phenyl-1-ethenylcyclopentane and a-cyclopentylstyrene, with a ratio of 77 23, in a 76% isolated yield. 

In contrast with the general 1,2-cyclizations of symmetric (2-butene-l,4-diyl)magnesium complexes with a,a>-alkylene dihalides, reactions of both symmetric and asymmetric (2-butene-l,4-diyl)magnesium complexes with diorganosilyl dichlorides yield exclusively overall 1,4-additions, generating silicon-containing five-membered rings. Some of these results are summarized in Table 5. 

Carbon monoxide is an important industrial C-1 Chemicar. The major derived products are methanol and phosgene. The synthesis of methyl methacrylate from acetylene, carbon monoxide and methanol is another industrially useful reaction. Carbon monoxide is a stable carbene, CO, and therefore I have included many of its cycloaddition reactions. The [2-I-2-I-1] cycloaddition reaction which leads to five-membered ring carbonyl compounds is of considerable synthetic value. Copolymers of alkenes and carbon monoxide are a new class of biodegradable polyketones, which can be readily converted into functional polymers. Also copolymers of alkylene oxides and carbon monoxide are known. 

The synthesis of five-membered alkylene carbonates (1,3-dioxolan-2-ones) of the structure presented in Scheme 1 has been the subject of considerable research. Two of them, ethylene carbonate (EC) (R = H) and propylene carbonate (PC) (R = H, R" = CH3), have been available commercially for over 45 years. 

The alkylene carbonates are easily available through transesterification of dialkyl carbonates (usually dimethyl or diethyl carbonate) or diphenyl carbonate with appropriate 1,2-diols in the presence of alkaline catalysts.This approach for the preparation of five-membered cyclic carbonates also was described in the 1950s by Ludwig and Piech ° and Sarel et al ... 

Vinyl-functional alkylene carbonates can also be prepared from the corresponding epoxides in a manner similar to the commercial manufacture of ethylene and PCs via CO2 insertion. The most notable examples of this technology are the syntheses of 4-vinyl-1,3-dioxolan-2-one (vinyl ethylene carbonate, VEC) (5, Scheme 24) from 3,4-epoxy-1-butene or 4-phenyl-5-vinyl-l,3-dioxolan-2-one (6, Scheme 24) from analogous aromatic derivative l-phenyl-2-vinyl oxirane. Although the homopolymerization of both vinyl monomers produced polymers in relatively low yield, copolymerizations effectively provided cyclic carbonate-containing copolymers. It was found that VEC can be copolymerized with readily available vinyl monomers, such as styrene, alkyl acrylates and methacrylates, and vinyl esters.With the exception of styrene, the authors found that VEC will undergo free-radical solution or emulsion copolymerization to produce polymeric species with a pendant five-membered alkylene carbonate functionality that can be further cross-linked by reaction with amines. Polymerizations of 4-phenyl-5-vinyl-l,3-dioxolan-2-one also provided cyclic carbonate-containing copolymers. 

With all six series of polyester illustrated in Figure 25.14, as the number of methylene groups in the repeating unit increases so the polymer becomes more like a linear polyethylene (polymethylene). Thus the melting points for five of the six classes are seen to converge towards that of the melting point of polymethylene. In the ca.se of the sixth class, the poly(alkylene adipates), there would appear no reason to believe that additional data on other specific members of the class would not lead to a similar conclusion. 

Polyethers are prepared by the ring opening polymerization of three, four, five, seven, and higher member cyclic ethers. Polyalkylene oxides from ethylene or propylene oxide and from epichlorohydrin are the most common commercial materials. They seem to be the most reactive alkylene oxides and can be polymerized by cationic, anionic, and coordinated nucleophilic mechanisms. For example, ethylene oxide is polymerized by an alkaline catalyst to generate a living polymer in Figure 1.1. Upon addition of a second alkylene oxide monomer, it is possible to produce a block copolymer (Fig. 1.2). 

Although the cyclic selenohydrocarbons having five- or six-membered rings are isolated in good yield by the interaction of alkylene dibromides and sodium selenide, trimethylene dibromide and sodium selenide furnish only a small yield of c cZoselenopropane,... 

E E. Bailey, Jr., is a Senior Research Scientist at Union Carbide Chemicals and Plastics Company Inc., in South Charleston, West Virginia. He is the coauthor or coeditor of five books and 68 journal articles and book chapters, and holds 50 U.S. patents on polymer syntheses and processes. Dr. Bailey is a Fellow of the American Institute of Chemists, American Association for the Advancement of Science, and New York Academy of Sciences, a member of the American Physical Society and Society of Rheology, and a Director of the American Chemical Society. In 1987, he was given the American Institute of Chemists Chemical Pioneer Award for his work on poly(alkylene oxides). Dr. Bailey received the A-B. (1948) degree from Amherst College, Amherst, Massachusetts, and M.S. (1950) and Ph.D. (1952) degrees from Yale University, New Haven, Connecticut. 

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