Alkylene carbonate synthesis

The first reports describing the formation of cyclic carbonates (CCs) appeared during the early 1930s [99, 100], whilst the first patents (essentially related to the synthesis of ethene and propene carbonates) appeared more than 50 years ago [101, 102]. The Huntsman Corporation is one the world s largest producers of alkylene carbonates, with a capacity of 33 kt per year, covering approximately 50% of CC production worldwide. Today, CCs are widely used in the manufacture of... 

Therefore, any possible use of DMC as substitute of phosgene should be based on a different synthesis of DMC, not involving phosgene. Non-phosgene alternative routes for DMC production, basically, have relied on the reaction of methanol with carbon monoxide (oxidative carbonylation) or with carbon dioxide (direct carboxyl-ation with CO2, or indirect carboxylation, using urea or alkylene carbonates as CO2 carriers) (Figure 1.10) [72]. 

Another carbon dioxide insertion reaction is observed with Al (TPP)(OMe) This compound readily and reversibly traps carbon dioxide at room temperature in the presence of 1-methylimidazole. The trapped carbon dioxide is sufficiently activated to react with an epoxide at room temperature, thus producing the corresponding alkylcarbonate. As illustrated in Scheme 11, the cyclic carbonate is considered to be formed - at least partly - by nucleophilic attack on a linear intermediate. Thus the alkoxide aluminum porphyrin-methylimidazole system would be a good catalyst for synthesis of alkylene carbonates from carbon dioxide and epoxides under mild conditions. 

Synthesis involves the formation of apoly(alkylene carbonate) prepolymer formed from intermediates of organic carbonate moieties by reaction of a diol and organic carbonate monomer at elevated temperatures in the presence of a catalyst such as stannous octoate. Diols include 1,6-hexanediol, 1,4-butanediol and 1,8-octanediol, wi hile carbonates include diphenyl carbonate and dibutyl carbonate. p-Dioxanone is then added to form the poly(p-dioxanone-co-alkylene carbonate) copolymer. 

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. 

Vinyl-functional alkylene carbonates, useful in the preparation of polymers that contain alkylene carbonate pendant groups, can also be prepared from GC. Two examples are the reaction of GC with maleic anhydride and acryloyl chloride to produce the acrylate-functional cyclic carbonates (3 and 4, respectively. Scheme 24). Although the transesterification of alkyl esters such as dimethyl maleate or methyl acrylate by reaction with GC represents an obvious means of obtaining the above materials, the temperatures required of such processes (>100°C) result in unwanted polymerization of both the reactant and product species, even in the presence of well-known radical inhibitors such as 2,6-di-tert-butyl-p-cresol or phenothiazine. In addition, the synthesis of vinyl-functional alkylene carbonates is greatly complicated by the fact that such materials cannot be purified by distillation and must be stored at temperatures < 0 ° C in the presence of a... 

Alkylene CCs have been prepared through the transesterification of appropriate glycols with dialkyl carbonates (usually diethyl or dimethyl carbonate) in the presence of a suitable catalyst. One of the first such examples was the synthesis of six-membered CCs by the transesterification of propane-1,3-diols with DEC catalyzed by sodium ethanolate (Equation 7.31) [289], The reaction was carried out at temperatures between 293 and 333 K, and a conversion yield of 40% was obtained. 

The reaction of carbon disulfide with 1,2-alkylene diamines (I) yields N-(2-aminoethyl) dithiocarbamic acids (II) which split off hydrogen sulfide thermally to give imidazolidine-2-thiones (III) (Hofmann-process). The simplest example, the reaction of carbon disulfide with ethylenediamine, is described in Organic Synthesis (5). The reaction is general for N,N -dialkyl-, N,N -diaryI, as well as for N,N -bis-(arylakyl) ethylene diamines. The rate of reaction is determined by the basicity of the diamine. Electron-donor substituents in the para-position of N-aromatically substituted ethylene diamines accelerate dithiocarbamate formation electron-acceptor groups retard it. 

Oxazolidinones are useful heterocyclic compounds in organic synthesis. They have a wide range of applications in asymmetric syntheses as chiral reagents and, since they have good antibacterial properties, in medicinal chemistry [53]. Oxazolidinones can be synthesized in traditional solvents such as acetonitrile [54] or DMF [5 5], but it is more environmentally friendly to use scC02 [56]. In the reaction an internal propargyl alcohol, carbon dioxide, and a primary amine participate in a cycloaddition reaction under supercritical conditions to give 4-alkylene-l,3-oxazoli-din-2-ones (Equation 4.30). 

In 1978 we reported the synthesis of poly(amide enamlnes) by the reaction of a diamine with diketene in aprotic solvents. The reaction proceeds via the formation of acetacetoamides which condense further with the amines giving the poly(amide enamines), 2 Pol)nners derived from alkylene diamines with four to twelve carbons were found to be biodegradable, supporting the... 

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. 

---