Carbonylating agent

The oxidative carbonylation of alcohols and phenols to carbonates can be catalyzed by palladium or copper species [154-213]. This reaction is of particular practical importance, since it can be developed into an industrial process for the phosgene-free synthesis of dimethyl carbonate (DMC) and diphenyl carbonate (DPC), which are important industrial intermediates for the production of polycarbonates. Moreover, DMC can be used as an eco-friendly methylation and carbonylation agent [214,215]. The industrial production of DMC by oxidative carbonylation of methanol has been achieved by Enichem [216] and Ube [217]. 

H. Komura, T. Yoshino, and Y. Ishido, Preparation of cyclic carbonates of sugar derivatives with some carbonylating agents, Carbohydr. Res, 40 (1975) 391-395. 

The metal complex used was Ni(GO)4 under a carbon monoxide atmosphere in DMF at 50 °C for 3h. A suitable temperature was found to be in the range 70-90 °C and the optimum reaction time was 1-3 h. Under an inert nitrogen atmosphere the yield was reduced drastically since the CO atmosphere is essential for the reaction. The use of THF instead of dimethylformamide (DMF) led to a reduction of the yield. Similarly, when 0.1 equiv of Ni(CO)4 was used as a catalytic metal carbonylating agent, instead of 1 equiv, a low yield of the product was noted. The use of metal carbonyls such as Fe(CO)s, W(CO)s led to a negligible amount of diazetidinediones (Scheme 49). 

Af,Af/-Carbonyldiimidazole (CDI) is a highly reactive carbonylating agent that is used for activation of carboxyl or hydroxyl groups for conjugation to amines... 

A very interesting deoxygenation reaction, in which carbon monoxide serves as both, a deoxygenating agent as well as a carbonylating agent, was found recently by Bhaduri et al. The formation of phenyl isocyanate from nitrobenzene with carbon monoxide is catalyzed by trinuclear ruthenium clusters such as Ru3(CO),2 or [HRu3(CO) ] ... 

Phosgene is a particularly useful carbonylating agent, but even here it is not unique in its ability to effect carbonylation reactions. In particular, ethyl chloroformate has been described for its suitability as a ring-closing reagent in the synthesis of imidazoline derivatives [786] ... 

Unlike phosgene, however, the use of carbonyl difluoride as a carbonylating agent is... 

Dimethylcarbonate is sparingly soluble in water and miscible with the most organic solvent, particularly polar solvents such as esters, ketones, ethers, and alcohols. Dimethylcarbonate is extremely stable to pyrolysis up to at least 623 K. Dimethylcarbonate undergoes base-or acid-catalyzed hydrolysis to produce methanol and carbon dioxide. One of the most important properties of DMC is low toxicity compared with conventional methylating agents or carbonylation agents. Table 1 summarizes the physical and toxicological properties of DMC. 

Phosgene produced by chlorinating carbon monoxide is used as a carbonylating agent to convert amines to isocyanates, as shown by reactions (8) and (9). Thus, the reaction of phosgene with diphenylmethane diamine results in the formation of methylene diphenyl diisocyanate (MDI), and with toluenediamine to form toluene diisocyanate (TDI). The isocyanates are used to produce polyurethanes for flexible and rigid foams, elastomers, coatings, and adhesives, for the construction and automotive industries. 

Polycarbonate resins, formed by using phosgene as a carbonylating agent for bisphenol A (Eq. 21), are used in automotive parts, appliances, power tools, and glazing, among many other applications. 

---