US EPA

7480361 

Journal Article 

Dimethyl carbonate (DMC): A versatile and environmentally benign building block 

Chankeshwara, SV 

2008 

1 

Synlett
ISSN: 0936-5214
EISSN: 1437-2096 

4 

624-625 

English 

10.1055/s-2008-1032048 

(A) Solvent: Environmentally friendly oxidations of various organic compounds with the H2O2/methyltrioxorhenium (MeReO 3, MTO) catalytic system have been performed in dimethyl carbonate as solvent. Oxidations proceeded with good conversions and in good yields. Spectrophotometric analysis demonstrated that the [MeReO(O-O)2] complex was formed in dimethyl carbonate and that it was stable for several davs at room temperature.4 (Chemical Equation Presented) (B) N-Methoxycarbonylation Agent: Primary and secondary aliphatic amines could react with DMC using ionic liquids as solvent and catalyst to give alkyl carbamates in good yields.5 The desired solid carbamate could be recovered by simple filtration from the two-layer mixture of DMC and ionic liquid. The formation of N-methylated and deammoniated products was restrained. (Chemical Equation Presented) (C) Esterification Agent: An environmentally friendly process for the esterification of carboxylic acids with DMC can be accelerated (20-480-fold) by employing a combined strategy of microwave and using DBU as the catalyst. This approach provides synthetic advan tages, niches, and upscalability.6 (Chemical Equation Presented) (D) Trans-Esterification/Disproportionation Reaction: Diphenyl carbonate (DPC) is considered a substitute for phosgene to synthesize polycarbonate resins. Trans-esterification of DMC with phenol in the presence of titanocene and other titanium complexes yields methyl phenyl carbonate (MPC), which gives DPC by further trans-esterification with DMC or the disproportionation.7 (Chemical Equation Presented) (E) Oxidant: In the remarkable reactions where DMC behaves as an oxidant cyclic ketones are transformed into αω- dimethyl esters8 with an atom efficiency of 1.0. 13 DMC has a potential as valuable green oxidant for industrial application in reaction of cyclopentanone and cyclohexanone with DMC (or DEC) and a base (K 2CO3) to yield adipic and pimelic methyl (or ethyl) esters, respectively. (Chemical Equation Presented) (F) N-Methylating Agent: At 130-150 °C and in the presence of K2CO3, o-aminophenol (1)9 and oximes (2)10 readily react with dimethyl carbonates to give the corresponding N-methylbenzoxazol-2-ones in high yields. This reaction is a rare example where dialkyl carbonates may simultaneously act as carbonylating and alkylating agents likely via a BAC2/B AL2 sequence. Moreover, DMC also serves as solvent. Methylation with DMC is often very selective and N-methylation of anilines is another example. (Chemical Equation Presented) (G) O-Methylating Agent: DMC is a safe substitute for dimethyl sulfate or methyl halides. These conventional methylating agents are toxic and corrosive and give a stoichiometric amount of inorganic byproducts. Methylation of catechol with DMC as an alkylating agent has been carried out over calcined Mg-Al hydrotalcites with O-selectivity of 96.1 % with a guaiacol selectivity of 84%.11 (Chemical Equation Presented) (H) C-Methylating Agent: The most interesting and well-studied reaction, particularly in view of its selectivity, is the mono-C-methylation of arylacetonitriles and methyl arylacetates to produce monomethylated 2-arylpropionitriles and methyl 2-arylpropionates, respectively, with a selectivity of >99.5%. Further, DMC also proved to be the best solvent for such reactions. This reaction is interesting in view of the synthesis of anti-inflammatory drugs.12 (Chemical Equation Presented) © Georg Thieme Verlag Stuttgart. 

carbonic acid derivative; dimethylcarbonate; methanol; oxidizing agent; oxygen; propylene oxide; solvent; unclassified drug; article; carbonylation; catalysis; chemical reaction; esterification; oxidation; synthesis; transesterification