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DOI: 10.1055/s-2008-1032048
Dimethyl Carbonate (DMC): A Versatile and Environmentally Benign Building Block
Dedicated to Prof. Asit K. Chakraborti
Publication History
Publication Date:
12 February 2008 (online)
Biographical Sketches
Introduction
Dimethyl carbonate (DMC) is a unique molecule with versatile chemical reactivity. In many aspects, DMC is an environmentally benign building block [1] because of its cheap commercial availablility and high ecological safety profile; it possesses interesting solvating properties, low toxicity, and is highly biodegradable. [2]
Preparation
Originally, DMC was synthesized in a clean process of catalytic oxidative carbonylation of methanol in the presence of oxygen. [3] Very recently, DMC was efficiently synthesized from methanol, propylene oxide, and CO2, catalyzed by recyclable organic/inorganic bases (Scheme [1] ).
The versatile role of DMC as solvent, [4] methoxycarbonylation agent, [5] esterification [6] and transesterification agent, [7] green oxidiant [8] and selective methylating agent [9-12] is summarized below.
Abstract
(A) Solvent: Environmentally friendly oxidations of various organic compounds with the H2O2/methyltrioxorhenium (MeReO3, 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 days at room temperature. [4] | |
(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. | |
(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 advantages, niches, and upscalability. [6] | |
(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] | |
(E) Oxidant: In the remarkable reactions where DMC behaves as an oxidant cyclic ketones are transformed into α,ω-dimethyl esters [8] 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 (K2CO3) to yield adipic and pimelic methyl (or ethyl) esters, respectively. | |
(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/BAL2 sequence. Moreover, DMC also serves as solvent. Methylation with DMC is often very selective and N-methylation of anilines is another example. | |
(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] | |
(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] |
- 1
Tundo P.Selva M. Acc. Chem. Res. 2002, 35: 706 - 2
Romano U,Rivetti F, andDi Muzio N. inventors; US Patent 4,318,862, 95. ; Chem. Abstr. 1981,80141w - 3
Tian J.-S.Miao C.-X.Wang J.-Q.Cai F.Du Y.Zhao Y.He L.-N. Green Chem. 2007, 9: 566 - 4
Bernini R.Mincione E.Barontini M.Crisante F.Fabrizic G.Gambacortad A. Tetrahedron 2007, 63: 6895 - 5
Sima T.Guo S.Shi F.Deng Y. Tetrahedron Lett. 2002, 43: 8145 - 6
Shieh W.-C.Dell S.Repi O. Tetrahedron Lett. 2002, 43: 5607 - 7
Gong J.Ma X.Wang S. Appl. Catal., A 2007, 316: 1 - 8
Selva M.Marques CA.Tundo P. Gazz. Chim. Ital. 1993, 123: 515 - 9
Selva M. Synthesis 2003, 2872 - 10
Marques CA.Selva M.Tundo P.Montanari F. J. Org. Chem. 1993, 58: 5765 - 11
Jyothi TM.Raja T.Talawar MB.Rao BS. Appl. Catal., A 2001, 211: 41 -
12a
Selva M.Marques CA.Tundo P. J. Chem. Soc., Perkin Trans. 1 1994, 1323 -
12b
Loosen P,Tundo P, andSelva M. inventors; US Patent 5,278,533. - 13
Trost BM. Science 1991, 254: 1471
References
- 1
Tundo P.Selva M. Acc. Chem. Res. 2002, 35: 706 - 2
Romano U,Rivetti F, andDi Muzio N. inventors; US Patent 4,318,862, 95. ; Chem. Abstr. 1981,80141w - 3
Tian J.-S.Miao C.-X.Wang J.-Q.Cai F.Du Y.Zhao Y.He L.-N. Green Chem. 2007, 9: 566 - 4
Bernini R.Mincione E.Barontini M.Crisante F.Fabrizic G.Gambacortad A. Tetrahedron 2007, 63: 6895 - 5
Sima T.Guo S.Shi F.Deng Y. Tetrahedron Lett. 2002, 43: 8145 - 6
Shieh W.-C.Dell S.Repi O. Tetrahedron Lett. 2002, 43: 5607 - 7
Gong J.Ma X.Wang S. Appl. Catal., A 2007, 316: 1 - 8
Selva M.Marques CA.Tundo P. Gazz. Chim. Ital. 1993, 123: 515 - 9
Selva M. Synthesis 2003, 2872 - 10
Marques CA.Selva M.Tundo P.Montanari F. J. Org. Chem. 1993, 58: 5765 - 11
Jyothi TM.Raja T.Talawar MB.Rao BS. Appl. Catal., A 2001, 211: 41 -
12a
Selva M.Marques CA.Tundo P. J. Chem. Soc., Perkin Trans. 1 1994, 1323 -
12b
Loosen P,Tundo P, andSelva M. inventors; US Patent 5,278,533. - 13
Trost BM. Science 1991, 254: 1471