Scheme 4.2 Methylation and methoxycarbonylation using DMC.
Since 1980, with the development of gas liquid phase transfer catalysis (GL-PTC) as a continuous-flow (CF) method for organic syntheses,5 our group has had a long-standing interest in the use of DMC as an environmentally friendly substitute for DMS and CH3X in methylation reactions, and for phosgene in methoxycarbonylation reactions (Scheme 4.2). Among the specific advantages of DMC, and of alkyl carbonates in general, is that their building block is CO2, an environmentally benign compound, which does not cause emissions of volatile organic compounds (VOC) in the atmosphere.
This chapter reports on the reactivity of organic carbonates as alkylating agents, with emphasis on the lightest term of the series, DMC. Under both CF and batch conditions, DMC can react with a number of nucleophilic substrates such as phenols, primary amines, sulfones, thiols, and methylene-active derivatives of aryl and aroxy-acetic acids. The mechanistic and synthetic aspects of these processes will be elucidated.
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