Diesters, dimethyl carbonate reactions

The ene-yne CM of fatty acid-derived terminal alkenes with several alkyne derivatives was shown by Bruneau et al. [75], These reactions, which led to renewable conjugated dienes, were performed in a one-pot two-step procedure. In the first step, the ethenolysis of methyl oleate was performed in the presence of the first-generation Hoveyda-Grubbs catalyst (2.5 mol%) using dimethyl carbonate as solvent at room temperature. After completion of the ethenolysis (90% conversion), C4 (1 mol%) and the corresponding alkyne (0.5 equivalents with respect to olefins) were added and the reaction was run at 40°C for 2 h (Scheme 9). The desired dienes were thus obtained in high yields close to the maximum theoretical value (50%). Moreover, in order to maximize the formation of functional dienes, the same reaction sequence was applied to the diester obtained by SM of methyl oleate. In this way, the yield of functional dienes was increased up to 90% depending on the... 

Dimethyl carbonate is a diester. Use your knowledge of the Grignard reaction to work your way through this problem. 

Carbonic add diesters are very attractive reagents and of great economic interest because they represent safe, nonenvironmentally acceptable alternatives to phosgene for carbonylation and carboxylation reactions. For example, methoxycarboxylation with dimethyl carbonate offers an eco-friendly alternative route for the production of carbamates and isocyanates, which are valuable precursors of ureas (see Sections 4.3.1 and 4.3.2) [781, 782]. The method is comparable, from an environmental point of view, with the transition metal catalyzed carbonylation of nitro compounds and amines with CO. 

Starch carbonate diesters were formed by reaction of starch with alkylene carbonates under diminished pressure at 100-140 °C 2002 The products were proposed as surgical dusting powders. Another method involved dimethyl sulfoxide as the reaction medium, triethylamine as the catalyst, and trans-carbonates of glycosides as the acylating agents. Thionocarbonates were used similarly. The degree of substitution was O.4.2003 Another method involves 1-acyl I, I -carbodiirnidazole or dicarboxylic acid imidazolides at pH 8.O.2004... 

The polycondensation of a diol and the diester of a dicarboxylic acid (e.g., the dimethyl ester) can be carried out in the melt at a considerably lower temperature than for the corresponding reaction of the free acid. Under the influence of acidic or basic catalysts a transesterification occurs with the elimination of the readily volatile alcohol (see Example 4.3). Instead of diesters of carboxylic acids one can also use their dicarboxylic acid chlorides, for example, in the synthesis of high-melting aromatic polyesters from terephthaloyl dichloride and bisphenols. The commercially very important polycarbonates are obtained from bisphenols and phosgene, although the use of diphenyl carbonate as an alternative component is of increasing interest (see Example 4.4). Instead of free acids, cyclic carboxylic... 

Diesters.—Phase-transfer conditions, using aqueous carbonate as base, have been found for effecting Michael additions of malonic esters and acetoacetates to a,/3-unsaturated aldehydes yields vary between 44 and 65%. Monoalkylated material is obtained as the sole product (43% yield remainder starting material) from the reaction of dimethyl malonate with 1,5-dibromopentane when alumina pre-treated with NaOMe is used as base/ When more of the base is employed, only the intramolecular cyclization product is formed. A new approach to the mono-alkylation of malonates is use of the stable, non-hygroscopic sodium salt... 

Dimethyl sulfate, a diester of sulfuric acid, is a commercially available liquid used as a methylating agent. Nucleophiles readily attack the electrophilic methyl carbon atom by an reaction to give methylated products. The methyl sulfate ion is an excellent leaving group because it is resonance stabilized, and only weakly basic. 

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