Oxalic ester synthesis

These are reactions involving CO, a substrate, and an oxidizing agent. Probably the most important reaction is that used for oxalate ester synthesis the ester can be used as a precursor for ethylene glycol. 

In the model reaction of the oxalate ester synthesis [10c], the efficiency and selectivity (oxalate vs. carbonate) of carbonylation of methanol with a stoichiometric amount of Pd(OAc)2 were examined as a function of added phosphine, base, and CO pressure. Without added phosphine, Pd(OAc)2 is very effective in forming dimethyl oxalate at room temperature. Use of PPhs slowed the formation of the oxalate, a reaction temperature of ca. 50°C being required. At room temperature Pd(COOMe)(OAc)(PPh3)2 was isolated. More basic phosphine, e.g. PBu3 almost completely inhibited the oxalate formation. The formation of oxalate decreased and that of dimethyl carbonate increased by the use of low CO pressure and some bases (e.g. EtsN). A reaction scheme accounting for these observations was presented (Scheme 8.7). 

Eschweiler s. Clarke Ester condensation (s. a. Dieck-mann cyclization, Oxalic ester synthesis)... 

Oxalic ester synthesis—Enolesters from ketones. 6 g. dl-zl5,14-3.Ethylenedioxy-lly ,18-oxido-16-oxo-18-tetrahydropyranyloxyandrostadiene and dimethyl oxalate in benzene added dropwise to NaH in oil (Metal Hydrides, Inc., Beverly, Mass., USA) and benzene, stirred 48 hrs. at 30° in a slow Ng-stream, the crude product dissolved in benzene, and allowed to stand at room temp, overnight with acetic anhydride and pyridine 6.61 g. methyl dl-J5,14,17(20)-3-ethylene-dioxy-1 ly, 18- oxid o-16- oxo-18- tetrahydropyranyloxy - 20 - acetoxypregnatrien-21-ate, 6 g. suspended in an ice-cold 10 1 mixture of morpholine and water, stirred 3-4 hrs. until a clear soln. results, allowed to stand 24 hrs. at ca. 10°, evaporated almost to dryness at 35-40°/0.05 mm., a mixture of benzene and ether then pyridine added, ice-cooled, acetic anhydride added, and allowed to stand 24 hrs. at room temp. 5.55 g. dl-j5,14,17(20)-3-ethylenedioxy-ll, 18-oxido-16-oxo-18-tetrahydropyranyloxy-20-acetoxypregnatrien-21-ic acid morpholide.—Morpholine is preferred to other sec. amines because of its good solvent properties (cf. Synth. Meth. lA, 87). Use of anhydrous amines caused decomposition. K. Heus-ler, P. Wieland, and A. Wettstein, Helv. A2, 1586 (1959). 

Carboxylic from a-ketocarboxylie acids Carboxylation by oxalic ester synthesis... 

Oxalic ester synthesis s. 11, 813 Sodium hydride Alkylation of ketones... 

Oxalic ester synthesis 16, 812 Oxalyl chloride, reaction with amines 16, 502 Oxamic acid derivatives... 

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