Dimethyl oxalate, hydrolysis

The above example serves to iUustrate the basis of the procedure employed for the characterisation of aUphatic esters, viz., hydrolysis to, and identification of, the parent acids and alcohols. Most esters are liquids a notable exception is dimethyl oxalate, m.p. 54°. Many have pleasant, often fruit-hke, odours. Many dry esters react with sodium, but less readily than do alcohols hydrogen is evolved particularly on warming, and a sohd sodio derivative may separate on coohng (e.j/., ethyl acetate yields ethyl sodioacetoacetate ethyl adipate gives ethyl sodio cj/cZopentanone carboxylate). 

Diethyl oxalate is usually preferred because of its slower rate of hydrolysis. Satisfactory results are obtained in the precipitation of calcium, magnesium, and zinc thorium is precipitated using dimethyl oxalate. 

The reaction of n-butyllithium with 1-methylindazole gave the 1-lithiomethyl derivative, which formed the bisindazolyl compound by the action of carbon dioxide, followed by hydrolysis with acid.161 The 2,2 -thenils (79 X = S, R = 5-F, or 5-adamantyl) were made by the reaction of two molecules of the corresponding 2-lithiothiophene with dimethyl oxalate.103... 

Displayed below is the reaction route for the Reissert indole synthesis from c>-nitrotoluene and dimethyl oxalate, where the hydrolysis of methyl indole-2-carboxylate could be omitted, depending on the reaction conditions. 

Other PFHS methods that have been used for the production of crystalline precipitates by the controlled generation of the required anions in an appropriate aqueous solution include the hydrolysis of allyl chloride (Cl ), dimethyl oxalate ( 204 ), triethylphosphate (PO4 ), dimethylsulphate (SO4 ) and thioacetamide (S ). 

Following a suggestion by Penneman, Hermann demonstrated that a substantial separation of americium from lanthanum could be obtained by fractional precipitation of americium and lanthanum oxalates. The precipitation is effected in homogeneous solution the precipitant is generated by the slow hydrolysis of dimethyl oxalate. The oxalate precipitate is greatly enriched in americium (50% of the lanthanum can be rejected at each stage, with about 4% of the americium) [35]. 

In a situation where severe steric hindrance e.g., 16,16-dimethyl-20-keto-pregnanes) prevents enol acetate formation, an alternate scheme has been devised. Condensation of ethyl oxalate at C-21 produces, after hydrolysis, the 21-glyoxylic acid this on treatment with acetic anhydride and a strong acid catalyst such as perchloric acid gives both lactone acetates. 

Treatment of D-glucoascorbic acid (XV) with diazomethane gives a 2,3-dimethyl derivative (LXXIX) and this upon repeated treatment with silver oxide and methyl iodide yields 2,3,5,6,7-pentamethyl-D-glucoascorbic acid (LXXX). Ozonization of the latter followed by hydrolysis gives oxalic acid and 3,4,5-trimethyI-D-arabonic acid (LXXXI). This acid was shown to possess a free hydroxyl group at C2 by reason of the fact that the amide of LXXXI gives a positive Weerman reaction for a-hydroxy amides, i.e., when the amide is treated with sodium hypochlorite, sodium isocyanate is produced, the latter being identified by... 

During a synthesis of the Chlorothricolide, Roush and Sciotti encountered unexpected problems with the hydrolysis of the dimethyl acetal 54.1 [Scheme 2.54].112 Use of some of the standard hydrolysis conditions (oxalic acid, PPTS, PTSA, HO Ac, or trifluoroacetic acid — all in acetone) resulted in recovery of 54.1 or decomposition. Success was achieved by exploiting the mild Lewis acidic properties of the lithium cation under conditions first reported by Lipshutz and Harvey.113 Thus treatment of the dimethyl acetal 54,1 with lithium tetrafluoroborate in acetonitrile containing 2% water returned the desired aldehyde 54J in 97% yield after 2 h at room temperature. The reaction was also applied to the deprotection of a cyclic ketal in a synthesis of Pumi-liotoxin.114 115... 

For example, hydrolysis of esters of dicarboxylic acids belongs to such reactions. Thus, dimethyl ester of the oxalic acid is hydrolyzed through two steps... 

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