Reagents Oxalic Acid Derivatives

Derivatives of oxalic acid should yield (fused) dihydropyrimidines substituted by a carboxylic acid derivative in the 2-position, but the reaction has been little explored. 2-Amino-3-ethoxalylaminomethylpyrazine (76) resisted 

Similar attempts to cyclize 4-amino-3-benzyl- or 4-amino-1-methy 1-5-ethoxalylaminomethyl-1,2,3-triazole (see 20) were unsuccessful. Surprisingly, 5-aminomethyl-3-benzyl- and 5-aminomethy 1-1 -methy 1-4-oxamoylamino-1,2,3-triazoles spontaneously isomerized to 4-amino-3-benzyl- and 4-amino-l-methyl-5-oxamoylaminomethyl-l,2,3-triazoles, which resisted ring closure with stannic chloride, phosphoryl chloride, or boiling butanolic sodium butoxide.69 

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Because of the structural requirements of the bielectrophile, fully aromatized heterocycles are usually not readily available by this procedure. The dithiocarbamate (159) reacted with oxalyl chloride to give the substituted thiazolidine-4,5-dione (160) (see Chapter 4.19), and the same reagent reacted with iV-alkylbenzamidine (161) at 100-140 °C to give the 1 -alkyl-2-phenylimidazole-4,5-dione (162) (see Chapter 4.08). Iminochlorides of oxalic acid also react with iV,iV-disubstituted thioureas in this case the 2-dialkylaminothiazolidine-2,4-dione bis-imides are obtained. Thiobenzamide generally forms linear adducts, but 2-thiazolines will form under suitable conditions (70TL3781). Phenyliminooxalic acid dichloride, prepared from oxalic acid, phosphorus pentachloride and aniline in benzene, likewise yielded thiazolidine derivatives on reaction with thioureas (71KGS471). 

Multiple products are possible from C02 hydrogenation, but all of the products are entropically disfavored compared to C02 and H2 (Scheme 17.1). As a result, the reactions must be driven by enthalpy, which explains why formic acid is usually prepared in the presence of a base or another reagent with which formic acid has an exothermic reaction. Of the many reduction products that are theoretically possible, including formic acid, formates, formamides, oxalic acid, methanol, CO, and methane, only formic acid and its derivatives are readily prepared by homogeneous catalysis. 

Reaction of oxalyl chloride with compound 301 gives the thiazolidine-4,5-dione 302 (Scheme 146), and the same reagent with A-alkylbenzamidine 303 at 100-140G affords the l-alkyl-2-phenylimidazole-4,5-dione 304 (Scheme 147). Imi-nochlorides of oxalic acid react with N,N-disubstituted thioureas to give the 2-dialkylaminothiazolidine-4,5-dione bis-imides 305. Phenyliminooxalic acid dichloride likewise yielded thiazolidine derivatives on reaction with thioureas <1971KGS471>. 

The same strategy has been used to prepare trans bicyclic enones. The protected C5 phosphonylated aldehyde is obtained in 84% yield by a CuBr SMe2-mediated Michael addition of the Grignard reagent derived from 4-chlorobutyraldehyde diethyl acetal to a 5-phosphonylated 2,3-dihydro-4-pyridone in THF. Subsequent room-temperature hydrolysis of the acetal using aqueous oxalic acid in THF affords a near-quantitative yield of the crude aldehyde, which undergoes an intramolecular Homer-Wadsworth-Emmons reaction under treatment with Et3N/LiCl in THF at room temperature (89%). ... 

Keto aldehydes. The Grignard reagent of this acetal reacts with acid chlorides in refluxing THF to form an intermediate that is hydrolyzed by aqueous oxalic acid to a y-keto aldehyde (example I). The Grignard derivative of 2-... 

The reaction of the monoepoxides with phenol was followed at 120 °C in melt by determining the epoxy groups content. Equimolar ratios of the reagents were used. Oxalic acid, Ar,AT-dimethylbenzylamine and ZnCl2 (1% of the monoepoxide) were applied as catalysts. It was found that the reaction rates of the glycidyl and the epoxycyclohexane derivatives differ substantially (Fig. 8). 

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