Oxalic acid chloride esters

A variant of this route to 2-unsubstituted chromones employs oxalic acid half-ester half-acid chloride, which gives a 2-ethoxycarbonyl-chromone, hydrolysis and decarboxylation of which achieves the required result. Diethyl carbonate as the ester gives rise to 2,4-dioxygenated heterocycles, which exist as 4-hydroxy-coumarins. The condensation of a salicylate with an ester, using three mole equivalents of base also leads through to 4-hydroxy-coumarins, as illustrated below. ... 

C0 H 1 COgH Oxalic acid (also esters and acid chloride) CHO 1 CHO Glyoxal (as aqueous solution) cii. —CO Diacetyl CH —CO... 

Ethyl (cMoroformyl)formate (oxalic acid monoethyl ester chloride), b.p. 130-132° (cf. page 247), can be obtained by way of ethyl dichlorodiethoxyacetate which splits off ethyl chloride, sometimes spontaneously and always in the presence of a little metallic plat-... 

Figure 4 L-(+)-ascorbic acid 244, L-(+)-tartaric acid ethyl ester 245, and (S)-phenylethyl amide of oxalic acid chloride 246.

Oxidative Garbonylation. Carbon monoxide is rapidly oxidized to carbon dioxide however, under proper conditions, carbon monoxide and oxygen react with organic molecules to form carboxyUc acids or esters. With olefins, unsaturated carboxyUc acids are produced, whereas alcohols yield esters of carbonic or oxalic acid. The formation of acryUc and methacrylic acid is carried out in the Hquid phase at 10 MPa (100 atm) and 110°C using palladium chloride or rhenium chloride catalysts (eq. 19) (64,65). 

Acid moieties include formic acid itself, formates and orthoesters, formamide, DMF dimethyl acetal and ethyl diethoxyacetate, acids, acid chlorides and anhydrides, the last including a rare [3,4-oxalate esters, 2-acyl or 2-ethoxycar-bonyl derivatives e.g. 180) are formed. 

A thioamide of isonicotinic acid has also shown tuberculostatic activity in the clinic. The additional substitution on the pyridine ring precludes its preparation from simple starting materials. Reaction of ethyl methyl ketone with ethyl oxalate leads to the ester-diketone, 12 (shown as its enol). Condensation of this with cyanoacetamide gives the substituted pyridone, 13, which contains both the ethyl and carboxyl groups in the desired position. The nitrile group is then excised by means of decarboxylative hydrolysis. Treatment of the pyridone (14) with phosphorus oxychloride converts that compound (after exposure to ethanol to take the acid chloride to the ester) to the chloro-pyridine, 15. The halogen is then removed by catalytic reduction (16). The ester at the 4 position is converted to the desired functionality by successive conversion to the amide (17), dehydration to the nitrile (18), and finally addition of hydrogen sulfide. There is thus obtained ethionamide (19)... 

One of the few nonnitrogenous compounds to show spasmolytic activity is a rather simple chromone. Acylation of the phenolic ketone, 31, with the half ester-half acid chloride from oxalic... 

The treatment of kasuganobiosamine with dimethyl ester of oxalic acid followed by concentrated aqueous ammonia gave two kinds of amides. The amide (11a) with pK a 7.6 was identical with the amide of kasugamycinic acid, which was prepared from kasugamycinic acid by treatment with anhydrous hydrogen chloride-methanol followed by concentrated aqueous ammonia. The other isomer (lib) with pK a 7.8, was named amide of isokasugamycinic acid. 

In addition to the acid anhydride12,14,17-19 shown as the source of the carbon at C-5 in the final product [Eq. (1)], ketene,20 reactive acids such as formic21 and acrylic,22 acid chlorides,10,23-26 esters,27 ortho esters,28-34 ethyl oxalate,35 amides,35 and iminoethers36 [Eqs. (12-14)] may also furnish the C-5 carbon. 

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