Ketenes 3-Keto acids

Ketene diethylacetal, 23, 43 Ketene, diethyl ketal, 23, 43 Ketene dimer, 21, 4, 64 Ketene lamp, 21, 65 Keto acid, 20, 2... 

Ketals, of hexitols, IV, 223 Ketene, acetylation of starch with, I, 290 Keto acids, a- and 0-, specificity of carboxylase action on, V, 50 a-Keto acids, aromatic, V, 50 0-Keto acids, oxidation of, II, 148 a-Ketobutyric acid, V, 50 a-Ketocaproio acids, V, 50 Ketogenesis, in liver slices, II, 155 Ketolysis, II, 120, 146, 147, 158 in liver slices, II, 155 Ketolytic, II, 146... 

On heating with actueou- - HCl, tlte alkylated (or dialkylatedl acetoacetic eater is hydrolyzed to a /ft keto acid and then decarboxytated to yield the ketene product. The decarboKylation occurs in the same way as in the maU onic ester synthesis and involves a ketone enol as initial product. 

The photolysis of the 6-oxo-3a,5a-cyclo-19-oic acid (520) gives initially the 4-en-6-one (521), but in t-butanol a rapid photo-addition then affords the 4a-t-butoxy-6-hydroxy-lactone (522). Similar reactions transformed the methyl ester (523) into the ketonic derivative (525). Photolysis of the saturated keto-acid (526), in an alcohol as solvent, gave first the corresponding 6-monoester (527) of the 5,6-seco-6,19-dioic acid, and finally the 6,19-anhydride (528). Formation of the 6-ester (527) probably involves addition of the solvent alcohol to a keten intermediate. ... 

Ketazines, 395 Ketene, 76,275 Ketene thioaoetals, 284,413 Ketimines, 345 d-Keto acids, 538 a-Ketocarbenes, 100 7-Ketocholesteryl acetate, 51 5-Keto-6-cyano-5,6-secosteroids, 277... 

Ried and Mengler " found that ketene reacts with diazoketones at room temperature (toluene solution, 2 days) to form /8,y-butenolides (I) which are hydrolyzed to y-keto acids (2) reducible in turn to the corresponding acids (3). The sequence... 

When Ri of the enone is a sterically demanding fert-butyl group, tert-butyldimethylsilyl ketene acetals provide the syn keto acids (after saponification) as essentially one diastereomer (entries 1-3 and 6, Table 17). With other... 

Kerosene, purified, 24, 7 Ketene, 21, 13, 64 Ketene diethylacetal, 23, 45 Ketene, diethyl ketal, 23, 45 Ketene dimer, 21, 4, 64 Ketene lamp, 21, 65 Keto acid, 20, 2 -Ketoglutaric acid, 26, 42 Ketone, 2-Fluorenyl methyl, 28,3,63 Ketone, methyl 9-phenanthryl, 28,6 Ketone, methyl 2-thienyl, 28,1 Knoevenagel condensation, 23, 60 24, 92 25, 42, 51 27, 24 28, 24 Kolbc synthesis of an alkyl a,a>-dicar-boxylatc, 21, 48... 

Ainsworth has described in detail the syntheses and pyrolyses of keten alkyltrimethylsilyl and keten bis(trimethylsilyl) acetals, the latter providing a good route to / -keto-acids (Scheme 23). 

Full details have been published on the oxidative rearrangement of pyruvates to malonates. Whereas the reduction of dimethyl bismethylmalonate with sodium in xylene is reported to yield the keten acetal (9) in the presence of trimethylchlorosilane, when the solvent is ammonia a mixture of products is formed, including the cyclopropanediol di(trimethylsilyl)ether (10). This diol, on treatment with sodium methoxide, gives the products shown in Scheme 39, possibly by Cannizzaro disproportionation of the aldehyde (11). The mechanism of decarboxylation of monoethyl oxaloacetate has been studied as part of a general investigation of ) -keto-acid decarboxylation. 

In many preparations nearly quantitative yiefds are obtained by allowing the reactions to run at room temperature for about twenty-rfour hours. This is one of the simplest methods of bringing about the formation of a new carbon-carbon bond, and it affords a very attractive route to derivatives of /3-keto acids for example, esters of the tjq)e RCH2COCHRCO2C2H8 are obtained from the acids (RCH2CO2H) by converting the acid chlorides to the ketene dimers and allowing these to react with ethanol. 

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