Decarboxylation ketones from

Intramolecular photoinduced electron transfer in (58) leads to decarboxylation to give hydroxylactams in good yield (Griesbeck et al.), and irradiation of either the dextro or /eavo-rotatory crystals from the self-assembly of acridine and diphenyl acetic acid molecules, is reported to induce a decarboxylating condensation to give (+) or (—)-(59) with ees in the 35% region (Koshima et al,). The formation of ketones from the photolysis of nitrites is a low-yield process in... 

Kamimura et al. speculate that the extra oxygen needed for the oxidative decarboxylation came from the decomposition of 1-propanol to propane, while Claridge et al. proposed that any surface oxygen could be used. Kamimura et al. reported good results for synunetric ketone formation using other primary... 

The preparation of ketones in particular of asymetrically substituted ketones from aldehydes is desirable since the latter are readily available, for example via the oxo-synthesis. Isomerizations of this type, for example over catalysts of mixed oxides containing tin, molybdenum and copper, are known. The disadvantages here are that only low selectivities are achieved at satisfactory conversions, and the best results with regard to selectivity and catalyst life can be obtained only with the addition of steam. Therefor, in the industrial production of asymmetrically substituted ketones, it was necessary to use the condensation of different organic acids with decarboxylation. In this process, the inevitable production of symmetrically substituted ketones and of carbon dioxide is a disadvantage. ATdol condensation with subsequent hydrogenation is another possibility but requires very often two reaction stages. 

Sodium bromide Decarboxylative ring contraction Cyclopropyl ketones from -acyl-y-lactones... 

Ketones from / -ketocarboxylic acids s. 28, 733 stereoselective decarboxylation, in refluxing dioxane cf. Y. Kishi et al., Tetrah. Let. 1971, 4657... 

Decarboxylative elimination from sodium glycidates (59) using lead tetraacetate affords an efficient route to unsaturated ketones. A similar sequence via the epoxysulphoxide (60) has been reported. In these sequences it may be noted that the carbonyl is introduced as a masked nucleophilic acyl group (Scheme 50). 

The syntheses of a-alkylamino-acetals and the corresponding a-alkylamino-ketones from a-halogeno-ketimines, a-amino-ketones from benzilmonoamines, 3-arylamino-ketones from 3-carbamyloxy-ketones by decarboxylation, and chiral N- and iV,A( -substituted diamines and diamino-alcohols from amino-acids have also been reported. 

Ketones from y -ketocarboxylic acid esters with protection of the keto group as cyclic ketal Decarboxylation with cleavage of ketals... 

Geranyl acetoacetate (685) is converted into geranylacetone (686). On the other hand, a mixture of E- and Z-isomers of 688 is obtained from neryl acetoacetate (687). The decarboxylation and allylation of the allyl malonate or cyanoacetate 689 affords the o-allylated acetate or nitriie[447]. The trifluoromethyl ketone 691 is prepared from cinnamyl 4.4,4-trifluoroacetoace-tate (690)[448],... 

Ailyl enol carbonates derived from ketones and aldehydes undergo Pd-cat-alyzed decarboxylation-elimination, and are used for the preparation of a, /3-unsaturated ketones and aldehydes. The reaction is regiospecific. The regio-isomenc enol carbonates 724 and 726, prepared from 723, are converted into two isomeric enones, 725 and 727. selectively. The saturated aldehyde 728 can be converted into the a,/3-unsaturated aldehyde 730 via the enol carbonate 729[459]. 

In addition to formation from a ketone, the hydra2ones can be obtained from dicarbonyl compounds by a Japp-Klingemann reaction. This is especially useful for P-ketoesters and P-ketoacids, which undergo either deacylation or decarboxylation. 

Reactions. Heating an aqueous solution of malonic acid above 70°C results in its decomposition to acetic acid and carbon dioxide. Malonic acid is a useful tool for synthesizing a-unsaturated carboxyUc acids because of its abiUty to undergo decarboxylation and condensation with aldehydes or ketones at the methylene group. Cinnamic acids are formed from the reaction of malonic acid and benzaldehyde derivatives (1). If aUphatic aldehydes are used acryhc acids result (2). Similarly this facile decarboxylation combined with the condensation with an activated double bond yields a-substituted acetic acid derivatives. For example, 4-thiazohdine acetic acids (2) are readily prepared from 2,5-dihydro-l,3-thiazoles (3). A further feature of malonic acid is that it does not form an anhydride when heated with phosphorous pentoxide [1314-56-3] but rather carbon suboxide [504-64-3] [0=C=C=0], a toxic gas that reacts with water to reform malonic acid. 

Related and equally important reactions are the acetoacetic ester synthesis and the eyanoaeetie ester synthesis Here too the initial substituted product can be hydrolyzed and decarboxylated, to yield a ketone 11 (i.e. a substituted acetone) from acetoacetic ester 10, and a substituted acetonitrile 14 from eyanoaeetie ester 13 respectively. Furthermore a substituted acetoacetic ester can be cleaved into a substituted acetic ester 12 and acetate by treatment with strong alkali ... 

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)... 

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