A-Keto amides

Pd-catalyzed carbonylation of heteroaryl halides provides a quick entry to heteroaryl carbonyl compounds such as heteroaryl aldehydes, carboxylic acids, ketones, esters, amides, a-keto esters and a-keto amides. In addition, Pd-catalyzed alkoxycarbonylation and aminocarbonylation are compatible with many functional groups, and therefore, are more advantageous than conventional methods for preparing esters and amides [78],... 

Aromatic 1,2-diamines (46) condense readily with 1,2-diketones, a-keto amides, a-keto acids, or oxalic acid and provide quantitative yields in the solid state. For example, benzils (338) react with o-phenylenediamines (46) at room temperature upon milling and drying (Scheme 54). All products 339 are also obtained with 100% yield by heating to the temperatures given after initial stoichiometric cogrinding. Similarly 340 and 46a (70 °C, 15 min) give quantitatively compound 341 [104]. 

Oxidative rearrangement of x-keto esters and amides. a-Keto esters and amides undergo oxidative rearrangement when treated with sodium periodiate at pH 7-9 to... 

The o-keto ester 513 is formed from a bulky secondary alcohol using tricy-clohexylphosphine or triarylphosphine, but the selectivity is low[367-369]. Alkenyl bromides are less reactive than aryl halides for double carbonyla-tion[367], a-Keto amides are obtained from aryl and alkenyl bromides, but a-keto esters are not obtained by their carbonylation in alcohol[370]. A mechanism for the double carbonylation was proposed[371,372],... 

Particularly alkyl halides which have a perfluoroalkyl group at the /3-position undergo smooth carbonylation. Probably the coordination of fluorine to form a five-membered chelate ring accelerates the reaction. Double carbonylation to give the a-keto amide 915 is possible in Et NH with the fluorine-bearing alkyl iodide 914[769,770]. The ester 917 is obtained by the carbonylation of the /3-perfluoroalkyl iodide 916 in ethanol. 

Using a Keto Amide, Nitrile, Acyl Halide, or Related Synthon... 

Acid derivatives that can be converted to amides include thiol acids (RCOSH), thiol esters (RCOSR), ° acyloxyboranes [RCOB(OR )2]. silicic esters [(RCOO)4Si], 1,1,1-trihalo ketones (RCOCXa), a-keto nitriles, acyl azides, and non-enolizable ketones (see the Haller-Bauer reaction 12-31). A polymer-bound acyl derivative was converted to an amide using tributylvinyl tin, trifluoroacetic acid, AsPh3, and a palladium catalyst. The source of amine in this reaction was the polymer itself, which was an amide resin. 

The first substrate analogue inhibitors of FAAH were reported in 1994. The anandamide analogues prepared represented three elasses of putative transition-state inhibitors a-trifluoromethyl ketones, a-ketoesters and a-ketoamides [62], In the initial sereening studies, it was found that the trifluoromethyl ketone eompounds tested were effeetive inhibitors of AEA hydrolysis. A selected set of a-keto esters also inhibited hydrolysis, while a-keto amides were ineffective. In particular, arachidonyl trifluoromethyl ketone (32), gave almost 100% inhibition of anandamide hydrolysis. A detailed investigation of the structural requirements for FAAH inhibition with a-trifluoromethyl ketones has been carried out by Roger and co-workers [63]. 

A-Unsubstituted isoxazolidines such as 65 undergo facile decarboxylative peptide couplings with a-keto acids <06JA1452>. The use of water as solvent or cosolvent was particularly beneficial for the formation of amides in high yields. The methyl a-keto esters obtained could be saponified to the corresponding a-keto acids, and the (i-peptide chain could then be extended by reaction with another isoxazolidine. 

Table 10 Asymmetric hydrogenation of some a-keto esters or amides...

Recently, Borner and coworkers described an efficient Rh-deguphos catalyst for the reductive amination of a-keto acids with benzyl amine. E.e.-values up to 98% were obtained for the reaction of phenyl pyruvic acid and PhCH2COCOOH (entry 4.9), albeit with often incomplete conversion and low TOFs. Similar results were also obtained for several other a-keto acids, and also with ligands such as norphos and chiraphos. An interesting variant for the preparation of a-amino acid derivatives is the one-pot preparation of aromatic a-(N-cyclohexyla-mino) amides from the corresponding aryl iodide, cyclohexylamine under a H2/ CO atmosphere catalyzed by Pd-duphos or Pd-Trost ligands [50]. Yields and ee-values were in the order of 30-50% and 90 >99%, respectively, and a catalyst loading of around 4% was necessary. 

A different reaction involving the decarbonylation of an a-keto amide (129) is the basic idea of Monteiro s synthesis of cucurbitine (Scheme 30) (174). 

Ser proteases PI pocket binder Benzamide, a-keto amide 19, 141... 

Amides of keto acids were reduced to amides of hydroxy acids biochemically using Saccharomyces cerevisiae to give optically pure products [7059]. Refluxing with lithium aluminum hydride in ether for 6 hours reduced both the ketonic and the amidic carbonyl in A -methyl-5-phenyl-5-oxopentanamide and gave 82% yield of 5-methylamino-l-phenylpentanol [1134]. 

As with alkenes we consider first those oxidations which do not cleave the acetylenic bond giving a-diketones, or oxidation of alkynyl amines and ethers to a-keto amides and esters, and then consider oxidative alkyne cleavage to acids. 

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