Dicarbonyl compounds Keto amides

Keto amides (see Dicarbonyl compounds) Keto esters (see Dicarbonyl compounds) Ketones (see also Dicarbonyl compounds, Unsaturated carbonyl compounds) From alcohols by oxidation... 

Diazocarbonyl compounds can be prepared on insoluble supports by diazo group transfer with sulfonyl azides or by diazotization of primary amines. Diazo group transfer from sulfonyl azides to 1,3-dicarbonyl compounds proceeds on cross-linked polystyrene as smoothly as in solution (Table 10.19). When 3-keto esters or amides are... 

The conjugate addition of carbonyl anions catalysed by thiazolium salts (via umpol-ung) that is fully operative under neutral aqueous conditions has been accomplished. The combination of a-keto carboxylates (157) and thiazolium-derived zwitterions (e.g. 160) in a buffered protic environment (pH 7.2) generates reactive carbonyl anions that readily undergo conjugate additions to substituted o /3-unsaturated 2-acylimidazoles (158) to produce (159). The scope of the reaction has been examined and found to accommodate various a-keto carboxylates and /3-aryl-substituted unsaturated 2-acylimidazoles. The optimum precatalyst for this process is the commercially available thiazolium salt (160), a simple analogue of thiamine diphosphate. In this process, no benzoin products from carbonyl anion dimerization were observed. The resulting 1,4-dicarbonyl compounds (159) can be efficiently converted into esters and amides by way of activation of the A-methylimidazole ring via alkylation.181... 

The reductive coupling of carbonyl compounds with formation of C-C double bonds was developed in the early seventies and is now known as McMurry reaction [38, 39]. The active metal in these reactions is titanium in a low-valent oxidation state. The reactive Ti species is usually generated from Ti(IV) or Ti(III) substrates by reduction with Zn, a Zn-Cu couple, or lithium aluminum hydride. A broad variety of dicarbonyl compounds can be cyclized by means of this reaction, unfunctionalized cycloalkenes can be synthesized from diketones, enolethers from ketone-ester substrates, enamines from ketone-amide substrates [40-42], Cycloalkanones can be synthesized from external keto esters (X = OR ) by subsequent hydrolysis of the primary formed enol ethers (Scheme 9). 

Like other, 8-dicarbonyl compounds, the substituted keto amides (X)—(XV) are very reactive and represent the key intermediates in a complex set of side reactions [95]. A considerable amount of research has been devoted to the elucidation of the reactions of these compounds under polymerization conditions [118—120,124,125,127,128, 130,131, 134—143]. With respect to the high reactivity of carbonyl groups and the adjacent —CH2— or i CH- groups, the structures like (X)—(XV) are unstable at elevated temperatures and even less stable in the presence of a strong base. Bukac and Sebenda [137] showed that keto amides with one hydrogen atom at the nitrogen decompose very easily in the presence of base into isocyanate which takes part in many subsequent reactions, scheme (45). The most important consequence of side reactions is the fact that water is present even if the anionic polymerization is started under... 

The spectrum of applications of potassium permanganate is very broad. This reagent is used for dehydrogenative coupling [570], hydrox-ylates tertiary carbons to form hydroxy compounds [550,831], hydroxylates double bonds to form vicinal diols [707, 296, 555, 577], oxidizes alkenes to a-diketones [560, 567], cleaves double bonds to form carbonyl compounds [840, 842, 552] or carboxylic acids [765, 841, 843, 845, 852, 869, 872, 873, 874], and converts acetylenes into dicarbonyl compounds [848, 856, 864] or carboxylic acids [843, 864], Aromatic rings are degraded to carboxylic acids [575, 576], and side chains in aromatic compounds are oxidized to ketones [566, 577] or carboxylic acids [503, 878, 879, 880, 881, 882, 555]. Primary alcohols [884] and aldehydes [749, 868, 555] are converted into carboxylic acids, secondary alcohols into ketones [749, 839, 844, 863, 865, 886, 887], ketones into keto acids [555, 559, 590] or acids [559, 597], ethers into esters [555], and amines into amides [854, 555] or imines [557], Aromatic amines are oxidized to nitro compounds [755, 559, 592], aliphatic nitro compounds to ketones [562, 567], sulfides to sulfones [846], selenides to selenones [525], and iodo compounds to iodoso compounds [595]. 

Reaction of sugar lactone with ester enolate (the Claisen condensation) gives -keto ester, the resulting 1,3-dicarbonyl compound immediately reacts with the hydroxyl group present in the same molecule to afford a lactol with an axial hydroxyl group. In a recent example shown in O Scheme 4 [8], the product of the reaction was further transformed to the corresponding nitrile or amide by addition of cyanide or a Ritter reaction with benzonitrile in the presence of TMSOTf as a Lewis acid. 

Intramolecular addition of allylsilanes performed under chelation-controlled conditions represents an efficient method in which useful levels of stereoselectivity can be achieved. This process has been demonstrated for a variety of a-alkoxy, a,3-dialkoxy and p-dicarbonyl compounds, including 3-keto esters, P-keto amides and P-keto lactones. 

Thiazoles can also be derived from 1,4-dicarbonyl compounds, which are available through N-H insertion reactions of rhodium carbenoids <04T3967>. For example, the dirhodium(II) carboxylate-catalyzed reaction of diazocarbonyl compound 7 in the presence of primary amide 8 results in the formation of a-acylaminoketone 9, which is converted into thiazole 10 by treatment with Lawesson s reagent. The cyclodehydration of P-keto thioamide 11 to thiazole 12 is carried out with pyridine-buffered phosphorus oxychloride <04JA12897>. 

The asymmetric a-hydroxylation of p-keto esters and p-keto amides is a useful strategy for the synthesis of a-hydroxy p-dicarbonyl compounds. Using TBHP 102 as the oxidant, the tV,A7 -dioxide magnesium catalyst was efficient for the enantioselective a-hydrojylation of p-keto esters 101 and p-keto amides, leading to a-hydro grdicarbonyl compounds 103 in high yields and with excellent enantioselectivities. Importantly, this reaction could be scaled up to gram scale (Scheme 3.31). ... 

The synthesis of tetra-substituted ureas (1997JOC4155), amides (2000JOC8210), p-dicarbonyl compounds (2000JOC3679), and p-keto esters (2004JOC6617) are all examples of acylation by benzotriazolides and the subject of acylation at C-, N-, 0-, and S- centers has been thoroughly reviewed (2005SL1656). A few special examples follow, however, to illustrate the versatility of Bt methodology. 

The synthesis of A/-acyl-a-chloroglycine and its use in the preparation of other a-substituted glycines has been described.N-Acylhemiaminals, prepared from glyoxylic acid and amides, carbamates, or ureas, can be converted into N-acyl-a-arylglycines by reaction with aromatic hydrocarbons in sulphuric acid. The same type of hemiaminals may be converted into N-acyl-y-keto-a-amino-acids by reactions with 1,3-dicarbonyl compounds again in the presence of concentrated sulphuric acid. °°... 

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