1.3- dicarbonyl compounds 1,3-diketones

Several 1,4-dicarbonyl compounds are prepared based on this oxidation. Typically, the 1,4-diketone 10 or the 1,4-keto aldehyde 12 can be prepared by the allylation of a ketone[24] or aldehyde[61,62], followed by oxidation. The reaction is a good annulation method for cyclopentenones (11 and 13). Syntheses of pentalenene[78], laurenene[67], descarboxyquadrone[79], muscone (14 R = Me)[80]) and the coriolin intermediate 15[71] have been carried out by using allyl group as the masked methyl ketone (facing page). 

Aldol condensations of dicarbonyl compounds—even diketones—occur mtramo lecularly when five or six membered rings are possible... 

MONOPROTECTION OF DICARBONYL COMPOUNDS Selective Protection of a- and /3-Diketones... 

The initially formed ]5-dicarbonyl compounds are subject to further photo-transformations. One example is provided in the case of epoxy ketone (88), where the resulting /5-diketone (89) undergoes partly a-cleavage and acyl-alkyl... 

The major development in the Knorr pyrrole synthesis has been access to the amine component. For example, use of preformed diethyl aminomalonate with 1,3-diketones affords much higher yields of pyrroles 14. Reaction of 6-dicarbonyl compounds with hydroxylamine 0-sulfonic acid gives pyrroles 15 in one step. Weinreb a-aminoamides have found use in the Knorr pyrrole synthesis of a wide variety of pyrroles 16. °... 

A route to pyridines which involves an isolated 1,5-dicarbonyl compound, has been reported. Aldol reaction of enone 57 with methylketone 58 generated 1,5-diketone 59. When this was submitted to the reaction conditions for a Krohnke reaction, thiopyridine 60 was isolated. 

The coupling reaction of arenediazonium ions with semidione radicals (12.84, obtainable by reduction of 1,2-diketones, 12.83) is also included here in the discussion of 1,3-dicarbonyl compounds, although it is a coupling with a nucleophilic radical and does not strictly belong in this context. The reaction (Scheme 12-43) was... 

P 38] Ethanol solutions of ethyl propiolate and diisopropylethylamine were pumped via electroosmotic flow through the micro channels of the reactor [8], By mixing thereof the enolate was obtained. By subsequent contacting with the 1,3-dicarbonyl compound, the product was obtained. The temperature was set to room temperature. In a period of 20 min a volume sufficiently large for analysis was sampled. The reaction product spectra was analyzed by GC/MS via comparison with synthetic standards. The remaining amount of diketone was used for calculating conversions. 

Aside from alcohols, other oxygen nucleophiles have also participated in hydroalkoxylation reactions with alkynes. The most common of these are 1,3-dicarbonyl compounds, whose enol oxygens are readily available to add to alkynes. Cyclization reactions of this type have been carried out under Pd(0) catalysis with various aryl or vinyl iodides or triflates, often in the presence of CO, affording the corresponding furan derivatives (Equation (95)).337-340 A similar approach employing cyclic 1,3-diketones has also been reported to prepare THFs and dihydropyrans under Pd, Pt, or W catalysis.341 Simple l-alkyn-5-ones have also been isomerized to furans under the influence of Hg(OTf)2.342... 

Cyclopentenones. 1,3-Dicarbonyl compounds add to enol ethers or esters (terminal) in the presence of Mn30(OAc)7 (excess) to form l-alkoxy-l,2-dihydro-furans. These can be converted to a 1,4-diketone, which undergoes aldol cyclization to fused (or spiro) cyclopentenones.1... 

Utilization of fluoroalkyl-substituted dicarbonyl compounds is accompanied with side reactions. Trifluoro diketone 49 undergoes an acidic Claisen cleavage in ethanol with formation of dicyanoketone 50, which... 

Beside the Friedel-Crafts-type alkylation of arenes, the direct functionalization of 2,4-pentanediones is of great interest in Lewis acid catalysis. Although Pd-catalyzed Tsuji-Trost type allylations of 1,3-diketones are known, direct benzylation procedures catalyzed by Lewis acids are less explored [40-43]. Based on the previously described Friedel-Crafts alkylation of arenes and heteroarenes, the Rueping group developed a Bi(OTf)3-catalyzed benzylation of 2,4-pentanediones. Alcohols such as benzyl, allyl or cinnamyl alcohols were used as the electrophilic component to yield important 2-alkylated 1,3-dicarbonyl compounds. Initially, different Bi(III) salts were screened. In contrast... 

The use of other 1,3-dicarbonyl compounds as nucleophilic species was also investigated in this reaction. In particular, unsymmetrical diketones were tested in the condensation, giving rise to mixtures of C-glycosides [111, 114]. 

In the second study, diketones were used as electrophiles and reacted with N-benzoylglycine to give a (Z/E) mixture of oxazolones 366 and 367 derived from condensation at the less hindered carbonyl group of the 1,2-dicarbonyl compound (Scheme 7.116). The ( )-isomers 367 were used as starting materials to prepare (Z) -5 - alky lidene- 3 - (benzoy lamino) -2(5//)-furanones 368... 

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