Diketones conversion

This rapid formation of the crystalline quinoxaline derivative can therefore be used to identify 1,2-diketones conversely, a nuclear-substituted o-phenyl-enediamine can be identified by the quinoxaline derivative which it forms with a known 1,2-diketone such as benzil. 

A mixture of an acid anhydride and a ketone is saturated with boron trifluoride this is followed by treatment with aqueous sodium acetate. The quantity of boron trifluoride absorbed usually amounts to 100 mol per cent, (based on total mola of ketone and anhydride). Catalytic amounts of the reagent do not give satisfactory results. This is in line with the observation that the p diketone is produced in the reaction mixture as the boron difluoride complex, some of which have been isolated. A reasonable mechanism of the reaction postulates the conversion of the anhydride into a carbonium ion, such as (I) the ketone into an enol type of complex, such as (II) followed by condensation of (I) and (II) to yield the boron difluoride complex of the p diketone (III) ... 

The conversion of 4,5-dicyanothiazoles to diketones has been attempted (91). A difference in reactivity between the two cyano groups has been observed the least labile is the group in the 5-position. These Grignard reactions are limited and lead to 4-acetyl-5-cyanothiazole (Scheme 25). 

Diketones and tetraketones derived from aromatic compounds by conversion of two or four SCH groups into keto groups, with any necessary rearrangement of double bonds to a quinonoid structure, are named by adding the suffix -quinone and any necessary affixes. 

Noncatalytic oxidation of propylene to propylene oxide is also possible. Use of a small amount of aldehyde in the gas-phase oxidation of propylene at 200—350°C and up to 6900 kPa (1000 psi) results in about 44% selectivity to propylene oxide. About 10% conversion of propylene results (214—215). Photochemical oxidation of propylene with oxygen to propylene oxide has been demonstrated in the presence of a-diketone sensitizers and an aprotic solvent (216). 

The first in this series to be reported was 4-oxoisoxazoline-3,5-dicarboxylic acid diethyl ester, which was formed by the reaction of nitrous acid on diethyl acetonedicarboxylate in 1891. Quilico described a number of syntheses in his 1962 review and the most general include the reaction of hydroxylamine and a-hydroxy-(or acetoxy)- 3-diketones and the conversion of 4-isoxazolediazonium salts to the hydroxy moiety (62HC(17)1, p. 3). Additional syntheses reported were the oxygenation of a 4-boric acid derivative (67JOM(9)l9) and peroxide oxidation of a 4-nitro-2-isoxazoline (Scheme 151) (79ZOR2436). 

Methylation at the 9a-position of the A3,11-diketone (23) to yield (24) has been achieved by reaction of (23) with sodium bistrimethylsilylamide and methyl iodide. The base is soluble in most organic solvents and this facilitates rapid and almost quantitative conversion of a ketone into its enolate. 

When the enone chromophore of the diketone (148) is excited selectively using 2537 A-light, a smooth conversion to the two stereoisomeric cyclopropyl diketones (149) and (150) takes place exclusively. Experiments... 

Kurath described the conversion of 3a,17y5-diacetoxy-5)9-androstan-12-one (partial structure 78) to diketone (79) by bromination of (78) and hydrolysis of the C-11 epimeric bromo ketones... 

Jones and Civcir prepared a variety of alternating oligomeric furanipyridine compounds and studied their NMR chemical shifts as well as the pKa values for the corresponding conjugate acids. All of these compounds were synthesized by Paal-Knorr reactions of 1,4-diketones with hot polyphosphoric acid. A representative example is the conversion of 24 into 25 in 82% yield. ... 

Until 1952, it was postulated that the Paal thiophene synthesis proceeded via an initially formed furan via dehydration of the 1,4-diketone, followed by conversion of the furan to... 

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)... 

The reaction of the aldehyde 174, prepared from D-glucose diethyl dithio-acetal by way of compounds 172 and 173, with lithium dimethyl methyl-phosphonate gave the adduct 175. Conversion of 175 into compound 176, followed by oxidation with dimethyl sulfoxide-oxalyl chloride, provided diketone 177. Cyclization of 177 with ethyldiisopropylamine gave the enone 178, which furnished compounds 179 and 180 on sodium borohydride reduction. 0-Desilylation, catalytic hydrogenation, 0-debenzyIation, and acetylation converted 179 into the pentaacetate 93 and 5a-carba-a-L-ido-pyranose pentaacetate (181). 

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. 

OS 57] [R 6] [P 40] One of the first examples of parallel multi-reaction was performed in a Caliper chip [18], By 2 x 2 combinations of two aldehydes and two 1,3-diketones, four cycloadducts were generated simultaneously in one run on one chip (Figure 4.71). The conversions were comparable to those for the single runs, with one exception. Also, cross-contamination was observed. It ranged from a few percents to about 50%. It should be pointed out that despite these initial drawbacks the demonstration of multi-reaction feasibility is a further valuable step in micro channel processing. 

Literature search showed the dihydro-chromandione motif in 53, or other related system, is relatively unknown and/or under-investigated, and the proposed conjugate reduction to this system was unprecedented. Fortuitously, our attempt employed NaBH4 in MeOH at 0 °C, and while a new spot was rapidly produced, the conversion was slow. When the solution was warmed to ambient temperature and additional aliquots of NaBH4 were added, a mixture of diketone 55 and hydroxy ketone 56 was isolated. In subsequent trials, 55 could be reduced cleanly to 56 especially at elevated temperatures. 

Epoxides are believed to be intermediates in the conversion of the enol ethers of 1,3-diketones (ketoaldehydes are less satisfactory) into 2,4-substituted furans by means of the trimethylsulfonium ylids. No epoxides could be isolated, however, nor was it necessary to use acid to effect cy-clization. Methoxydimethylsulfonium ylids were less efficient and tended to produce thiabenzene oxides instead, so Scheme 8 remains speculative.57 The use of thioenols instead of 1,3-diones is advantageous.233... 

It is possible to form cyclic ethers from diketones as seen by the cyclic hemike-tal formed by the reduction of 1,5-cyclooctanedione (Eq. 228) and the conversion of 2,5-hexanedione into cis- and /ran.v-2,5 -di me(In Itetrahydrofuran (Eq. 229).392 A naphthopyran can be formed in a similar manner.339... 

Alternatively, Ballini devised a new strategy to synthesize tri-alkylated pyrroles from 2,5-dialkylfurans and nitroalkanes <00SL391>. This method involves initial oxidation of 2,5-dimethylfuran with magnesium monoperoxyphthalate to cA-3-hexen-2,5-dione (6). Conjugate addition of the nitronate anion derived from the nitro compound 7 to 6 followed by chemoselective hydrogenation of the C-C double bond of the resulting enones 8 (obtained by elimination of nitrous acid from the Michael adduct) completes the conversion to the alkylated y-diketones 9. Final cyclization to pyrroles 10 featured improved Paal-Knorr reaction conditions involving reaction of the diketones with primary amines in a bed of basic alumina in the absence of solvent. 

Acylbenzotriazoles 162 are efficient C-acylation reagents for the regioselective conversion of ketone enolates into P-diketones . Diethyl(l-benzotriazolmethyl)phosphinate (163) was found to be a convenient reagent for the stereoselective preparation of (E)-l-(l-alkenyl)benzotriazoles <00SC1413>. The novel three-carbon synthon 1-(1//-133-... 

---