Ketones reagents

An enol is usually characterised by treatment with ketonic reagents or with phenylhydrazme (compare Section IV,114 and Table IV,114A), or by hydrolysis with acid, followed by the identification of the ketone. 

Intermediates benzene to ethyl phenyl ketone to ethyl m nitrophenyl ketone to m aminophenyl ethyl ketone to ethyl m fluorophenyl ketone Reagents propanoyl chloride AICI3 HNO3 H2SO4 Fe HCl then HO NaN02 H2O HCl then HBF4 then heat... 

Isatin (190) is a compound with interesting chemistry. It can be iV-acetylated with acetic anhydride, iV-methylated via its sodium or potassium salt and O-methylated via its silver salt. Oxidation of isatins with hydrogen peroxide in methanolic sodium methoxide yields methyl anthranilates (81AG(E)882>. In moist air, O-methylisatin (191) forms methylisatoid (192). Isatin forms normal carbonyl derivatives (193) with ketonic reagents such as hydroxylamine and phenylhydrazine and the reactive 3-carbonyl group also undergoes aldol condensation with active methylene compounds. Isatin forms a complex derivative, isamic acid (194), with ammonia (76JCS(P1)2004). 

The structure of febrifugine (the famous Chan San alkaloid known since 200 b.c.) has been completely elucidated, but that of the isomer isofebrifugine which occurs with it is still in some doubt. All evidence points to the semiketal structure (52) and, although it is readily converted to febrifugine, it does not react with ketonic reagents. 

Very high levels of induced diastereoselectivity are also achieved in the reaction of aldehydes with the titanium enolate of (5)-l-rerr-butyldimethylsiloxy-1-cyclohexyl-2-butanone47. This chiral ketone reagent is deprotonated with lithium diisopropylamide, transmetalated by the addition of triisopropyloxytitunium chloride, and finally added to an aldehyde. High diastereoselectivities are obtained when excess of the titanium reagent (> 2 mol equiv) is used which prevents interference by the lithium salt formed in the transmetalation procedure. Under carefully optimized conditions, diastereomeric ratios of the adducts range from 70 1 to >100 1. 

Entry Aldehyde J or ketone Reagent Adduct (% Yield) Rearrangement method Cyclobutanone (% Yield) Ref. 

Constitution of the Esters of the (3-Ketocarboxylic Acids and of the P-Diketones.—Ethyl acetoacetate is taken as example. It reacts like a ketone with phenylhydrazine, bisulphite, and other ketone reagents on the other hand it shows an acid reaction, it dissolves in alkalis, and gives the colour reaction with ferric chloride characteristic of ends and also of phenols. From this double behaviour it was formerly concluded that it was either purely ketonic or purely enolic and that the reactions in the other form were to be attributed to a rearrangement caused by the reagents used. The true state of affairs was first disclosed by... 

Reagent % Yield ketone reagent % Yield ketone ... 

In principle, a number of different types of acetal or ketal might be produced. In this section, we want to exemplify a small number of useful reactions in which two of the hydroxyl groups on the sugar are bound up by forming a cyclic acetal or ketal with a snitable aldehyde or ketone reagent. Aldehydes or ketones react with 1,2- or 1,3-diols under acidic conditions to form cyclic acetals or ketals. If the diol is itself cyclic, then the two hydroxyl groups need to be cA-oriented to allow the thermodynamically favourable fused-ring system to form (see Section 3.5.2). Thus, dx-cyclohexan-1,2-diol reacts with acetone to form a cyclic ketal, a 1,2-O-isopropylidene derivative usually termed, for convenience, an acetonide. 

The sodium bisulfite addition compounds must have a free (or potentially free) ketone-type carbonyl group, since they readily form derivatives with typical ketone reagents such as semicarbazide and 2,4-dinitrophenylhydrazine.174 Decomposition of these derivatives with alkali gives the corresponding adrenochrome derivatives e.g., adrenochrome monosemicarbazone would be obtained from the semicarbazone of the adrenochrome-sodium bisulfite complex.174 If one accepts Tse and Oesterling s formulation of the adrenochrome-sodium bisulfite complex, the semicarbazone would probably have a basically similar structure (i.e. 82). This type of structure is more... 

One of the most characteristic reactions of the aminochromes is the ready formation of mono-derivatives with typical ketone reagents, e.g. semicarbazide, phenylhydrazine, etc. A relatively large number of derivatives of this nature have been prepared because of then-reported hemostatic activity (cf. refs. 2 and 3). Compounds of this type that had been described in the literature prior to December 1959 are listed in a previous review (Heacock3). Some further examples of this class of compounds have been described recently. They are N-ethylnoradrenochrome semicarbazone (84) (orange-red needles, m.p.180 215°)65 7-iodoadrenochrome methyl ether semicarbazone... 

Pyridine-, pyran- and azine-thiones behave as cyclic thioamides or thioesters and show their typical reactions. Thus, they react with electrophiles at the sulfur atom [as exemplified in (i)-(iv)], and with nucleophiles including the typical ketonic reagents at the thione carbon atom [as exemplified in (vi)-(viii)]. 

Carbonyl groups not adjacent to a heteroatom are less stabilized by resonance and react with the relatively weakly nucleophilic ketonic reagents. If carbonyl groups of both types are present, as in... 

Platinum-alkylperoxo and -hydroperoxo complexes are much less effective ketonization reagents than their palladium analogs. The platinum-hydroperoxide complex generated by protonation of Pt(PPh3)202 as in equation (90) was found to be inactive,133 as well as Pt(CF3)(OOH)(depe) obtained from the reaction of H202 with the corresponding hydroxo complex.265... 

Used for the precolumn preparation of fluorescent derivatives of aldehydes and ketones reagent suggested to be especially useful because of its application on the microlevel, for the analysis and identification of carbonyl compounds in smog, polluted air, and biochemical and pharmaceutical mixtures reagent does not appear to be useful for analysis of sugars derivatives are fluorescent in the UV as solids and in solution References 21, 22... 

Whilst in some cases near-stoichiometric amounts of reagents can be used [16], the excess (5-10 equiv.) of ketone reagent is preconceived in order to ensure convenient kinetics and conversion. Reactions can be run typically at room temperature [20] in a polar aprotic solvent such as CHC13, or in THF or i-PrOH. The presence of water was noted to be beneficial in some cases [21]. In ionic liquids, such as in [bmim]BF4, a low (5 mol%) catalyst concentration can be applied, while the enantioselectivity of the alkylation is modest in this solvent [22]. The ionic liquid-derived hybrid catalyst 10, used neat with a small amount of trifluoroacetic acid (TFA) as co-catalyst, affords quantitatively 4, though in a remarkably high dr syn/anti = 99/1) and ee (99%). It should be noted that this catalyst can easily be recovered by extraction, and re-used without loss of activity. 

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