Ketones isomerism

Several triazinyl ketones isomerize to 4-acetamidopyrimidines. TTiis is seen in the C-acylation of 2,4,6-trimethyl-l,3,5-triazine (708) with benzoyl chloride in the presence of sodium amide to give the ketone (709) which undergoes a Dimroth-like rearrangement in boiling water to afford A-(2-methyl-6-phenylpyrimidin-4-yl)acetamide (710) it can be seen that the acylating agent determines the identity of the 6-substituent 64JHC145). 

Photochemical cyclohex-2-enone bicyclo (3.1.0)hexan-2-one rearrangement, 320 Photochemical a-cyclopropyl ketone isomerization, 313... 

A ketone isomeric with irone has been isolated from oil of cassie flowers. It is possible that this is /9-ionone, but its identity has not yet been established. 

The alcohols are intermediates in the formation of ketones. Isomerization of the products is not observed. Hydroxylation at the 2-position is favored over that at the 3-position, and the latter is preferred over hydroxylation at the 4-position. Solubility and concentration in the reaction medium, intrazeolite diffusion of the reactants, steric hindrance at the reactive carbon center, and C-H bond strength influence the reactivity and H202 selectivity (Table XXIV). The advantage of the large-pore Ti-beta over TS-1 in the oxidation of bulky alkane molecules is shown by the results in Table XXV. 

Alkyl aryl ketones isomerize in reasonable yields to 1-phenylcyclobutan-l-ols. The well-known conversion of butyl phenyl ketone to a 1 1 mixture of diastereomeric 2-methyl-l-phenylcy-clobutan-l-ols has been described as a laboratory student experiment.9... 

P-Diketonesfrom %/i-epoxy ketones. 2 In the presence of this Pd(0) complex a,/ -epoxy ketones isomerize to /3-dikelones. An added ligand is usually necessary to avoid precipitation of palladium. The most satisfactory adjunct is l,2-bis(diphenyl-phosphino)ethane (dpe). The reaction is conducted in toluene at 80-140° for 10 100 hours. The isomerization is facile with strained epoxides it is sluggish with epoxides bearing an a-alkyl group. 

As a comparison of the enthalpies of formation of isomeric aldehydes and ketones shows, the disubstituted carbonyl compounds (ketones) are more stable than the monosubstituted carbonyl compounds (aldehydes), analogous to the stability order for the corresponding 1,1-disubstituted ethenes and the 1-n-alkenes. For the three aldehyde/methyl ketone isomeric pairs (nc = 3-5), initially it seems that the enthalpies of isomerization are fairly constant. However, if the interpolated value for pentanal is used, the trend is clearly that of more negative enthalpy of isomerization with increasing c(g) —31.7, —33.9, —34.5 kJmol-1. The non-constant enthalpies are expected because the slopes, ag, in Table 4 are quite different for aldehydes and ketones. The greater contribution to the isomerization enthalpy differences comes from the methyl ketone which is more stabilized than the aldehyde by an additional —CH2— group. The enthalpies of isomerization of the corresponding alkenes are much less exothermic (—6.1 0.8 kJmol-1) than those of the carbonyl compounds. 

In the reaction of allylic organozinc reagents with carbonyl derivatives (e.g., diisobutyl ketone), isomerization of the branched product (XXX) occurs to the thermodynamically more stable linear product (XXXI) (333). The ratio of linear to branched alcohol increases with longer reaction time, and this was taken as evidence that the branched alco-... 

Functional group isomerism, e.g. in alcohols and ethers, aldehydes and ketones. Isomerism in aromatic compounds. 

Ma and Zhang reported palladium-catalyzed isomerization of the alkylidenecyclopropyl ketone 249.153 In the presence of a catalytic amount of Pd(CH3CN)2Cl2 and 2 equiv of Nal, the alkylidenecyclopropyl ketone isomerized to the corresponding 3-furyl ester 250 (Scheme 81). By contrast, in the absence of Nal, the 4//-pyran 251 was obtained selectively. The reaction of 249 with Nal proceeds through the cyclopropyl-palladium intermediate 252, while in the absence of Nal the formation of the cyclopropylcarbinylpalla-dium 253 takes place. 

Alkene isomerization. Allylic alcohols are converted to saturated ketones. Isomerization of the allyl group of (V,C>-acetals paves way to a synthesis of 2-(a-amidoalkyOpropanals. ... 

In uns3mmetrical dialkyl ketones, isomeric enolate ions can be formed. The equilibrium concentration of two possible enolate ions and the selectivity of the attacking Ar" radical largely determine the distribution of two possible a-arylated products [9]. For example, Ph" radical coupled to the most substituted position of the enolate ion of the 2-butanone gives mainly product 30 [21,31]. 

The Q -(methyldiphenylsilyl) ketones isomerize to the corresponding silyl enol ether regioselectively simply by mild thermolysis at about 150 °C (eq 6). This reaction can also be done in a stereoselective fashion to give the (Z)-enol silyl ether when the thermolysis is carried out in acetonitrile (eq 7). ... 

Enol-ketone Isomerization may act as a Trigger for Enediyne Activation... 

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