Acetone reactions acid-catalysis

Erom natural sources the (R)-enantiomer of ( )-a-ionone is detected with high enantiomeric purity (much more than 99%) hence, the authenticity of ( )-a-ionone is mostly proved via enantio-GC applications [27,65-67]. In the majority of cases synthetic ionones are produced via pseudoionone, prepared by base-catalysed condensation of citral with acetone. After acidic catalysis (using 85% phosphoric acid or concentrated sulphuric acid), this reaction yields racemic ( )-a-ionone and ( )-/l-ionone [68]. 

As a result of their potent pharmacological activity, 4-aryl-1,2,3,4- tetrahydroisoquinolines have attracted numerous synthetic efforts. Treatment of ( S)-1 with acetone under acid catalysis generates ( S)-( + )-2,2-dimethyl-5-phenyl-l,3-dioxolan-4-one (55) in 80% yield. Reaction of 55 with methylamine followed by lithium aluminum hydride reduction of the resultant amide provides ( S)-(+ )-A-methylamino-l-phenylethanol [(5)-( + )-halostachine] (56). N-... 

A similar protecting group, called an acetonide, can block reaction at the 2 and 3 oxygens of a nucleoside. This protected derivative is formed by the reaction of the nucleoside with acetone under acid catalysis. From this information, draw the protected product formed by the reaction. 

Ketones with labile hydrogen atoms undergo enol acetylation on reaction with ketene. Strong acid catalysis is required. If acetone is used, isoptopenyl acetate [108-22-5] (10) is formed (82—85). Isopropenyl acetate is the starting material for the production of 2,4-pentanedione (acetylacetone) [123-54-6] (11). 

The Hock process includes the oxidation of cumene by air to hydroperoxides using large bubble columns and the cleavage of the hydroperoxide via acid catalysis, which is reaction [OS 82]. This process is used for the majority of world-wide phenol production and, as a secondary product, also produces large quantities of acetone [64]. Phenol is used, e.g., for large-scale polymer production when reacted in a polycondensation with formaldehyde. 

Hydride transfer from [(bipy)2(CO)RuH]+ occurs in the hydrogenation of acetone when the reaction is carried out in buffered aqueous solutions (Eq. (21)) [39]. The kinetics of the reaction showed that it was a first-order in [(bipy)2(CO)RuH]+ and also first-order in acetone. The reaction proceeds faster at lower pH. The proposed mechanism involved general acid catalysis, with a fast pre-equilibrium protonation of the ketone followed by hydride transfer from [(biPy)2(CO)RuH]+. 

The original Garner preparation3 of 5 involves the conversion of serine into the protected methyl ester 3 and controlled reduction of the latter by DIBAL. The reaction sequence employed for the preparation of 3 involves the protection of the amino acid as N-Boc derivative using di-tert-butyl dicarbonate, esterification with methyl iodide or diazomethane, and acetonization with 2,2-dimethoxypropane under acid catalysis. The N-Boc methyl serinate and the ester 3 require purification by vacuum distillation or chromatography. In a modification to this procedure reported by McKillop,2 the esterification reaction of serine is carried out first by methanol/acetyl chloride. The resulting ester is then converted into the N-Boc derivative 2 with di-tert-butyl dicarbonate and the latter transformed into 3 by acetonization. This procedure avoids... 

The mechanism of the reaction has been studied extensively, and has been shown to vary with the reaction conditions (64AHC(3)285). Cyanuric chloride is insensitive to both acid catalysis and autocatalysis, but the 2,4-dichloro (55) and 2-chloro derivatives (56) exhibit both acid catalysis and autocatalysis on solvolysis in ethanol-acetone solutions. 

One of the most spectacular and useful template reactions is the Curtis reaction , in which a new chelate ring is formed as the result of an aldol condensation between a methylene ketone or inline and an imine salt. The initial example of this reaction was the formation of a macrocyclic nickel(II) complex from tris(l,2-diaminoethane)nickel(II) perchlorate and acetone (equation 53).182 The reaction has been developed by Curtis and numerous other workers and has been reviewed.183 In mechanistic terms there is some circumstantial evidence to suggest that the nucleophile is an uncoordinated aoetonyl carbanion which adds to a coordinated imine to yield a coordinated amino ketone (equation 54). If such a mechanism operates then the template effect is largely, if not wholly, thermodynamic in nature, as described for imine formation. Such a view is supported by the fact that the free macrocycle salts can be produced by acid catalysis alone. However, this fact does not... 

Acid catalysis—hydrolysis. Several series of alkylsilane esters were studied to determine the effect of silane structure on the hydronium ion catalyzed hydrolysis reaction. The hydronium ion catalyzed hydrolysis rate constants for a series of alkyl tris-(2-methoxyethoxy)silanes in aqueous solution were used to define the modified Taft equation log(A /Ah ) = 0.39a + 1.06ES, where Ho is the rate of hydrolysis for methyl tris-2-(methoxyethoxy)silane [42], The hydronium ion catalyzed hydrolysis rate constants and the reaction half-lives are reported in Table 2. In a similar manner, the hydronium ion catalyzed hydrolysis rate constants for a series of trialkylalkoxysilanes in 55% aqueous acetone were used to obtain the modified Taft equation log(/cH//cHo) = -0.37 a + 2.48 E where kHo is the rate of hydrolysis for trimethylalkoxy-silane. 

Addition of primary amines to carbonyl groups has been the subject of extensive study, notably by Jencks and co-workers.91 The most striking feature of these reactions is the characteristic maximum in the graph of reaction rate as a function of pH.92 Figure 8.10 illustrates the observations for the reaction of hydroxylamine with acetone. It is also found that the sensitivity of rate to acid catalysis,93 and to substituent effects,94 is different on either side of the maximum in the pH-rate curve. These phenomena may be understood in terms of the two-step nature of the reaction. In acetal formation, we saw in Section 8.3 that the second step is rate-limiting in the overall process, and it is relatively easy to study the two steps separately here, the rates of the two steps are much more closely balanced, so that one or the other is rate-determining depending on the pH. 

A widely studied example of this kind is the synthesis of methyl isobutyl ketone (MIBK, used as a solvent for inks and lacquers) from acetone. The former was previously prepared from the latter through a catalytic three-step process base-catalysed production of 4-hydroxy-4-methylpentan-2-one, acid dehydration into mesityloxide (MO), then hydrogenation of MO on a Pd catalyst. Since acetone aldolization occurs through acid catalysis as shown over a H-MFI zeolite at 433 K (MO is the main reaction product, the aldolization product being rapidly dehy-drated[5]), it is possible, by associating with the acid catalyst a hydrogenation phase,... 

Acetonides [383,384] and siliconides [385,386] are prepared by the reactions of neighbouring hydroxyl groups, e.g., in positions 16,17 and 17,21, with acetone or dimethylchlorosilane. The reaction with acetone proceeds under acid catalysis with hydrogen chloride or TMCS, as follows. Steroids are dissolved in 10 ml of freshly distilled acetone and 100 n 1 of TMCS are added. The mixture is agitated at room temperature for 2 h, 1 ml of 1 N sodium hydroxide solution is added and the solvent is evaporated at... 

Desimoni and Righetti have been thoroughly investigating the effect of solvents, acid catalysis and salts on hetero Diels-Alder and ene reactions of 1-oxa-1,3-butadienes for a long time [ 154-156]. Recently, for the cycloaddition of 2-154 and ethyl vinyl ether 2-83 in the presence of lithium perchlorate in different solvents as diethyl ether, acetonitrile, acetone, methanol, iso-propanol to give... 

A material such as Na°/NaY catalyzes the aldol condensation of acetone, to form mesityl oxide and eventually isophorone. Another strong base catalyzed reaction is the side chain alkylation of toluene with ethylene. In contrast with acid catalysis, side chain reaction is strongly preferred over ring alkylation. With a Na°/NaX in the gas phase at 473 K, toluene reacts to give n-propylbenzene (66%) and the dialkylated product, 3-phenylpentane (32%) (41). 

The aldol condensation can also be brought about with acid catalysis. There are many aldol-like reactions which involve an aldehyde or ketone. However, the word aldol is a common name for the product of these reactions. Generally, the word aldol is used to refer to any P-hydroxyaldehyde or (3-hydroxyketone. For example, treatment of acetone with a base results in the aldol reaction. The product, -hydroxyketone 3.14, is separated from the reaction mixture as it is formed. 

DISN adds to 2,2-dimethoxypropane in the presence of sulfuric acid as catalyst to give 2,2-dimethyl-4,5-dicyanoisoimidazole (9) in 80% yield. Reaction of (I) under oxalic acid catalysis also gives (9) in 80% yield. Reaction with acetone itself gives (9) in low... 

Gi increases with increasing positive charge, and a recent detailed analysis of catalytic effects of uncharged bases in the decomposition of nitramide shows that there is a dependence on the structure of the base (Bell and Wilson, 40 Bell, 41). For the mutarotation of glucose at 18°, Ga = 33 X 10 and y = 0.40. For the more accurate results on the acid catalysis of the acetone-iodine reaction at 25°, Gi and x are 120 X lO" and 0.62, respectively, in the equation... 

The aldol reaction in carbonyl compounds has its equivalents in 7i-electron deficient heterocycles. In the carbanion approach, lithiated acetophenone added rapidly and regioselectively to 1-substituted 2-pyrimidinones to form the 3,4-dihydro isomer (279) (Scheme 45) <85ACS(B)195>. The adducts are readily oxidized to their aromatic equivalents (280) by DDQ. With the lithium enolate of mesityl oxide, however, equal amounts of the two dihydro isomers were formed <88JOM(338)34l>. In highly 7i-electron deficient heterocyclic systems, aldol reactions will also take place under the influence of acid catalysis such as in the addition of acetone to the pyrimidinone (281) the product is fully conjugated (282) after DDQ dehydrogenation <79ACS(B)150>. 

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