Mesityl oxide reactions

Catalyst %Se Aldol %Se Mesityl Oxide Reaction rate (xlO moEg s) % Conversion... 

The advantage of using a catalyst is obvious. When one reactive center of the keto compound is substituted by a methyl or phenyl group (Rz) the catalyst effect is more enhanced. Mesityl oxide (Rj = Rz = R3 = Me) requires very high pressure and efhcient lanthanide catalysis. This reaction involving a sterically congested unsaturated ketone is a prominent example emphasizing the requirement of biactivation to overcome steric hindrance. It should be added that, apart from the mesityl oxide reaction, a modest pressure (300 MPa) is sufficient to induce reactivity in these catalyzed reactions which were shown to proceed only at pressures in excess of 1200 MPa in an uncatalyzed version [33]. 

Assemble a 250 ml. three-necked flask, fitted with a stirrer, a reflux condenser and a dropping-funnel, as in Fig. 22(A) and (j), p. 43, or Fig. 23(c), p. 46 (or a two-necked flask, with the funnel fitted by a grooved cork (p. 255) to the top of the condenser). Place 40 ml. of ethanol in the flask, and then add 2-3 g. of sodium cut into small pieces. When all the sodium has dissolved, heat the stirred solution on the water-bath, and run in from the funnel 17 g. (17 ml.) of ethyl malonate and then (more slowly) io-2 g. (12 ml.) of mesityl oxide, the reaction-mixture meanwhile forming a thick slurry. Boil the stirred mixture under reflux for i hour, and then add a solution of 10 g. of sodium hydroxide in 50 ml. of water, and continue boiling the pale honey-coloured solution for ij hours more. 

Some unsaturated ketones derived from acetone can undergo base- or acid-catalyzed exothermic thermal decomposition at temperatures under 200°C. Experiments conducted under adiabatic conditions (2) indicate that mesityl oxide decomposes at 96°C in the presence of 5 wt % of aqueous sodium hydroxide (20%), and that phorone undergoes decomposition at 180°C in the presence of 1000 ppm iron. The decomposition products from these reactions are endothermic hydrolysis and cleavage back to acetone, and exothermic aldol reactions to heavy residues. 

In the three-step process acetone first undergoes a Uquid-phase alkah-cataly2ed condensation to form diacetone alcohol. Many alkaU metal oxides, metal hydroxides (eg, sodium, barium, potassium, magnesium, and lanthanium), and anion-exchange resins are described in the Uterature as suitable catalysts. The selectivity to diacetone alcohol is typicaUy 90—95 wt % (64). In the second step diacetone alcohol is dehydrated to mesityl oxide over an acid catalyst such as phosphoric or sulfuric acid. The reaction takes place at 95—130°C and selectivity to mesityl oxide is 80—85 wt % (64). A one-step conversion of acetone to mesityl oxide is also possible. 

Finally, selective hydrogenation of the olefinic bond in mesityl oxide is conducted over a fixed-bed catalyst in either the Hquid or vapor phase. In the hquid phase the reaction takes place at 150°C and 0.69 MPa, in the vapor phase the reaction can be conducted at atmospheric pressure and temperatures of 150—170°C. The reaction is highly exothermic and yields 8.37 kJ/mol (65). To prevent temperature mnaways and obtain high selectivity, the conversion per pass is limited in the Hquid phase, and in the vapor phase inert gases often are used to dilute the reactants. The catalysts employed in both vapor- and Hquid-phase processes include nickel (66—76), palladium (77—79), copper (80,81), and rhodium hydride complexes (82). Complete conversion of mesityl oxide can be obtained at selectivities of 95—98%. 

Ma.nufa.cture. Mesityl oxide is produced by the Hquid-phase dehydration of diacetone alcohol ia the presence of acidic catalysts at 100—120°C and atmospheric pressure. As a precursor to MIBK, mesityl oxide is prepared ia this manner ia a distillation column ia which acetone is removed overhead and water-saturated mesityl oxide is produced from a side-draw. Suitable catalysts are phosphoric acid (177,178) and sulfuric acid (179,180). The kinetics of the reaction over phosphoric acid have been reported (181). 

Mesityl oxide can also be produced by the direct condensation of acetone at higher temperatures. This reaction can be operated ia the vapor phase over 2iac oxide (182), or 2iac oxide—2irconium oxide (183), or ia the Hquid phase over cation-exchange resia (184) or 2irconium phosphate (185). Other catalysts are known (186). 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

Although the selectivity is high, minor amounts of by-products can form by dehydration, condensation, and oxidation, eg, propylene [115-07-17, diisopropyl ether, mesityl oxide [141-79-7] acetaldehyde [75-07-0], and propionaldehyde [123-38-6]. Hydrotalcites having different Al/(A1 + Mg) ratios have been used to describe a complete reaction network for dehydrogenation (17). This reaction can also be carried out in the Hquid phase. 

A number of dihydroquinolines have been prepared by treating aniline derivatives with acetone or mesityl oxide in the presence of iodine. In these cases aromatization to the fully unsaturated quinoline would require the loss of methane, a process known as the Riehm quinoline synthesis. Such Skraup/Doebner-von Miller-type reactions are often low yielding due to large amounts of competing polymerization. For example, aniline 37 reacts with mesityl oxide to give dihydroquinolines 39, albeit in low yield. ... 

An interesting application of this reaction was the use of macro-molecular anhydrides, namely, styrene-maleic anhydride or vinyl acetate-maleic anhydride copolymers in the presence of perchloric acid as catalyst, these copolymers acylate mesityl oxide or d rpnone to macromolecular pyrylium salts which, with aryl substituents, are fluorescent.No crystalline products could be obtained from succinic anhydride because of the solubility and ease of decarboxylation. 

Besides acetophenone, this reaction was also applied to p-chloro- andp-methoxyacetophenone, and even to an aliphatic ketone, acetone (although the yield was stated to be only half as large as that obtained from mesityl oxide, i.e., less than 30%, Dorofeenko and co-workers reported a 45% yield of 2,4,6-trimethylpyrylium perchlorate from acetone, acetic anhydride, and perchloric acid), and is the standard method for preparing pyrylium salts with identical substituents in positions 2 and 4. The acylating agent may be an anhydride in the presence of anhydrous or hydrated ferric chloride, or of boron fluoride, or the acid chloride with ferric chloride.Schneider and co-workers ... 

V,7V-dimethylaminopyridme provides l-(2-methoxycarbonyl)ethoxy- (40,69%) and l-(2-methoxycarbonyl-l-methyl)ethoxytryptamine (41, 72%), respectively (Scheme 4). The conjugate addition to mesityl oxide proceeds successfully as well, giving iVb-acetyl-1-(1, l-dimethyl-3-oxo)butoxytryptamine (42,49%), while the reaction with methyl 3-methylcrotonate affords 43 in a miserable yield (1.6%). Addition to acrolein results in failure, and 44 is not yet obtained. 

Compound 68 can also be obtained by an acid-catalyzed cyclization of 42, which was prepared by the Michael addition reaction of 39 to mesityl oxide as shown in Section IV.A. As for the product 69, the presence of the tosyloxy group at the 5 position instead of the 6 position is determined, utilizing the anisotropy effect of the 1-acetyl group to the C-7 proton, by comparing its H NMR spectrum with that of 70, obtained in 69% yield by the treatment of 69 with NaH and AcCl. 

The well-known condensation between 2-furaldehyde and acetone in a basic medium yields what is usually called furfurylidene acetone monomer composed of a mixture of 2-furfurylidene methyl ketone, di-2-furfurylidene ketone, mesityl oxide and other oligomers derived from further condensation reactions135. This mixture is then polymerized by the action of an acidic catalyst in the first phase of the reaction a polymer of low molecular weight is produced which on further treatment cross-links to a black insoluble and heat-resistant material136. ... 

Purely parallel reactions are e.g. competitive reactions which are frequently carried out purposefully, with the aim of estimating relative reactivities of reactants these will be discussed elsewhere (Section IV.E). Several kinetic studies have been made of noncompetitive parallel reactions. The examples may be parallel formation of benzene and methylcyclo-pentane by simultaneous dehydrogenation and isomerization of cyclohexane on rhenium-paladium or on platinum catalysts on suitable supports (88, 89), parallel formation of mesityl oxide, acetone, and phorone from diacetone alcohol on an acidic ion exchanger (41), disproportionation of amines on alumina, accompanied by olefin-forming elimination (20), dehydrogenation of butane coupled with hydrogenation of ethylene or propylene on a chromia-alumina catalyst (24), or parallel formation of ethyl-, methylethyl-, and vinylethylbenzene from diethylbenzene on faujasite (89a). 

Histories . The Na salt was first isolated by the reaction of nitric oxide on acet (Ref 2) later the same worker found that the action of nitric oxide and Na hydroxide on any compd contg the acetyl group would give Na MEDNA [compds treated were mesityl oxide, methylisopropyl ketone, acetophenone, and ethyl dimethyl-... 

It is often said that the property of acidity is manifest only in the presence of a base, and NMR studies of probe molecules became common following studies of amines by Ellis [4] and Maciel [5, 6] and phosphines by Lunsford [7] in the early to mid 80s. More recently, the maturation of variable temperature MAS NMR has permitted the study of reactive probe molecules which are revealing not only in themselves but also in the intermediates and products that they form on the solid acid. We carried out detailed studies of aldol reactions in zeolites beginning with the early 1993 report of the synthesis of crotonaldehyde from acetaldehyde in HZSM-5 [8] and continuing through investigations of acetone, cyclopentanone [9] and propanal [10], The formation of mesityl oxide 1, from dimerization and dehydration of... 

The solid base catalysed aldol condensation of acetone was performed over a CsOH/Si02 catalyst using a H2 carrier gas. The products observed were diacetone alcohol, mesityl oxide, phorone, iso-phorone and the hydrogenated product, methyl isobutyl ketone. Deuterium tracer experiments were performed to gain an insight into the reaction mechanism. A mechanism is proposed. 

The aldol condensation of acetone to diacetone alcohol is the first step in a three-step process in the traditional method for the production of methyl isobutyl ketone (MIBK). This reaction is catalysed by aqueous NaOH in the liquid phase. (3) The second step involves the acid catalysed dehydration of diacetone alcohol (DAA) to mesityl oxide (MO) by H2S04 at 373 K. Finally the MO is hydrogenated to MIBK using Cu or Ni catalysts at 288 - 473 K and 3- 10 bar (3). 

The reaction mechanism is shown in Figure 4 and is adapted from work by Fiego et al. [9] on the acid catalysed condensation of acetone by basic molecular sieves. The scheme has been modified to include the hydrogenation of mesityl oxide to MIBK. The scheme begins with the self-condensation of acetone to form diacetone alcohol as the primary product. The dehydration of DAA forms mesityl oxide, which undergoes addition of an addition acetone to form phorone that then can cyclise, via a 1,6-Michael addition to produce isophorone. Alternatively, the mesityl oxide can hydrogenate to form MIBK. 

Amines, thiols, eOH (p. 226), etc., will also add to the 0-carbon atom of 0-unsaturated carbonyl compounds and esters, but the most important reactions of C=C—C=0 systems are in Michael reactions with carbanions reactions in which carbon-carbon bonds are formed. A good example is the synthesis of l,l-dimethylcyclohexan-3,5-dione (dimedone, 100) starting from 2-methylpent-2-ene-4-one (mesityl oxide, 101) and the carbanion 0CH(CO2Et)2 ... 

Reaction of iV-aminocarbonyl-2-phenylethylamines with mesityl oxide and 2-butenal afforded l,2,3,6,7,llb-hexahydro-477-pyrimido[6,l- ]isoquinoline-4-ones <2003MC278>. 9,10-Dimethoxy-l,2,3,6,7,llb-... 

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