Butene oxidative carbonylation

Metathesis is the rupture and reformation of carbon-carbon bonds—for example, of propylene into ethylene plus butene. Catalysts are oxides, carbonyls, or sulfides of Mo, W, or Re. 

Solid catalysts for the metathesis reaction are mainly transition metal oxides, carbonyls, or sulfides deposited on high surface area supports (oxides and phosphates). After activation, a wide variety of solid catalysts is effective, for the metathesis of alkenes. Table I (1, 34 38) gives a survey of the more efficient catalysts which have been reported to convert propene into ethene and linear butenes. The most active ones contain rhenium, molybdenum, or tungsten. An outstanding catalyst is rhenium oxide on alumina, which is active under very mild conditions, viz. room temperature and atmospheric pressure, yielding exclusively the primary metathesis products. 

Carbenes or carbenoids have also been reported to deoxygenate epoxides. To generate these species, dimethyl diazomalonate/rhodium(II) acetate and 9-diazofluorene 44 have been employed both reagents show high stereoselectivity. For example, ciJ-2-butene oxide is converted to cir-alkene with more than 93% retention under irradiation (350 nm) using 9-diazofluorene, and functional groups, such as carbonyl, can survive using diazomalonate and rhodium(II) acetate (equation 49). 

The oxidative carbonylation of cw-2-butene in the presence of methanol, catalytic amounts of PdCl2, and stoichiometric quantities of CUCI2 under a reaction pressure of about 3 bar yields a racemic mixture of threo- and erythro- methyl 3-methoxy-2-methylbutyrate (ratio of the isomers, 87 13). Under comparable conditions, but in the presence of sodium acetate, twofold carbonylation is observed, giving m 50-dimethyl 2,3-dimethylsuccinate as the only reaction product. Starting from rra 5-2-butene, in an analogous manner threo- and erythro-met y 3-methoxy-2-methylbutyrates are again obtained, but in a different ratio of the isomers (40 60). If sodium acetate is added, racemic dimethyl R,S)-2,3-dimethylsuccinate is the sole product [7-9]. 

The future of the commercial acetaldehyde processes mainly depends on the availability of cheap ethylene. Acetaldehyde has been replaced as a precursor for 2-ethylhexanol ( aldol route ) or acetic acid (via oxidation cf. Sections 2.1.2.1 and 2.4.4). New processes for the manufacture of acetic acid are the Monsanto process (carbonylation of methanol, cf. Section 2.1.2.1), the Showa Denko one-step gas-phase oxidation of ethylene with a Pd-heteropolyacid catalyst [75, 76], and Wacker butene oxidation [77]. Other outlets for acetaldehyde such as pentaerythritol and pyridines cannot fill the large world production capacities. Only the present low price of ethylene keeps the Wacker process still attractive. 

Selectivities to various isomers are more difficult to predict when metal oxides are used as catalysts. ZnO preferentially produced 79% 1-butene and several percent of i7j -2-butene [624-64-6] (75). CdO catalyst produced 55% 1-butene and 45% i7j -2-butene. It was also reported that while interconversion between 1-butene and i7j -2-butene was quite facile on CdO, cis—trans isomeri2ation was slow. This was attributed to the presence of a TT-aHyl anion intermediate (76). High i7j -2-butene selectivities were obtained with molybdenum carbonyl encapsulated in 2eohtes (77). On the other hand, deuteration using H1O2 catalyst produced predominantly the 1,4-addition product, trans-2-huX.en.e-d2 with no isotope scrambling (78). 

In 1909, Patemo and Chieffi noted that mixtures of tri- or tetra-substituted olefins and aldehydes formed trimethylene oxides when exposed to sunlight. Biichi later repeated Patemo s experiments by irradiating 2-methyI-2-butene in the presence of benzaldehyde, butyraldehyde, or aeetophenone and rigorously purifying and identifying the resulting products. The reaction thus bears the name of its two primary pioneers and has come to represent any photo-catalyzed [2 + 2] electrocyclization of a carbonyl and an alkene. 

Acetic acid is obtained from different sources. Carbonylation of methanol is currently the major route. Oxidation of butanes and butenes is an important source of acetic acid, especially in the U.S. (Chapter 6). It is also produced by the catalyzed oxidation of acetaldehyde ... 

Volume 75 concludes with six procedures for the preparation of valuable building blocks. The first, 6,7-DIHYDROCYCLOPENTA-l,3-DIOXIN-5(4H)-ONE, serves as an effective /3-keto vinyl cation equivalent when subjected to reductive and alkylative 1,3-carbonyl transpositions. 3-CYCLOPENTENE-l-CARBOXYLIC ACID, the second procedure in this series, is prepared via the reaction of dimethyl malonate and cis-l,4-dichloro-2-butene, followed by hydrolysis and decarboxylation. The use of tetrahaloarenes as diaryne equivalents for the potential construction of molecular belts, collars, and strips is demonstrated with the preparation of anti- and syn-l,4,5,8-TETRAHYDROANTHRACENE 1,4 5,8-DIEPOXIDES. Also of potential interest to the organic materials community is 8,8-DICYANOHEPTAFULVENE, prepared by the condensation of cycloheptatrienylium tetrafluoroborate with bromomalononitrile. The preparation of 2-PHENYL-l-PYRROLINE, an important heterocycle for the synthesis of a variety of alkaloids and pyrroloisoquinoline antidepressants, illustrates the utility of the inexpensive N-vinylpyrrolidin-2-one as an effective 3-aminopropyl carbanion equivalent. The final preparation in Volume 75, cis-4a(S), 8a(R)-PERHYDRO-6(2H)-ISOQUINOLINONES, il lustrates the conversion of quinine via oxidative degradation to meroquinene esters that are subsequently cyclized to N-acylated cis-perhydroisoquinolones and as such represent attractive building blocks now readily available in the pool of chiral substrates. 

The same authors (77) also investigated the Michael addition of nitromethane to a,/l-unsaturated carbonyl compounds such as methyl crotonate, 3-buten-2-one, 2-cyclohexen-l-one, and crotonaldehyde in the presence of various solid base catalysts (alumina-supported potassium fluoride and hydroxide, alkaline earth metal oxides, and lanthanum oxide). The reactions were carried out at 273 or 323 K the results show that SrO, BaO, and La203 exhibited practically no activity for any Michael additions, whereas MgO and CaO exhibited no activity for the reaction of methyl crotonate and 3-buten-2-one, but low activities for 2-cyclohexen-l-one and crotonaldehyde. The most active catalysts were KF/alumina and KOH/alumina for all of the Michael additions tested. 

Conjugate addition of methanol to a,/l-unsaturated carbonyl compounds forms a new carbon-oxygen bond to yield valuable ethers (Scheme 26). Kabashima et al. (12) reported the conjugate addition of methanol to 3-buten-2-one on alkaline oxides, hydroxides, and carbonates at a temperature of 273 K. The activities of the catalyst follow the order alkaline earth metal oxides > alkaline earth metal hydroxides > alkaline earth metal carbonates. All alkaline earth metal oxides exhibited high catalytic activities and, as in alcohol condensations and nitroaldol reactions, their catalytic activities were not much affected by exposure to CO2 and air. 

In oxidation studies it has usually been assumed that thermal decomposition of alkyl hydroperoxides leads to the formation of alcohols. However, carbonyl-forming eliminations of hydroperoxides, usually under the influence of base, are well known. Of more interest, nucleophlic rearrangements, generally acid-catalyzed, have been shown to produce a mixture of carbonyl and alcohol products by fission of the molecule (6). For l-butene-3-hydroperoxide it might have been expected that a rearrangement (Reaction 1) similar to that which occurs with cumene hydroperoxide could produce two molecules of acetaldehyde. 

There are some cases where both types of photocycloaddition take place. For example, cinnamaldehyde and crotonaldehyde yield, upon irradiation with 2-methyl-2-butene, both the oxetane and the cyclobutane products.26 In marked contrast, mesityl oxide, as similar as it would appear to be to crotonaldehyde (Table I), is stable to irradiation in the presence of both isobutylene and isopropanol.37,74 These differences in reactivity of a,/9-unsaturated carbonyl compounds have been attributed to conformational (that is, s-cis or s-trans) differences.74... 

Steam may have a positive effect on the activity according to Komaro-vskii et al. [179], A doubling of the reaction rate was observed by adding up to 20% steam to the oxidation of a mixture of n-butenes in a flow reactor over a Bi/Mo catalyst of unknown composition at 420—480°C. The same authors [179] also studied the influence of the oxygen concentration, which was found to have no effect on the kinetics at 02/butene > 0.4. Furthermore, a rather complex set of kinetic equations was derived to describe side reactions (isomerization, and formation of carbonyls, acids and furan). 

Silyl-l,3-dienes undergo anodic methoxylation in methanol to give 1,4-addition products with an allylsilane structure as intermediates. Therefore, they are further oxidized to give l,l,4-trimethoxy-2-butene derivatives as the final products. The products are easily hydrolyzed to provide the corresponding y-methoxy-a, /t-unsaUirated aldehydes. Since 1-trimethylsilyl-l,3-dienes are readily prepared by the reaction of the anion of l,3-bis(trimethylsilyl)propene with aldehydes or ketones, l,3-bis(trhnethylsilyl)propene offers a, /i-formylvinyl anion equivalent for the reaction with carbonyl compounds (equation 15)16. 

The major conventional processes for the production of acetic acid include the carbonylation of methanol (originally developed by Monsanto, and now carried out by several companies, such as Celanese-ACID OPTIMIZATION, BP-CATIVA, etc.), the liquid-phase oxidation of acetaldehyde, still carried out by a few companies, and the liquid-phase oxidation of n-butane and naphtha. More recent developments include the gas-phase oxidation of ethylene, developed by Showa Denko K.K., and the liquid-phase oxidation of butenes, developed by Wacker [2a],... 

Under similar conditions, the photocatalytic oxidation of 2-or 3-methyl-l-butene and of 2-methyl-2-butene over Ti(>2 yielded carbonyl compounds as partial oxidation products (18). However, the selectivity to a particular aldehyde or ketone was reduced by cleavages not only of the double bond but also of the Cg-Cy bond. 

Fig. 15.47. Solvent dependence of the decomposition of the symmetric primary ozonide formed in the ozonolysis of tetramethylethene (2,3-di-methyl-2-butene). The initially formed carbonyl oxide forms a hydroperoxide in methanol, while it dimerizes to give a 1,2,4,5-tetroxane in CH2C12.

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