Carbonylation methyl formate

Pt/AT-ethylpiperidine catalysts have also been described for methyl formate synthesis via methanol carbonylation. Methyl formate is itself a versatile... 

The Pd-catalyzed reductive carbonylation of methyl acetate with CO and H2 affords acetaldehyde. The net reaction is the formation of acetaldehyde from MeOH, CO, and H2P4]. Methyl formate (109) is converted into AcOH under CO pressure in the presence of Lil and Pd(OAc)2[95],... 

Formic acid is currently produced iadustriaHy by three main processes (/) acidolysis of formate salts, which are ia turn by-products of other processes (2) as a coproduct with acetic acid ia the Hquid-phase oxidation of hydrocarbons or (3) carbonylation of methanol to methyl formate, followed either by direct hydrolysis of the ester or by the iatermediacy of formamide. 

The carbonylation of methanol [67-56-1] to methyl formate ia the presence of basic catalysts has been practiced iadustriaHy for many years. Ia older processes for formic acid utili2ing this reactioa, the methyl formate [107-31-3] reacts with ammonia to give formamide [75-12-7] which is hydroly2ed to formic acid ia the preseace of sulfuric acid ... 

Coproductioa of ammonium sulfate is a disadvantage of the formamide route, and it has largely been supplanted by processes based on the direct hydrolysis of methyl formate. If the methanol is recycled to the carbonylation step the stoichiometry corresponds to the production of formic acid by hydration of carbon monoxide, a reaction which is too thermodynamicaHy unfavorable to be carried out directly on an iadustrial scale. 

The methanol carbonylation is performed ia the presence of a basic catalyst such as sodium methoxide and the product isolated by distillation. In one continuous commercial process (6) the methyl formate and dimethylamine react at 350 kPa (3.46 atm) and from 110 to 120°C to effect a conversion of about 90%. The reaction mixture is then fed to a reactor—stripper operating at about 275 kPa (2.7 atm), where the reaction is completed and DMF and methanol are separated from the lighter by-products. The cmde material is then purified ia a separate distillation column operating at atmospheric pressure. 

A second process is the direct carbonylation of dimethylamine [124-40-3] ia the presence of a basic catalyst or a transition metal. This carbonylation is often mn ia the presence of methanol ia order to help solubilize the catalyst (7), and presumably proceeds through methyl formate as an iatermediate. 

Ab initio molecular orbital calculations are being used to study the reactions of anionic nucleophiles with carbonyl compounds in the gas phase. A rich variety of energy surfaces is found as shown here for reactions of hydroxide ion with methyl formate and formaldehyde, chloride ion with formyl and acetyl chloride, and fluoride ion with formyl fluoride. Extension of these investigations to determine the influence of solvation on the energy profiles is also underway the statistical mechanics approach is outlined and illustrated by results from Monte Carlo simulations for the addition of hydroxide ion to formaldehyde in water. 

Yeom and Frei [96] showed that irradiation at 266 nm of TS-1 loaded with CO and CH3OH gas at 173 K gave methyl formate as the main product. The photoreaction was monitored in situ by FT-IR spectroscopy and was attributed to reduction of CO at LMCT-excited framework Ti centers (see Sect. 3.2) under concurrent oxidation of methanol. Infrared product analysis based on experiments with isotopically labeled molecules revealed that carbon monoxide is incorporated into the ester as a carbonyl moiety. The authors proposed that CO is photoreduced by transient Ti + to HCO radical in the primary redox step. This finding opens up the possibility for synthetic chemistry of carbon monoxide in transition metal materials by photoactivation of framework metal centers. 

X-ray structure analyses of Rh(COCH3)(I)2(dppp) (14) and [Rh(I I)(I)(//-I)(dppp)]2 (15), where dppp l,3-bis(diphenylphosphino) propane, were reported. Unsaturated complex (14) possesses a distorted five-coordinate geometry that is intermediate between sbp and tbp structures.69 Under CO pressure, the rhodium/ionic-iodide system catalyzes either the reductive carbonylation of methyl formate into acetaldehyde or its homologation into methyl acetate. By using labeled methyl formate (H13C02CH3) it was shown that the carbonyl group of acetaldehyde or methyl acetate does not result from that of methyl formate.70... 

When sodium ethoxide is used in place of sodium hydroxide in the carbonylation reaction of benzyl halides with dicobalt octacarbonyl, ethyl esters are produced instead of the acids [15], Esters are also produced directly from iodoalkanes through their reaction with molybdenum hexacarbonyl in the presence of tetra-/i-butylammo-nium fluoride [16]. Di-iodoalkanes produce lactones [16]. The reaction can be made catalytic in the hexacarbonyl by the addition of methyl formate [16]. t-Butyl arylacetic esters are produced in moderate yield (40-60%) under phase-transfer catalytic conditions in the palladium promoted carbonylation reaction with benzyl chlorides [17]. 

An HP IR study of the platinum catalysed carbonylation of methanol to methyl formate, revealed that the catalyst precursor, ds-[Pt(PEt3)2Cl2] is converted into cis-[Pt(PEt3)2(CO)2] along with a cluster species, [Pt3(PEt3)3(CO) ] (n = 3 or 4) [95]. A mechanism involving oxidative addition of methanol to Pt(0) followed by CO insertion into the Pt-OMe bond was suggested. 

To conclude this section on the effect of solvent on a-nucleophilicity, we refer to the current, rather controversial, situation pertaining to gas-phase smdies and the a-effect. As reported in our review on the a-effect and its modulation by solvent the gas-phase reaction of methyl formate with HOO and HO , which proceeds via three competitive pathways proton abstraction, nucleophilic addition to the carbonyl group and Sat2 displacement on the methyl group, showed no enhanced nucleophilic reactivity for HOO relative to This was consistent with gas-phase calculational work... 

The direct conversion deals with the straight hydrogenation of carbon monoxide to paraffins, olefins and heteroatom (oxygen, nitrogen) containing products. The indirect conversion invokes intermediates such as methanol, methyl formate and formaldehyde. The latter ones in a consecutive reaction can yield a variety of desired chemicals. For instance, acetic acid can be synthesized directly from CO/H2, but for reasons of selectivity the carbonylation of methanol is by far the best commercial process. 

The carbonylation-homologation reaction may also be carried out on a mixture of alcohols and their formates. For instance, at a very high conversion of the reagents, methanol-methyl formate and i-butaiol -i-butyl formate produce a mixture of oxygenates particularly rich in acetates that are useful as octane improvers for gasoline (Fig. 3). 

Figure 3. Carbonylation and homologation of methanol-methyl formate, i-butanol-i-butyl formate mixture.

Another possible reason that ethylene glycol is not produced by this system could be that the hydroxymethyl complex of (51) and (52) may undergo preferential reductive elimination to methanol, (52), rather than CO insertion, (51). However, CO insertion appears to take place in the formation of methyl formate, (53), where a similar insertion-reductive elimination branch appears to be involved. Insertion of CO should be much more favorable for the hydroxymethyl complex than for the methoxy complex (67, 83). Further, ruthenium carbonyl complexes are known to hydro-formylate olefins under conditions similar to those used in these CO hydrogenation reactions (183, 184). Based on the studies of equilibrium (46) previously described, a mononuclear catalyst and ruthenium hydride alkyl intermediate analogous to the hydroxymethyl complex of (51) seem probable. In such reactions, hydroformylation is achieved by CO insertion, and olefin hydrogenation is the result of competitive reductive elimination. The results reported for these reactions show that olefin hydroformylation predominates over hydrogenation, indicating that the CO insertion process of (51) should be quite competitive with the reductive elimination reaction of (52). 

Hydroxyacetophenone and related compounds are attractive precursors of chromanones, most notably in the synthesis of their 2-phenyl derivatives. Being adjacent to the carbonyl group, the methyl group of the acetophenone is activated and forms a carbanion on treatment with base. Subsequent condensation with a carbonyl compound which lacks an a-hydrogen atom leads to a 1,3-dicarbonyl or an enone system which readily cyclizes to a chromanone. Thus, methyl formate affords the chromanone (591) (53MI22400) and formaldehyde has been used in the synthesis of 3-methylchroman-4-one from o-hydroxypropiophenone (68T949). 

The only claim for the production of a metallocarboxylic acid from the insertion of C02 into a metal-hydrogen bond in the opposite sense is based on the reaction of C02 with [HCo(N2)(PPh3)3] (108, 136). The metallocarboxylic acid is said to be implicated since treatment of the product in benzene solution with Mel followed by methanolic BF3 yielded a considerable amount of methyl acetate as well as methyl formate derived from the cobalt formate complex. Metallocarboxylic acid species formed by attack of H20 or OH- on a coordinated carbonyl are considered in the section on CO oxidation. 

Esters behave in an analogous fashion, with carbonyl protonation being predominant [Eq. (3.66)]. Thus, protonated methyl formate 276 is present in HSC F-SbFs-S02 solution as two isomers in a ratio of 90% to 10%.571,572... 

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