Formates/formic acid synthesis

The turnover frequency (TOF = mole of product per mole of catalyst per hour) of this rapid reaction is rather high, with values up to 1400. This reaction, carried out at 50 °C in SC-CO2, is 18 times faster than in conventional tetrahydrofuran under otherwise identical reaction conditions. This formic acid synthesis can be coupled with subsequent reactions by addition of methanol or dimethylamine, this supercritical reaction system provides a highly efficient one-pot route to methyl formate and A,A-dimethylforma-mide, respectively [918]. Another example of a reaction in which carbon dioxide acts as both reactant and reaction medium is the formation of tetraethyl-2-pyranone from hex-3-yne and CO2 in the presence of an Ni(II)-diphosphane catalyst at 102 °C under supercritical reaction conditions [919]. 

Furthermore, methanol is the raw material for formic acid synthesis by the carbonylation route, leading to methyl formate (HCOOCH3), which is hydrolyzed while formic acid is separated by a combination of extraction and distillation steps... 

Addition of a hydroxy group to alkynes to form enol ethers is possible with Pd(II). Enol ether formation and its hydrolysis mean the hydration of alkynes to ketones. The 5-hydroxyalkyne 249 was converted into the cyclic enol ether 250[124], Stereoselective enol ether formation was applied to the synthesis of prostacyclin[131]. Treatment of the 4-alkynol 251 with a stoichiometric amount of PdCl2, followed by hydrogenolysis with formic acid, gives the cyclic enol ether 253. Alkoxypalladation to give 252 is trans addition, because the Z E ratio of the alkene 253 was 33 1. 

Formic acid is used as an intermediate in the production of a number of dmgs, dyes, flavors, and perfume components. It is used, for example, in the synthesis of aspartame and in the manufacture of formate esters for flavor and fragrance appHcations. 

There are several schemes for the synthesis of cellulose formates (slow) reaction of the polymer with formic acid faster reaction in the presence of a mineral acid catalyst, e.g., sulfuric or phosphoric acid. The latter route is usually associated with extensive degradation of the polymer chain. Reaction of SOCI2 with DMF produces the Vilsmeier-Haack adduct (HC(Cl) = N (CH3)2C1 ) [145]. In the presence of base, cellulose reacts with this adduct to form the unstable intermediate (Cell - O - CH = N" (CH3)2C1 ) from which cellulose formate is obtained by hydrolysis. The DS ranges from 1.2 to 2.5 and the order of reactivity is 5 > C2 > C3 [140-143,146]. 

This is illustrated by the TPD spectra of formate adsorbed on Cu(lOO). To prove that formate is a reaction intermediate in the synthesis of methanol from CO2 and H2, a Cu(lOO) surface was subjected to methanol synthesis conditions and the TPD spectra recorded (lower traces of Fig. 7.13). For comparison, the upper traces represent the decomposition of formate obtained by dosing formic acid on the surface. As both CO2 and H2 desorb at significantly lower temperatures than those of the peaks in Fig. 7.13, the measurements represent decomposition-limited desorptions. Hence, the fact that both decomposition profiles are identical is strong evidence that formate is present under methanol synthesis conditions. 

The synthesis of cellulose by A. xylinum from various polyalcohols14 is accompanied by the formation of carbon dioxide, formic acid, nonvolatile acids, ketoses and sometimes ethanol. The much greater variety of substrates suitable for cellulose synthesis, as compared with the small number for dextran or levan, may account for the widespread natural occurrence of cellulose. 

However, since the goal of this work was the synthesis of alcohols from olefins via hydrohydroxymethylation (75, 76), little attention was given to developing a shift-catalyst per se. Pettit has recently reexamined some of this work and shown that, by careful control of the pH of the reaction mixture, systems based on either Fe(CO)5 or Cr(CO)6 can be developed for the production of either formic acid or methanol from carbon monoxide and water (77, 78). Each of these latter systems involves the formation of metal hydride complexes consequently, molecular hydrogen is also produced according to the shift reaction [Eq. (16)]. 

The intermolecular reaction of phenols with propiolic esters occurs in the presence of a Pd(OAc)2 catalyst to afford coumarin derivatives directly.48,48a An exclusive formation of 5,6,7-trimethoxy-4-phenylcoumarin is observed in the Pd(OAc)2-catalyzed reaction of 3,4,5-trimethoxyphenol with ethyl phenylpropiolate in TFA (Equation (46)). Coumarin derivatives are obtained in high yields in the cases of electron-rich phenols, such as 3,4-methylenedioxyphenol, 3-methoxyphenol, 2-naphthol, and 3,5-dimethylphenol. A similar direct route to coumarin derivatives is accomplished by the reaction of phenols with propiolic acids (Equation (47)).49 A similar reaction proceeds in formic acid at room temperature for the synthesis of coumarins.50,50a Interestingly, Pd(0), rather than Pd(n), is involved in this reaction. 

Other mechanisms for the synthesis of alkylformates, not via formic acid esterification, are possible. Hydrogenation of C02 to CO, followed by catalytic car-bonylation of alcohol, would produce alkyl formate. This mechanism seems more likely for the anionic metal carbonyls because they are known catalysts for alcohol carbonylation. However, Darensbourg and colleagues [64, 74, 85] showed... 

Preparation of formamides from COz and a non-tertiary amine by homogeneous hydrogenation has been well studied and is extremely efficient (Eq. (12)). Essentially complete conversions and complete selectivity can be obtained (Table 17.3). This process seems more likely to be industrialized than the syntheses of formic acid or formate esters by C02 hydrogenation. The selectivity is excellent, in contrast to the case for alkyl formates, because the amine base which would stabilize the formic acid is used up in the synthesis of the formamide consequently little or no formic acid contaminates the product. The only byproducts that are likely to crop up in industrial application are the methylamines by overreduction of the formamide. This has been observed [96], but not with such high conversion that it could constitute a synthetic route to methylamines. 

Olah and co-workers reported the synthesis of 2,2,5,5-tetranitronorbornane (127) from 2,5-norbornadiene (122). In this synthesis formylation of (122) with formic acid yields the diformate ester (123), which on treatment with chrominm trioxide in acetone yields 2,5-norbomadione (124). Formation of the dioxime (125) from 2,5-norbornadione (124) is followed by direct oxidation to 2,5-dinitronorbomane (126) with peroxytriflnoroacetic acid generated in situ from the reaction of 90 % hydrogen peroxide with TFAA. Oxidative nitration of 2,5-dinitronorbornane (126) with sodium nitrite and potassium ferricyanide in alkaline solution generates 2,2,5,5-tetranitronorbornane (127) in excellent yield. 

In 1976 he was appointed to Associate Professor for Technical Chemistry at the University Hannover. His research group experimentally investigated the interrelation of adsorption, transfer processes and chemical reaction in bubble columns by means of various model reactions a) the formation of tertiary-butanol from isobutene in the presence of sulphuric acid as a catalyst b) the absorption and interphase mass transfer of CO2 in the presence and absence of the enzyme carboanhydrase c) chlorination of toluene d) Fischer-Tropsch synthesis. Based on these data, the processes were mathematically modelled Fluid dynamic properties in Fischer-Tropsch Slurry Reactors were evaluated and mass transfer limitation of the process was proved. In addition, the solubiHties of oxygen and CO2 in various aqueous solutions and those of chlorine in benzene and toluene were determined. Within the framework of development of a process for reconditioning of nuclear fuel wastes the kinetics of the denitration of efQuents with formic acid was investigated. 

---