Homologation of methanol

The formation of the a-methyl derivative is extremely surprising. We can propose a reasonable mechanism based on Wender s proposed mechanism for cobalt catalyzed CO homologation of methanol (5). 

Ethanol production by homologation of methanol can be achieved by hydrogenation of C02 (Eq. (20)) [116], Sasaki s group showed that both Ru and Co car-... 

Iron-catalyzed carbonylations, 34 124-125 Fe(CO)5/amine catalysts, 34 124 homologation of methanol, 34 124 proposed mechanism for, 34 125 Iron complexes... 

The main emphasis has been on the homologation of methanol to ethanol (O. Homologation of substrates other than methanol has up till now been less widely studied. However, there is an increasing interest in the hydrocarbonylation of esters, as is evidenced by e.g. the development of the Halcon process (2 ) for the production of ethyli-dene diacetate as a precursor for vinyl acetate. 

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

In the future, there is no doubt that alcohols will play a major role not only as fuel components (70,71) but also as feed stocks for the syntheses of more complicated organic compounds (72). A great amount of research effort is presently directed to the economic conversion of CO and to methanol (73), and on homologation of methanol to higher alcohols (74). Conversion of synthesis gas from coal to acetic anhydride (75) through the intermediacy of methyl acetate (from methanol) will soon be a commercial reality. 

Representative Product Distributions for the Homologation of Methanol Using Cobalt in Both Batchwise and Continuous Mode Experiments"... 

Carbonylation and Homologation of Dimethyl Ether and Homologation of Methanol and Methyl... 

Workers at Argonne Laboratory have recently discovered a catalytic method for the homologation of methanol to ethanol 122-124). The workers consider the mechanism to involve initial formation of acetaldehyde, followed by its hydrogenation. 

The Shell process uses a cobalt/phospfaine catalyst for the homologation of methanol CH3-OH +CO + 2Ha CH3CH2OH H2O... 

Homologation of methanol represents another promising way into ethanol and other C3 chemicals. 

The homologation of methanol has been proved to be a most promising process for the production of oxygenated Cj chemicals. A survey of the recent literature demonstrates the considerable efforts to improve yields and selectivilies of this synthesis gas reaction. The complex influence of catalyst composition and reaction conditions has been empltasizcd, and although the course of the reaction is not fully understood, recent results suggest a mechanistic pattern similar to that of methanol carbonylation. 

G Braca, C. Sbrana, G. Valentmi, C- Andrich and G. Gregorio Carbonytation and Homologation of Methanol, Methyl Ethers and Esters in the presence of Ruthenium Catalysis (Fundamental Research in Homogeneous Catalysis v. 3. ed.. M. Tsutsui), pp. 221 238. Plenum Prevs (1979). 

Co3RuH(CO)i2 and/or salt of [Co3Ru(CO)i2] were reported to act as homogeneous catalysts in the homologation of methanol. Co3RuH(CO)i2 has been also applied to yield, by controlled thermal decomposition, very active heterogeneous Fischer-Tropsch catalysts. ... 

Homologation of methanol to the acetyl-moiety. CH3OH + HI ->CHal +H2O... 

The ruthenium-cobalt bimetallic complex system catalyzes the homologation of methanol with carbon dioxide and hydrogen in the presence of iodide salts. A synergistic effect is found between these two metals. The yield of ethanol is also affected by the Lewis acidity of the iodide salt, lithium iodide being most effective. The reaction profile shows that methanol is homologated with CO formed by the hydrogenation of CO2. 

Table 1. Homologation of methanol - current state in the development of catalysts. 

As proposed by Keister [57] and supported by own investigations [58], phosphines are partly quartemized, so in the reaction mixture from the homologation of methanol in the presence of triphenylphosphine and hydroiodic acid methyltri-phenylphosphonium iodide could be isolated and identified by IR spectroscopy, which shows a quantitative methylation of the intermediate formed [HPPhs] " with methanol. This fact suggests a phosphonium ion mechanism, which is proposed by the author and outlined in Scheme 3. 

Scheme 3. Phosphonium ions as methyl-group transfer agents in the homologation of methanol.

The elongation of the carbon chain of these molecules by a CH2 unit derived from CO/H2 is called homologation. Without any doubt, the syngas homologation of methanol to ethanol, once achieved on an industrial scale, would have enormous commercial potential, since it represents the key step in a syngas route to ethylene (249). 

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