The Gattermann-Koch Reaction

In addition, high ortho regioselectivity (32%) was observed for bibenzyl, whereas biphenyl, diphenylmethane and 1,3-diphenylpropane exhibited the usual high para regioselectivity (100%, 98%, and 95%, respectively).95 

In these cases the formation of a n complex was suggested to occur from the protonated aromatic (a complex) and the proelectrophile (P) followed by the formation of the a complex as suggested by Cacace 96 

A similar initial interaction between the arene and the Lewis acid catalyst was suggested recently on the basis of theoretical calculations.97 

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The Gattermann-Koch reaction when appHed to alkenes or alkanes gives ketones or acids but not aldehydes. However, the Vilsmeier aldehyde synthesis can be appHed to aUphatic compounds. For example, 1,2-diaLkoxyethylenes react with /V-methy1foTmani1ide and POCl to give alkoxymalondialdehydes ... 

When aqueous solutions of aromatic and heteroaromatic diazonium salts are treated with cuprous chloride, -bromide, or -cyanide, the corresponding aromatic chlorides, bromides, or cyanides are formed, respectively. In many cases the anions mentioned must be present in excess. This reaction, the Sandmeyer reaction, was discovered by Sandmeyer in 1884. A variant carried out with copper powder and HBr or HC1 was for many years called the Gattermann reaction (Gattermann, 1890). As it is often confused with the Gattermann-Koch reaction (ArH + CO + HC1 ArCHO), and as it is mechanistically not significantly different from Sandmeyer s procedure, the name Gattermann reaction should be avoided. 

Formylation may be carried out by use of CO, HC1, and A1C13 (the Gattermann-Koch reaction) it is doubtful whether HCOC1 is... 

When rearrangements occur in these systems, the products obtained will often be thermodynamically rather than kinetically determined (62). In some instances—e.g., the Gattermann-Koch reaction—the stability of the complex produced is responsible for the fact that the reaction can be carried out at all (4, 9). 

The Gattermann synthesis is somewhat less selective than the Gattermann-Koch reaction. In the HCN—HC1—A1C13 system, the substrate selectivity is 49.1, with 56.4% of para-isomer formation, whereas the corresponding values for the Zn(CN)2—HC1—A1C13 system in nitromethane solvent are 128 and 63.9%, respectively.90... 

Crafts alkylation and acylation (Section 22-4E and 22-4F), the Gattermann-Koch reaction for preparation of aldehydes from arenes and carbon monoxide (Section 22-4F), and the Kolbe-Schmitt, Reimer-Tiemann, and Gattermann reactions for synthesis of acids and aldehydes from arenols (Section 26-1E). 

Among the most frequently used formylation methods, the Gattermann-Koch reaction shows the highest selectivity reflected both in the observed high toluene- benzene rate ratios as well as a high degree of para substitution (Table 5.30). 

The Gattermann-Koch reaction, in which carbon monoxide and hydrogen chloride are bubbled through a solution containing benzene and aluminium chloride, is a further example of direct formylation (Scheme 6.5). The formyl cation, HC=0, is thought to be the attacking electrophile, though it is probably complexed to Al. 

O. R. XVIII-I, M. J. Jorgenson, Preparation of Ketones from the Reaction of Organo-lithium Reagents with Carboxylic Acids XVI, A. J. Nielsen and W. J. Houlihan, The Aldol Condensation IV-5, W. S. Ide and J. S. Buck, The Synthesis of Benzoins II-3, T. A. Geissman, The Cannizzaro Reaction V-6, N. N. Crounse, The Gattermann-Koch Reaction I-10, F. f. 3licke, The Mannich Reaction. ... 

Dilke, M. H., Eley, D. D. The Gattermann-Koch reaction. II. Reaction kinetics. J. Chem. Soc., Abstracts 1949, 2613-2620. 

The Gattermann-Koch reaction (which uses CO, HC1 and A1C13) can be used to produce an aromatic aldehyde, rather than a ketone. 

A variant of the Gattermann-Koch reaction due to Rieche, Gross, and Hoft594 and applicable to aromatic hydrocarbons, phenols and their ethers, and heterocyclic compounds consists of the reaction of these compounds with alkyl dichloromethyl ethers in the presence of tin tetrachloride or aluminum... 

The Gattermann-Koch reaction provides one such formylation method. In this reaction, benzene (or an alkylbenzene) is treated with carbon monoxide (CO), HCl, and AICI3. The CO and HCl combine to produce formyl chloride in situ. The usual reaction of the acid chloride with AICI3 enables the Friedel-Crafts acylation to proceed, affording benzaldehyde. 

Thermodynamics can also be usefully employed in analyzing the role of the catalyst. A typical example, illustrated below, is the Gattermann-Koch reaction ... 

The simplest acyl chloride, formyl chloride, H-C-Cl, is unstable, decomposing to HCl and CO upon attempted preparation. ThCTefore, direct Friedel-Crafts formylation of benzene is impossible. An alternative process, the Gattermann-Koch reaction, enables the introduction of the formyl group, -CHO, into the benzene ring by treatment with CO under pressure, in the presence of HCl and Lewis acid catalysts. For example, methylbenzene (toluene) can be formylated at the para position in this way in 51% yield. The electrophile in this process was observed directly for the first time in 1997 by treating CO with HF-SbFs under high pressure C NMR 8 139.5 ppm IR V = 2110 cm . What is the structure of this species and the mechanism of its reaction with methylbenzene Explain the spectral data. (Hints Draw the Lewis structure of CO and proceed by considering the species that may arise in the presence of acid. The comparative spectral data for free CO are C NMR 8 = 181.3 ppm IR P = 2143 cm . )... 

The Gattermann-Koch reaction can be carried out under two major types of conditions i.e. at atmospheric pressure where CU2CI2 is necessary as a promoter or complexing agent and secondly at high-pressure where the presence of CU2CI2 is not necessary. The Gattermann-Koch aldehyde synthesis is a suitable method for the preparation of simple aromatic aldehydes such as benzaldehyde and tolualdehyde. Formylation of ortho and... 

As the Gattermann-Koch reaction fails to produce aldehydes from phenol and phenolic ethers, Gattermann and co-workers " developed an alternative method that produces aldehydes from phenols, phenol ethers and heterocyclic compounds successfully. The method involves the addition of HCN and HCI to the aromatic substrate, with or without the presence of an acidic halide catalyst (Eq 1.17)... 

A simpler way to accomplish this transformation involves the Gattermann-Koch reaction (Figure 13.46) we may consider this as a way to produce [HC(=0)] in situ. 

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