Acetyl cobalt

An acetyl cobalt intermediate 1 then formed by CO insertion (or methyl miration). which is subsequently hydrogenated to give ethanol and HCo(CO)4 (cf. Equations (13). (14)) (4]. 

Next, the migratory CO insertion, which is considered as the rate-determining step (rds), followed by coordination of a CO ligand gives the acetyl-cobalt complex [Co(COCH3)(CO)4] (Eq. 20.5) [5, 6]. 

The higher iodides, however, tend to be unstable and decomposition occurs to the lower iodide (PI5 -> PI3). Anhydrous chlorides and bromides of some metals may also be prepared by the action of acetyl (ethanoyl) halide on the hydrated ethanoate (acetate) in benzene, for example cobalt(II) and nickel(II) chlorides ... 

With weak catalysts such as aluminium alkoxides with C0C13, cobalt acetyl acetonate, etc. polymerization was exceedingly slow. 

The most important physiological role of CODH in the metabolism of acetogenic bacteria was unknown until 1985, when it was shown that the enzyme is bifunctional and has acetyl-CoA synthase activity (121). It was previously thought that acetyl-CoA was synthesized at the cobalt center of a vitamin-Bi2-containing protein. In the same paper, it was proposed that nickel is the active site of CO oxidation and acetyl-CoA synthesis. 

The amidocarbonylation of aldehydes provides highly efficient access to N-acyl a-amino acid derivatives by the reaction of the ubiquitous and cheap starting materials aldehyde, amide, and carbon monoxide under transition metal-catalysis [1,2]. Wakamatsu serendipitously discovered this reaction when observing the formation of amino acid derivatives as by-products in the cobalt-catalyzed oxo reaction of acrylonitrile [3-5]. The reaction was further elaborated to an efficient cobalt- or palladium-catalyzed one-step synthesis of racemic N-acyl a-amino acids [6-8] (Scheme 1). Besides the range of direct applications, such as pharmaceuticals and detergents, racemic N-acetyl a-amino acids are important intermediates in the synthesis of enantiomeri-cally pure a-amino acids via enzymatic hydrolysis [9]. 

A cobalt catalysed carbonylation reaction converts A-substituted 1-aza-1,3-dienes into A-allylacetamides by a reductive acylation process [31]. Acetamides are byproducts of the reaction. In contrast, Schiff bases undergo a double A,C-acetylation under the same conditions producing a-acetamido ketones and A,A-disubstituted acetamides [32],... 

Acetylation occurs at the 2-position of allene systems (Scheme 8.14). The intermediate 7t-allyl complex breaks down via the nucleophilic displacement of the cobalt carbonyl group by the hydroxide ion to produce the hydroxyketone (7) [ 11 ]. An alternative oxygen-initiated radical decomposition of the complex cannot, however, be totally precluded. The formation of a second major product, the divinyl ketone (8), probably arises from direct interaction of the dicobalt octacarbonyl with the allene and does not require the basic conditions. 

Oxidation of HMF was also attempted in situ directly from fructose, using a membrane reactor or encapsulating PtBi/C into a polymeric silicone matrix, and again, with air as the oxidant. However, the yield was never more than 25%. A further attempt to obtain FDCA directly from fructose involved a one pot reaction in the presence of cobalt acetyl-acetonate encapsulated in sol-gel silica, at 155 °C and with 2 MPa of air pressure giving FDCA with 99% selectivity directly from fructose at a conversion of 72%. ... 

Some 2,3-unsaturated sugars have also been prepared by the reaction of 2-iodinated carbohydrates with sodium cobalt tetra-carbonyl and carbon monoxide.188 Methyl 3,4,6-tri-0-acetyl-2-deoxy-2-iodo-/3-D-glucopyranoside (149) in ether reacts at room temperature to give, in high yield, methyl 4,6-di-0-acetyl-2,3-dideoxy-/3-D-eri/thro-hex-2-enopyranoside (150). Under the same reaction conditions,... 

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