Acetic amidocarbonylation

Amidocarbonylation of allyl acetate, 2-pentenenitrile and allyl alcohol eth-oxylates realizes the corresponding amido acids in good yields (Table 2). Potential applications for these products also include surfactants and polyamide-polyesters. 

Other amido acids may be prepared via formaldehyde amidocarbonylation using dicobalt octacarbonyl in the presence of A -substituted acyclic amides or cyclic amides. Amidocarbonylation of 2-pyrrolidone and -caprolactam [22] affords N-(2-pyrrolidone)-2-acetic acid and A-(e-caprolactam)-2-acetic acid, respectively (eqs. (12) and (13)). The side products shown can be recycled and eventually converted to the desired amido acetic acids. 

The N-acetyl-D,L-amino acid precursors are conveniently accessible through either acetylation of D,L-amino acids with acetyl chloride or acetic anhydride in a Schotten-Baumann reaction or via amidocarbonylation I801. For the acylase reaction, Co2+ as metal effector is added to yield an increased operational stability of the enzyme. The unconverted acetyl-D-methionine is racemized by acetic anhydride in alkali, and the racemic acetyl-D,L-methionine is reused. The racemization can also be carried out in a molten bath or by an acetyl amino acid racemase. Product recovery of L-methionine is achieved by crystallization, because L-methionine is much less soluble than the acetyl substrate. The production is carried out in a continuously operated stirred tank reactor. A polyamide ultrafiltration membrane with a cutoff of 10 kDa retains the enzyme, thus decoupling the residence times of catalyst and reactants. L-methionine is produced with an ee > 99.5 % and a yield of 80% with a capacity of > 3001 a-1. At Degussa, several proteinogenic and non-proteinogenic amino acids are produced in the same way e.g. L-alanine, L-phenylalanine, a-amino butyric acid, L-valine, l-norvaline and L-homophenylalanine. 

Various unsaturated compounds can be inserted into the metal alkyl, aryl, and alkenyl complexes to give new organometallic complexes having various functional groups. The insertions of carbon monoxide (CO) and isocyanide (CNR) into transition metal-carbon a-bond are particularly important processes, since a carbon unit can be increased in the process and the acyl type complexes formed by the insertion processes can be subjected to further transformations to synthesize useful organic compounds. For example, the CO inserhon constitutes a fundamental step in industrially important processes such as hydroformylation of olefins, acetic acid synthesis from methanol and CO, Fischer-Tropsch process, amidocarbonylation, olefin and CO copolymerizahon processes as well as in a variety of laboratory syntheses of carbonyl containing compounds. 

A broad range of olefins, acetals, epoxides, alcohols, and chlorides were demonstrated effective alternative starting materials. Cobalt and rhodium carbonyls and bimetallic complexes catalyzed the domino hydroformylation-amidocarbonylation of olefins (17-22). Addition of 0.1 mol% RheCCOie to the cobalt catalyst gave branched AT-acetyltrifluorovaline, which indicated that the hydroformylation step governs the regioselectivity of the domino process (Scheme 4) (22). 

Carbonylation Reactions. A three-component palladium-catalyzed amidocarbonylation reaction provides IV-acylamino acids from aromatic and aliphatic aldehydes or acetals with amides under elevated CO pressure (60 bar) in the presence of PdBr2, PPhs, LiBr, an acid additive (typically H2SO4), and iV-methyl-2-pyrrolidone. Mechanistically, the palladium-catalyzed amidocarbonylation reaction is proposed to proceed through the in situ formation of an a-haloamide and Pd(0) species, which can undergo oxidative addition, followed by CO insertion, and lastly hydrolysis of the acyl palladium complex to afford the product and regenerate the catalyst (eq 45). 

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