Amines, metal catalyzed carbonylation

Aromatic amines have been shown to be intermediates in the metal catalyzed carbonylation of nitroaromatics to aryl carbamates. Previous research established that the novel bis(methoxycarbonyl) complex, Ru(dppe)(C0)2[C(0)0Me]2, was the most abundant species present during catalysis. In this study, the complete kinetic analysis of the reaction of p-toluidine with Ru(dppe)(C0)2[C(0)0Me]2 established that the C-N bond formed by nucleophilic attack on a metal carbonyl, and that the organic product was removed from the metal by an intramolecular elimination of aryl isocyanate. 

In the following ten chapters we wiU look at the details of the transitional metal-catalyzed carbonylative activation of C-X bonds. Depending on the nucleophiles used, their reactions mechanisms are different and have their own term as well. For example, alkoxycarbonylation refers to using alcohols as nucleophiles, aminocarbonylation means using amines as nucleophiles, and so on. Each type of reaction will be discussed separately and end with a personal prediction. 

Carbonic add diesters are very attractive reagents and of great economic interest because they represent safe, nonenvironmentally acceptable alternatives to phosgene for carbonylation and carboxylation reactions. For example, methoxycarboxylation with dimethyl carbonate offers an eco-friendly alternative route for the production of carbamates and isocyanates, which are valuable precursors of ureas (see Sections 4.3.1 and 4.3.2) [781, 782]. The method is comparable, from an environmental point of view, with the transition metal catalyzed carbonylation of nitro compounds and amines with CO. 

Raoufmoghaddam S (2014) Recent advances in catalytic C-N bond formation a comparison of cascade hydroaminomethylation and reductive amination reactions with the corresponding hydroamidomethylation and reductive amidation reactions. Org Biomol Chem 12 7179-7193 Wu X-F, Fang X, Wu L, Jackstell R, Neumann H, Beller M (2014) Transition-metal-catalyzed carbonylation reactions of olefins and alkynes a personal account. Acc Chem Res 47 1041-1053... 

There are a number of amine-catalyzed carbonylation reactions which are catalyzed by cobalt carbonyl and iron carbonyl. It seems to me that these are insertion reactions of metal amides, where carbon monoxide is inserted and then some kind of a reduction or subsequent reaction gives the observed products, urea derivatives or carbamates in alcohols. We do not know the structure of the iron compound it is probably similar to the cobalt species shown. 

Many such activated acyl derivatives have been developed, and the field has been reviewed [7-9]. The most commonly used irreversible acyl donors are various types of vinyl esters. During the acylation of the enzyme, vinyl alcohols are liberated, which rapidly tautomerize to non-nucleophilic carbonyl compounds (Scheme 4.5). The acyl-enzyme then reacts with the racemic nucleophile (e.g., an alcohol or amine). Many vinyl esters and isopropenyl acetate are commercially available, and others can be made from vinyl and isopropenyl acetate by Lewis acid- or palladium-catalyzed reactions with acids [10-12] or from transition metal-catalyzed additions to acetylenes [13-15]. If ethoxyacetylene is used in such reactions, R1 in the resulting acyl donor will be OEt (Scheme 4.5), and hence the end product from the acyl donor leaving group will be the innocuous ethyl acetate [16]. Other frequently used acylation agents that act as more or less irreversible acyl donors are the easily prepared 2,2,2-trifluoro- and 2,2,2-trichloro-ethyl esters [17-23]. Less frequently used are oxime esters and cyanomethyl ester [7]. S-ethyl thioesters such as the thiooctanoate has also been used, and here the ethanethiol formed is allowed to evaporate to displace the equilibrium [24, 25]. Some anhydrides can also serve as irreversible acyl donors. 

Another variation of the palladium-catalyzed carbonylation reaction occurs when hydrogen is added rather than an alcohol or a primary or secondary amine. This variation leads to aldehyde formation the hydrogen reduces the acylpalladium intermediate to aldehyde and metal hydride (76). A basic tertiary amine is also added as in the ester-forming reaction to neutralize the hydrogen halide formed in the dissociation of the hydride ... 

There are interesting transition metal-catalyzed-reactions that lead to aryl amides. The use of POCI3 and DMF, with a palladium catalyst, converts aryl iodides to benzamides. A palladium-catalyzed reaction of aryl hahdes and for-mamide leads to benzamide derivatives. Carbonylation is another method that generates amides. When an aryl iodide was treated with a secondary amine and Mo(CO)e, in the presence of 3 equivalents of DBU, 10% Pd(OAc)2, with micro-wave irradiation at 100°C, the corresponding benzamide was obtained. 

In 1970 the transition metal catalyzed formation of alkyl formates from CO2, H2, and alcohols was first described. Phosphine complexes of Group 8 to Group 10 transition metals and carbonyl metallates of Groups 6 and 8 show catalytic activity (TON 6-60) and in most cases a positive effect by addition of amines or other basic additives [26 a, 54-58]. A more effective catalytic system has been found when carrying out the reaction in the supercritical phase (TON 3500) [54 a]. Similarly to the synthesis of formic acid, the synthesis of methyl formate in SCCO2 is successful in the presence of methanol and ruthenium(II) catalyst systems [54 b]. 

The liquid phase NMR spectra comprise the first direct spectroscopic evidence differentiating phenoloxidase- and metal-catalyzed reactions from noncatalyzed nucleophilic addition reactions of aniline with humic substances. The solid state NMR spectra provide the first direct evidence for nucleophilic addition of aniline to quinone and other carbonyl groups in the organic matter of whole soil and peat. The NMR approach has potential for further investigation of the effects of reaction conditions on the incorporation of aromatic amines into naturally occurring organic matter, and for studies on how aromatic amines covalently bound to organic matter may ultimately be re-released or remineralized, either chemically or microbially. 

The metal-bound carbonyl ligand is readily subjected to the attack of not only carbanions but heteroatom nucleophiles such as alcohols and amines to form ligands useful for formation of compounds containing ester and amide functionalities. The ease with which the nucleophilic attack takes place at metal-coordinated alkenes and alkynes provides a basis for oxidation of these molecules in the presence of a transition metal complex catalyst [3,4a], as exemplified by the Wacker type alkene oxidation by the use of a Pd catalyst. Metal catalyzed addition of alcohols or amines to alkenes and alkynes also involve the analogous nucleophilic attack [4b-e]. The attack of carbanions and heteroatom nucleophiles... 

Metal-catalyzed reductive carbonylation of nitroaromatics using CO has been the subject of intensive investigation in recent years because of the commercial importance of amines, urethanes, and isocyanates (1). Biphasic operation could offer interesting horizons regarding the ease of catalyst recycling. Thus, palladium catalysts have been applied in the presence of water-soluble ligands such as TPPTS or BINAS (2) for the carbonylation of substituted nitroaromatics (Scheme 1). 

By 1974 the latter reaction had been generalized, and a wide variety of organic halides and other related electrophiles including alkenyl and aryl halides had been used, most notably by Heck and co-workers. Also developed in his study was a related carbonylation reaction for the synthesis of amides. Use of organometals and metal hydrides in place of alcohols and amines most notably by Steffy and Stille further expanded the scope of Pd-catalyzed carbonylation. 

Transition metal-catalyzed sp C—H amination adjacent to double bonds and carbonyl groups 12CSR931. 

The first multicomponent reaction was the Strecker reaction reported in 1850 by Adolf Strecker [241aj. It is a three-component coupling between carbonyl derivatives, amines, and cyanide source, such as hydrogen cyanide, to provide a-aminonitriles which constitute potent starting materials to achieve important a-amino acids by simple hydrolysis. The mechanism of the Strecker reaction involves the initial formation of an imine from condensation of the amine component to the carbonyl component, after which addition of the cyanide component to this imine intermediate follows. Although the first enantioselective, metal-catalyzed Strecker... 

Catalysis or Catalytic Supports, lonomers have been used as catalysts. Perfiuorosulfonated ionomers have been used as superacid catalysts in various reactions (214-216). In addition, the ionic aggregates can serve as microreactors, implying a wide range of potential applications in this area. Thus, active ions or metals in the phase-separated regions of the ionomer can be used as catalysts (206). For example, when various gases are catalyzed by cations in the multiplets, amines, hydrides, and carbonyls are formed (206,217,218). The cations in the multiplets can also be reduced, and converted to metallic particles which can also act as catalysts (219-225). 

Thirdly, ureas have been prepared by the catalyzed carbonylation of amines using carbon monoxide [738-741] or carbon dioxide [742, 743] in the presence of metal complexes, selenium [738], phosphorus compounds [744, 745], and N,N -dicyclohexylcarbodiimide [746], Moreover, the large scale production of urea derivatives by using these simpler and less expensive raw materials (CO and CO2) in catalytic processes avoids production of large amounts of saline by-products, which represent the main constituent of chemical waste. 

Grigg and co-workers have used a sequential, one-pot Petasis borono-Mannich reaction with either Pd(0)-catalyzed carbonylative amination cyclization or Pd(0)-cat-alyzed allenylation/amination cyclization (Scheme 7.7) [46]. The overall approach results in the formation of a-amino acid derivatives of isoindolone 25 and 4-methylene-3,4 -dihydroisoquinoline 26. While this is the only reported example of a combination of a Petasis borono-Mannich reaction with a Pd(0)using other Pd(0) or transition metal catalyzed reactions is a very attractive strategy for the synthesis of complex molecules or combinatorial libraries. 

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