Catalytic reactions involving amines

Strictly related to catalytic reactions involving CO and H20 are reactions in which CO and alcohols, ROH, or CO and amines, R2NH, are used as building blocks. The catalytic addition of carbon monoxide and an alcohol to an olefin yields carboxylic esters (hydroesterification). Thus, the synthesis of methyl propionate from ethylene, CO, and methanol using a catalytic system composed of Ru3(CO)u and [PPh4]I (190°C, 20 bar C2H4, 45 bar CO, 2.5 hr, yield 74%, CT 1000) has been reported (323) ... 

Experience in air separation plant operations and other ciyogenic processing plants has shown that local freeze-out of impurities such as carbon dioxide can occur at concentrations well below the solubihty limit. For this reason, the carbon dioxide content of the feed gas sub-jec t to the minimum operating temperature is usually kept below 50 ppm. The amine process and the molecular sieve adsorption process are the most widely used methods for carbon dioxide removal. The amine process involves adsorption of the impurity by a lean aqueous organic amine solution. With sufficient amine recirculation rate, the carbon dioxide in the treated gas can be reduced to less than 25 ppm. Oxygen is removed by a catalytic reaction with hydrogen to form water. 

Several studies were performed in order to establish the mechaiusm (5-7). The currently accepted mechartism, presented in Scheme 26.1 for the Pd(BINAP) catalyzed amination, involves the formation of a complex, Pd(BINAP)2 from a catalyst precursor (usually Pd(OAc)2 or Pd2(dba)3) and ligand this complex lies outside the catalytic cycle and undertakes dissociation of one BINAP to form Pd(BINAP) the following steps are the oxidative addition of the aryl halide to the Pd(BINAP), reaction with amine and base, and the reductive elimination of the product to reform Pd(BlNAP). 

In addition to bromides and iodides, the reaction has been successfully extended to chlorides,163 triflates,164 and nonafluorobutanesulfonates (nonaflates).165 These reaction conditions permit substitution in both electron-poor and electron-rich aryl systems by a variety of nitrogen nucleophiles, including alkyl or aryl amines and heterocycles. These reactions proceed via a catalytic cycle involving Pd(0) and Pd(II) intermediates. 

Surface Chemical Analysis. Electron spectroscopy of chemical analysis (ESCA) has been the most useful technique for the identification of chemical compounds present on the surface of a composite sample of atmospheric particles. The most prominent examples Include the determination of the surface chemical states of S and N in aerosols, and the investigation of the catalytic role of soot in heterogeneous reactions involving gaseous SO2, NO, or NH3 (15, 39-41). It is apparent from these and other studies that most aerosol sulfur is in the form of sulfate, while most nitrogen is present as the ammonium ion. A substantial quantity of amine nitrogen also has been observed using ESCA (15, 39, 41). 

A significant part of the examples of transition metal catalyzed formation of five membered heterocycles utilizes a carbon-heteroatom bond forming reaction as the concluding step. The palladium or copper promoted addition of amines or alcohols onto unsaturated bonds (acetylene, olefin, allene or allyl moieties) is a prime example. This chapter summarises all those catalytic transformations, where the five membered ring is formed in the intramolecular connection of a carbon atom and a heteroatom, except for annulation reactions, involving the formation of a carbon-heteroatom bond, which are discussed in Chapter 3.4. 

Schechter 55) proposed that the catalytic effect of hydroxyl groups on the epoxide-amine addition reaction involved a termolecular activated complex formed in the concerted reaction of amine, epoxide and hydroxyl. Smith 57) suggested a modified mechanism in which the same activated complex is formed in a bimolecular reaction between an adduct formed from epoxide (E) and the proton donor (HX), and the amine ... 

In Section 6.3.6, it was emphasized that C02 and secondary amines could add to terminal alkynes in the presence of ruthenium catalysts to afford carbamates. Under comparable conditions (393-413 K, 5 MPa Ru-catalysts), primary amines will afford symmetrical disubstituted ureas in moderate yield [131]. It is worth noting that although the final urea does not contain the starting alkyne, its catalytic formation requires, besides the Ru-catalyst, the presence of a stoichiometric amount of a 1-alkyne (e.g., a propargylic alcohol). A possible mechanism (Scheme 6.32) for this catalytic reaction may involve activation of the alkyne at the metal center, a nucleophilic addition of the carbamate to the activated alkyne to produce... 

The preparation of optically active /Mactams by asymmetric synthesis is also a topic of major interest, because of the pharmaceutical and biochemical importance of those molecules [44]. A typical and economical route consists of a [2+2]-cycloaddition of a ketene to an imine. Many diastereoselective versions of this reaction type are known [45] as well as catalytic processes involving chiral (metal) catalysts [46, 47] or biocatalysts [48]. A [2+2]-cycloaddition of a ketene to an imine, however, can also be performed very efficiently when applying nucleophilic amines as chiral catalysts [49-60]. Planar-chiral DMAP derivatives have also been found to be suitable catalysts [61]. 

This atom economic reaction, in which only water occurs as a by-product, is very attractive for forming various amines. Hydroaminomethylation includes three different mechanisms due to the three reactions involved. The mechanism of hydroaminomethylation is shown in Scheme 17. The first catalytic cycle is similar to hydroformylation, which is described above. 

The formation of alkoxo intermediates may be occurring when monophosphines are used, but the stability of the amine complexes favors the deprotonation of coordinated amine. Instead, the alkoxo complexes may be important in catalytic systems involving chelating ligands [51]. Indeed, the DPPF complex [Pd(DPPF)(p-Bu C6H4)(0-f-Bu) reacted with diphenyl amine, aniline, or piperidine, as shown in Eq. (48), to give the product of amine arylation in high yields in each case [51]. Since, no alkali metal is present in this stoichiometric reaction, the palladium amide is formed by a mechanism that cannot involve external deprotonation by alkali metal base. 

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