From amines dehydrogenation

Initial imine or iminium generation from amines can be used to allow C-X (X = heteroatom) or C-C bond formation. Thus, anilines substituted in the orf/zo-position with X-H functionalities (X = 0, NMe, S) have been dehy-drogenatively condensed with benzylamines under mpg-CN photocatalysis to yield the corresponding benzofused heterocycles [122]. Via iminium intermediates, AI-aryl-l,2,3,4-tetrahydroisoquinolines could be dehydrogenatively coupled photocatalytically by mpg-CN to various carbon nucleophiles derived from nitroalkanes, malonates, and 2-alkanones, and the latter via tandem organocatalysis with proline [124]. 

Metal-catalysed amine dehydrogenation has been utilised for quinoline preparation. Shim and Cho have reported the union of 2-amino ben l alcohol with secondary alcohols in the presence of catalytic RuCl2(PPh3)3 at 80 °C to afford quinolines (Scheme 12.40). The mechanism may involve transfer of hydrogen from both alcohol reactants to dodecene (a sacrificial hydrogen acceptor) to provide the corresponding carbonyls. In the absence of dodecene, only trace product is formed evaluation of other hydrogen acceptors was not described. KOH-induced aldol condensation followed by cyclodehydration would provide the observed quinolines. 

This is an example of the Doebner synthesis of quinoline-4-carboxylic acids (cinchoninic acids) the reaction consists in the condensation of an aromatic amine with pyruvic acid and an aldehj de. The mechanism is probably similar to that given for the Doebner-Miller sj nthesis of quinaldiiie (Section V,2), involving the intermediate formation of a dihydroquinoline derivative, which is subsequently dehydrogenated by the Schiff s base derived from the aromatic amine and aldehyde. 

The 1,4-isomer has been similarly generated from terephthalonitdle [623-26-7] (56) using a mixed Pd/Ru catalyst and ammonia plus solvent at 125 °C and 10 MPa (100 atm). It is also potentially derived (57) from terephthaUc acid [100-21-0] by amination of 1,4-cyclohexanedimethanol (30) [105-08-8], Endocyclization, however, competes favorably and results in formation of the secondary amine (31) 3-a2abicyclo[3.2.2]nonane [283-24-9] upon diol reaction with ammonia over dehydration and dehydrogenation catalysts (58) ... 

A variant on this structure, dioxyline, has much the same activity as the natural product but shows a better therapeutic ratio. Reduction of the oxime (113) from 3,4-dimethoxyphenyl-acetone (112) affords the veratrylamine homolog bearing a methyl group on the amine carbon atom (114). Acylation of this with 4-ethoxy-3-methoxyphenyl acetyl chloride gives the corresponding amide (115). Cyclization by means of phosphorus oxychloride followed by dehydrogenation over palladium yields dioxyline (116). ... 

Purely parallel reactions are e.g. competitive reactions which are frequently carried out purposefully, with the aim of estimating relative reactivities of reactants these will be discussed elsewhere (Section IV.E). Several kinetic studies have been made of noncompetitive parallel reactions. The examples may be parallel formation of benzene and methylcyclo-pentane by simultaneous dehydrogenation and isomerization of cyclohexane on rhenium-paladium or on platinum catalysts on suitable supports (88, 89), parallel formation of mesityl oxide, acetone, and phorone from diacetone alcohol on an acidic ion exchanger (41), disproportionation of amines on alumina, accompanied by olefin-forming elimination (20), dehydrogenation of butane coupled with hydrogenation of ethylene or propylene on a chromia-alumina catalyst (24), or parallel formation of ethyl-, methylethyl-, and vinylethylbenzene from diethylbenzene on faujasite (89a). 

It was thought that propionitrile came from dehydrogenation of the anti-Markovnikov hydroamination product, w-PrNHj. Propionitrile can break down to ethylene and HCN, the former reacting with NH3 to generate acetonitrile via ethyl-amine, the latter adding to propene to form the butyronitriles [26, 37]. 

Aryl alcohol oxidase from the ligninolytic fungus Pleurotus eryngii had a strong preference for benzylic and allylic alcohols, showing activity on phenyl-substituted benzyl, cinnamyl, naphthyl and 2,4-hexadien-l-ol [103,104]. Another aryl alcohol oxidase, vanillyl alcohol oxidase (VAO) from the ascomycete Penicillium simplicissimum catalyzed the oxidation of vanillyl alcohol and the demethylation of 4-(methoxymethyl)phenol to vanillin and 4-hydro-xybenzaldehyde. In addition, VAO also catalyzed deamination of vanillyl amine to vanillin, and hydroxylation and dehydrogenation of 4-alkylphenols. For the oxidation of 4-alkylphenol, the ratio between the alcohol and alkene product depended on the length and bulkiness of the alkyl side-chain [105,106]. 4-Ethylphenol and 4-propylphenol, were mainly converted to (R)-l-(4 -hydroxyphenyl) alcohols, whereas medium-chain 4-alkylphenols such as 4-butylphenol were converted to l-(4 -hydroxyphenyl)alkenes. 

Consequently, by choosing proper conditions, especially the ratios of the carbonyl compound to the amino compound, very good yields of the desired amines can be obtained [322, 953]. In catalytic hydrogenations alkylation of amines was also achieved by alcohols under the conditions when they may be dehydrogenated to the carbonyl compounds [803]. The reaction of aldehydes and ketones with ammonia and amines in the presence of hydrogen is carried out on catalysts platinum oxide [957], nickel [803, 958] or Raney nickel [956, 959,960]. Yields range from low (23-35%) to very high (93%). An alternative route is the use of complex borohydrides sodium borohydride [954], lithium cyanoborohydride [955] and sodium cyanoborohydride [103] in aqueous-alcoholic solutions of pH 5-8. 

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