Amines dehydrogenative carbonylation

The reaction, which is the dehydrogenative carbonylation of amines, involves carbamoyl derivatives as reactive intermediates . 

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. 

Nitrones have been generally prepared by the condensation of /V-hydroxylamines with carbonyl compounds (Eq. 8.40).63 There are a number of published procedures, including dehydrogenation of /V,/V-disubstituted hydroxylamines, / -alkylation of imines, and oxidation of secondary amines. Among them, the simplest method is the oxidation of secondary amines with H202 in the presence of catalytic amounts of Na2W04 this method is very useful for the preparation of cyclic nitrones (Eq. 8.41).64... 

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. 

Table 1 shows that methyl dodecanoate is easily converted into amine in the presence of CuCr deposited on alumina or on titania. Nevertheless one can observe that the methylation reaction is rather difficult and favoured by alumina. Moreover, a significant increase of N-dimethyl dodecylamine is obtained when the reaction is carried out with a large excess of hydrogen. Due to the mechanism of the reaction this is unexpected indeed it is generally considered that the methylation of primary amine with methanol requires i) the dehydrogenation of alcohol into a carbonyl compound and ii) a further reaction of this compound with primary amine or secondary amine via imine or enamine intermediates. 

L=CO, cycloolefins, maleic anhydride, isocyanides, amines, phosphines, sulfoxides, etc.). In most cases loss of the two carbonyl groups occurs in a single step. The ion C5H5MJ1C5H8 from the cyclopentene derivative undergoes dehydrogenation to give the ion... 

Schwoegler and Adkins (93) reacted alcohols with primary and secondary amines over Raney nickel to form secondary and tertiary amines, respectively. Since tertiary alcohols do not undergo the reaction, it is assumed that the catalyst dehydrogenates the alcohol to a carbonyl compound which reacts with an amine to give a product that can be readily hydrogenated to a more complex amine. Piperidine was reacted with ethyl, n-butyl, and n-dodecyl alcohols to give 82, 70, and 69% yields, respectively, of the corresponding alkylpiperidines. 

Enaminones. Tertiary amines substituted by a carbonyl group at the P-position undergo dehydrogenation to enaminones when treated with the Pd(ll) complex (1 equiv.) and triethylamine (2 equiv.) in acetonitrile (equation 1). 

The spectrum of applications of potassium permanganate is very broad. This reagent is used for dehydrogenative coupling [570], hydrox-ylates tertiary carbons to form hydroxy compounds [550,831], hydroxylates double bonds to form vicinal diols [707, 296, 555, 577], oxidizes alkenes to a-diketones [560, 567], cleaves double bonds to form carbonyl compounds [840, 842, 552] or carboxylic acids [765, 841, 843, 845, 852, 869, 872, 873, 874], and converts acetylenes into dicarbonyl compounds [848, 856, 864] or carboxylic acids [843, 864], Aromatic rings are degraded to carboxylic acids [575, 576], and side chains in aromatic compounds are oxidized to ketones [566, 577] or carboxylic acids [503, 878, 879, 880, 881, 882, 555]. Primary alcohols [884] and aldehydes [749, 868, 555] are converted into carboxylic acids, secondary alcohols into ketones [749, 839, 844, 863, 865, 886, 887], ketones into keto acids [555, 559, 590] or acids [559, 597], ethers into esters [555], and amines into amides [854, 555] or imines [557], Aromatic amines are oxidized to nitro compounds [755, 559, 592], aliphatic nitro compounds to ketones [562, 567], sulfides to sulfones [846], selenides to selenones [525], and iodo compounds to iodoso compounds [595]. 

Nickel peroxide, an undefined black oxide of nickel, is prepared from nickel sulfate hexahydrate by oxidation in alkaline medium with an ozone-oxygen mixture [929] or with sodium hypochlorite [930, 931, 932, 933]. Its main applications are the oxidation of aromatic side chains to carboxyls [933], of allylic and benzylic alcohols to aldehydes in organic solvents [929, 932] or to acids in aqueous alkaline solutions [929, 930, 932], and of aldehydes to acids [934, the conversion of aldehyde or ketone hydrazones into diazo compounds [935] the dehydrogenative coupling of ketones in the a positions with respect to carbonyl groups [931] and the dehydrogenation of primary amines to nitriles or azo compounds [936]. 

Primary amines are oxidized to azo, azoxy, nitroso, or nitro compounds, depending on the oxidants used. Most of the examples include aromatic amines, because aliphatic amines that have hydrogens on the carbons carrying the amino groups may undergo dehydrogenations to carbonyl compounds, imines, and nitriles (see equations 508-514). 

In this reaction, aniline condensation (via initial addition) occurs with a carbonyl group of the aldehyde formed in the ligand by dehydrogenation of alcohol. The imine intermediate formed is then hydrogenated, releasing the monoalkylated secondary amine product. 

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