Formation of Amines

The potential for a cyclic system using electroreductive conditions was demonstrated by controlled potential electrolysis of [MoBr NN(CH ) H2 (dppe)2] Br, in thf under N2, which gave iV-aminopyrrolidine and the parent dinitrogen complex trans-[Mo(N2)2(dppe)2] 

Work continued albeit at a lower pace after the above discoveries. For example the formation of N-Si bonds was established in the laboratory of Hidai and in this case a catalytic system was developed for formation of trimethylsilyl species from MejSiCl, using trans-[Mo(N2)2(dppe)2] and other dinitrogen complexes as catalysts (21).  

As I mentioned at the beginning of this article, from the early days at the UNF, the chemists were aware of the versatility of nitrogenase, in that a number of 

However, this work pre-dated the discovery of protonation of dinitrogen in the molybdenum and tungsten complexes and, once this had come to light, we turned our attention to the behaviour of isocyanides and alkynes at those sites that activated dinitrogen to reduction. For isocyanides, the first step was to bind these ligands in place of dinitrogen in the complexes trflns-[M(N2)2(dppe)2], which was done by a displacement reaction [Equation (23)].  

The outcome of these studies was a reasonably coherent picture of reduction of dinitrogen and alternative substrates at a metal site, which appeared to relate at least in principle to nitrogenase action. 

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A simpler nonphosgene process for the manufacture of isocyanates consists of the reaction of amines with carbon dioxide in the presence of an aprotic organic solvent and a nitrogeneous base. The corresponding ammonium carbamate is treated with a dehydrating agent. This concept has been apphed to the synthesis of aromatic and aUphatic isocyanates. The process rehes on the facile formation of amine—carbon dioxide salts using acid haUdes such as phosphoryl chloride [10025-87-3] and thionyl chloride [7719-09-7] (30). 

Dialkyldimethyl and alkyltrknethyl quaternaries can be prepared direcdy from secondary and primary amines as shown ia equations 7 and 8, respectively. This process, known as exhaustive alkylation, is usually not the method of choice on a commercial scale. This technique requires the continuous addition of basic material over the course of the reaction to prevent the formation of amine salts (223,224). Furthermore, products such as inorganic salt and water must be removed from the quaternary. The salt represents a significant disposal problem. 

Formation of Amines. Mono-, di-, and triaEyl amines are prepared by reaction with ammonia. The ratio of reagents determines product distribution with sufficient time and excess of aEyl chloride, tetraaEylammonium chloride [13107-10-3] and triallylamine [102-70-5] predominate. Mixed amines are prepared in similar fashion by using a substituted amine in place of ammonia they may also be prepared with allylamine [107-11-9] and a suitable organic chloride. 

AcCl, MeOH, 95-100% yield. This is a convenient method for generating anhydrous HCl in methanol. These conditions are also used to prepare methyl esters from carboxylic acids and for the formation of amine hydrochlorides. ... 

Amine A-oxides 56 were reduced to amines by carbon disulfide (62CPB969). Tire proposed mechanism involved the formation of amines and dithiiranone (57) from the initial adducts 58 the latter is finally hydrolyzed to CO2 and H2S2 (82BCJ3000). 

Direct oxidation of amides can also lead to Hofmann-type rearrangement with formation of amines or carbamates. One reagent that is used is Pb(02CCH3)4. 

As mentioned above, iridium complexes are also active in the formation of amines via the hydrosilylation/protodesUylation of imines. In the presence of 2 equiv. of HSiEts, the cationic complex [lr bis(pyrazol-l-yl)methane (CO)2][BPh4] (C4) catalyzes the reduction of various imines, including N-alkyl and N-aryl imines and both aldimines and ketimmes. Excellent conversions directly to the amine products were achieved rapidly at room temperature in a methanol solution (Scheme 14.7) [53]. 

Table 14.4 Formation of amines via iridium-catalyzed hydrosilylation and subsequent protodesilylation.

Fig. 11 In situ formation of amine nucleophiles and a,/S-unsaturated carboxamides that react further in thermosetting of hyperbranched dendrimer-polyanhydride nanocomposite thin films...

Oxidation of 2,6-di-te/ -but>l-4-phenylphenoI 20 in the presence of an amino acid ester as the nucleophile leads to the formation of amine protected amino acid derivatives. The protecting group is stable towards bases and can be removed ei-... 

Amine build-up in fish muscle usually results from decarboxylation of amino acids in the muscle by enzymes of bacterial origin. This review will present information on the activity of bacterial decarboxylases and the formation of amines in fish. Mechanisms of decarboxylase action and production of bacterial decarboxylases in fish muscle are discussed. Emphasis is placed upon studies dealing with formation of histidine decarboxylase and histamine. Histamine, because of its involvement in Scombroid food poisoning, has been extensively studied with regard to its formation in fish and fishery products. 

TABLE 15.5. Standard Enthalpy of Formation of Amines (kcal/mol)... 

Hydrolyses Esters and Amides. The plasma, liver, kidney, and intestines contain a wide variety of nonspecific amidases and esterases. These catalyze the metabolism of esters and amides, ultimately leading to the formation of amines, alcohols, and carboxylic acids. Kinetically, amide hydrolysis is much slower than ester hydrolysis. These hydrolyses may exhibit stereoselectivity. 

Explosion Properties. Occurence of detonation within rocket engines employing certain aminated fuels and nitric acid propellants are related to the formation of amine or hydrazine nitrates which tend to decompose explosively under the influence of sudden temp or pressure rises (Ref 51). Tangential-mode rocket motor instabilities were analyzed using 1-dimensional, 2-phase... 

Vigorous reduction may involve the rupture of the N—N linkage with the formation of amine and ammonia. Milder reducing agents yield different products, including hydrazine derivatives, e.g. ... 

In the photocatalytic production of amines from alcohols and ammonia, the efFiciency varied with alcohol structure ethanol > methanol > 2-propanol > t-butanol. A hydrogen atmosphere enhanced the formation of amines, a process which was inhibited by oxygen ... 

Formation of amines from alkenes, carbon monoxide, water, and a nitrogen base was discovered by Reppe who used [Fe(CO)5] to catalyze the process to form amines in low yields 125 199... 

A reaction which is very comparable to that which takes place with hydroxylamine consists in the formation of amine vanadates by the action of vanadium pentoxide on the alkylamines. The simplest of those that have been prepared are 8... 

For the cine amination one would normally consider a mechanism involving the formation of thiophyne. However, several pieces of evidence lead to the rejection of the thiophyne mechanism among them, the marked dependence of product distribution on amide concentration, and the non-formation of aminated product in the reaction of 2-bromo-5-methylthiophene under the same conditions. A normal addition-elimination mechanism (2-bromo -> 3-bromo -> 3-amino) is also invalid since the conversion of 3-bromothiophene to 3-aminothiophene under the same conditions is 200 times slower than the conversion 6f 2-bromothiophene to the 3-amino compound. There is also no evidence from NMR of any initial adduct formation. Considering all these facts, the proposed mechanism (Scheme 164) for cine amination involves attack by amide ion at the /8-position of a di- or tri-bromothiophene to form an aminobromothiophene and subsequent debromination of this species. In support of this is cited the fact that the individual polybromothiophenes are converted to 3-aminothiophene by KNH2 in ammonia. Also, 4-amino-2-bromothiophene (485) has been isolated in the reaction of 2-bromothiophene with sodamide. 

Intermediate in properties between lhe eleclrovalent and covalent bonds discussed above is the semi-covalent hond (also called dative or polarized ionic bond). It is formed when both electrons that constitute the bonding pair are supplied by one of Ihe atoms An example is the formation of amine oxides between tertiary amines and oxygen, in which both electrons are donated by the nitrogen atom. Such bonds naturally exhibit electrical polarity. They are members ol ihe large class of heleropolar bonds characieriz.ed by an unequal distribution of charge due to a displacement of... 

MIGNONAC REACTION. Formation of amines by catalytic hydrogenation of aldehydes and ketones in liquid ammonia and absolute ethanol in [he presence of a nickel catalyst. 

Ammonium carbamate is prepared from dry ice and liquid ammonia [14]. These conditions are very similar to the conditions under which we have observed the formation of amine salts. To some readers, ammonium carbamate may seem to be an exotic compound. In fact, it is manufactured industrially on a multiton scale, because on heating (usually at 100-185°C) ammonium carbamate is converted to urea and water [14-16]. Urea is important for both the agricultural and the plastics industries. The ammonium carbamate is not always isolated during urea preparation. Instead, the reactions are carried out under conditions where the carbamate is just an intermediate. Ammonium carbamate is only moderately stable and it gradually loses ammonia in air. Although the data are sparse, the rate of decomposition of carbamates in solution seems to decrease as the volatility of the parent amine decreases [17]. Free carbamic acids in solution do not decompose spontaneously to free amine and C02. Instead, the acid ionizes by reaction with water the proton is transferred from the hydronium ion to the amine and then decomposition occurs [17]. Acids catalyze the decomposition. 

Heterogeneous hydrogenation of the C=N bond is a very widely used synthetic process with application to small and large-scale reactions. Many of the catalysts described in other sections may also be employed, for example those based on supported rhodium, palladium etc, and Raney Nickel. This area has been reviewed extensively recently192. Hydrogenation of oximes and hydrazones results in formation of amines. Milder conditions can be used for oxime reduction if the ethylaminocarbonyl derivative is prepared in situ prior to reduction276. 

In the dihydroxylation of cyclohexene by Me3N+—O-, catalysed by OsC>4, aromatic amines and aliphatic chelating (TMEDA) or bridging (DABCO, hexamine) amines were found to retard the oxidation, owing to the formation of amine adducts of the dioxomonoglycolatoosmium(VI) ester intermediates, which are more resistant to the further oxidation required for product formation.98 Alkenes derived from Gamer s aldehyde, A-Boc-/V,0-acctonide of the aldehyde of L-serine, may be dihydroxylated by OsC>4 with excellent selectivities that may be explained by A1,3 strain.99... 

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