Nitriles formation from amine complexes

In the formation of microemulsions, both ionic and nonionic surfactants are used. Cosurfactants are alcohols or amines [1,5,6,13,14]. It has been shown [23] that straight chain amines are quite different from their corresponding alkanols as cosurfactant. For example, butylanfine is a more effective one on mass basis than triethylene glycol monobutyl ether. It is because the primary amine head group is more hydrophilic than alcohol, nitrile, carboxylic add, ketone, and aldehyde head groups. In the case of amine cosurfactants, the addition of acid makes the cosurfactant more hydrophilic whereas the addition of base makes it less hydrophilic. The relative degree of hydrophilidty at the oil/water interface determines the volume of microemulsion formation. Microanulsions represent complex phase behavior, and the chemical structure of the cosurfactant has a pivotal role to play on their phase behaviors. 

Apart from complex formation involving metal ions (as discussed in Chapter 4), crown ethers have been shown to associate with a variety of both charged and uncharged guest molecules. Typical guests include ammonium salts, the guanidinium ion, diazonium salts, water, alcohols, amines, molecular halogens, substituted hydrazines, p-toluene sulfonic acid, phenols, thiols and nitriles. 

Platinum-catalyzed hydrolytic amidation of unactivated nitriles was reported by Cobley and coauthors. The platinum(ii) complex, [(Me2PO- H- PMe2)PtH (PMe2OH)], efficiently catalyzes the direct conversion of unactivated nitriles into N-substituted amides with both primary and secondary amines. Possible mechanisms for this reaction are discussed and evidence for initial amidine formation is reported. Isolated yields vary from 51 to 89% [25]. 

The mode of deaetivation was also different between the two eatalysts the siliea eatalyst underwent a slow, irreversible formation of surfaee-bound amide groups (arising from the reaetion of the surfaee-bound primary amine and the ester funetion of the ethyl eyanoaeetate) in eontrast, the MCM-41 reeovered spent eatalyst did not display bands for nitrile or amide groups, but rather the presenee of some adsorbed complex organie eompounds. 

Catalytic hydrogenation of nitriles is a complex process that can yield several final products deriving from a mechanism that assumes the formation of a key imine intermediate 1 as the first step . Hydrogenation of imine 1 affords the usually desired primary amine 2. Addition of imine 1 and newly formed amine 2 gives a-amino amine 3, which can yield secondary amine 4 directly by hydrogenolysis, or it eliminates a molecule of ammonia to afford the Schiff base 5. This imine can be isolated when sterically hindered, or hydrogenated to secondary amine 4. 

Benzylic carbocations are also stabilized by complexation to chromium and a number of interesting reactions have been reported. Again, reaction of the carbocations with nucleophiles occurs from the exo face of the complex, relative to the metal. Carbocations are readily formed by treatment of benzylic alcohols with a strong acid, such as sulfuric acid, tetrafluoroboric acid, or borontrifluoride etherate. The cation can be trapped with water, alcohols, nitriles, and mono-or disubstituted amines to form alcohols, ethers, amides, and di- or trisubstituted amines respectively. Scheme 96 illustrates the formation of a benzylic carbocation followed by intramolecular trapping, resulting in a net inversion of stereochemistry. Benzylic acetates react with trimethyl aluminium introducing a methyl group from the opposite face of the metal. 

Formation of ruthenium(m) complexes by attack at co-ordinated amines promises to be a useful synthetic method. Recent examples include the reactions of the [Ru(NH3)e] + ion with aldehydes (RCHO) to give the corresponding co-ordinated nitrile, [Ru(NH8)6(NCR)] + (R = Me or Ph, and the oxidant is unknown), or the reaction with glyoxal, MeCOCOMe, in the presence of hydroxide ion to give the ion (45). From kinetic studies of the latter reaction, a mechanism is proposed in which the [Ru(NH3)sNH2] ion attacks at one carbonyl centre of MeCOCOMe, followed by further deprotonation of the cis ammonia molecule, cyclization, and elimi-... 

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