Amines mechanism

NCA polymerization by secondary amines may involve the amine or activated monomer mechanisms or both mechanisms simultaneously. Unhindered secondary amines such as dimethylamine and piperidine react like primary amines, and polymerization occurs by the amine mechanism. Polymerization by slightly hindered amines such as diethylamine, N-methylbenzylamine, and di-n-propylamine involves a combination of the amine and activated monomer mechanisms. More hindered secondary amines, such as di-n-isopropylamine and dicyclohexylamine, react almost exclusively via the activated monomer mechanism. 

Hess HA, Roper JC, Grill SW, Koelle MR (2004) RGS-7 completes a receptor-independent heterotrimeric G protein cycle to asymmetrically regulate mitotic spindle positioning in C. elegans. Cell 119 209-218 Higashijima T, Burnier J, Ross EM (1990) Regulation of Gi and Go by mastoparan, related amphiphilic peptides, and hydrophobic amines mechanism and structural determinants of activity. J Biol Chem 265 14176-14186... 

A variety of amination mechanisms have been recognized, some of which imply the formation of a-adducts as reaction intermediates.10 4... 

The amination reaction carried out at -33°C gives a mixture consisting of 4-amino-, 8-amino-, and 2-amino-1,7-naphthyridine, 4-amino-2-methyl-1,3,7-triazanaphthalene, and some unsubstituted 1,7-naphthyridine. The composition of this mixture is not related to that of the adducts described above in any simple way. Adducts 54 and 56 are suggested to be involved in the formation of the 8-amino and 4-amino derivatives, respectively, by a tele-amination mechanism.111 Scheme 3 illustrates one of these proposed paths. 

Under these conditions the amination reaction yields a mixture of 2-amino- and 8-amino-1,7-naphthyridines in a nearly 1 1 ratio. Here again the observed a-adduct is responsible for the formation of only one of the products, the 2-amino compound, which arises by a tele amination mechanism. The other amine requires some other as yet undetected a-adduct.111... 

Lemberger L, Rowe H, Carmichael R, Crabtree R. Clinical studies with drugs affecting biogenic amine mechanisms. Catecholamines Basic clinical frontiers. In Proceedings, 4th International Catecholamine Symposium, 1979, part 2, pp. 1923-1924. 

The nitroazoles are widely used in the reaction of vicarious nucleophilic substitution of hydrogen. Vicarious nucleophilic C-amination is, practically, the single method of direct introduction of the amino group into nitro compounds. Using the vicarious nucleophilic substitution reaction we have successfully carried out the C-amination of some representatives of nitrobenzazoles, nitroazoles, and model compounds thereof and studied the structure of aminated products and the C-amination mechanism [673-678],... 

Lithium aluminium hydride reduces amides to amines. Mechanism of LiAlH4 reduction of amides is given in Scheme 6.11. 

Scheme 8 Modified amination mechanism involving amine coordination prior to oxidative addition...

Pyrazines have been prepared by heating 1,2-dicarbonyl compounds with a-amino acids. Thus Rizzi (308) observed that under the conditions of the Strecker degradation, equimolar amounts of DL-valine (44) and butane-2,3-dione in refluxing bis(2-methoxyethyl) ether, diglyme, gave isobutyraldehyde, tetra-methylpyrazine (9%), and a mixture of cis- and trans-2-isopropyl-4,5-dimethyl-3-oxazoline (4%). He proposed a reductive amination mechanism in which butane-23-dione was converted to 2-aminobutan-3-one which underwent self-condensation to the pyrazine. Tetramethylpyrazine was also prepared when the same reactants were heated in dimethylformamide at 123° for 5 hours (and other pyrazines prepared similarly) (308a). 

The occurrence of general acid-catalyzed hydroxylaminolysis or methoxylaminolysis of thiol esters or amides has been described in Section IIB in terms of kinetically important tetrahedral intermediates. Two kinetically indistinguishable mechanisms for general acid-catalyzed aminolysis reactions are represented by transition states 42 and 43. Mechanism 42 involves a prior protonation of the ester followed by a general base-catalyzed aminolysis mechanism 43 is a general acid-assisted nucleophilic reaction of the amine. Mechanism 42 can be ruled out in the hydrazinolysis of phenyl acetates (Bruice and Benkovic, 1964) and in the hydrazinolysis of S-thiolvalerolactone (Bruice et al., 1963) on the basis of a calculated rate constant which is greater than the diffusion-controlled limit. Mechanism 43 is therefore correct. 

FIGURE 12.7 Base catalyzed hydrolysis of this class of pentaaminecobalt(lll) complex is believed to proceed via a pseudo-aminate mechanism via deprotonation of the blue hydrogen atoms. 

Figure 4.2 Initiation and growing steps of a primary amine-initiated ROP of NCAs (a) amine mechanism (b) activated monomer mechanism.

Messman and coworkers did a mechanistic study of a-amino acid carboxy anhydride polymerization [158] They polymerization in high vacuum with polymerization at atmospheric The conclusion of their work was that poly(O-benzyl-L-tyrosine) prepared in vacuum yields a polymer by normal amine mechanism with minimum termination. By contrast when the reaction was not carried out at high vacuum, there were several termination products. 

Neumann H. Aromatic amines mechanisms of carcinogenesis and imphcations for risk assessment. Eront Biosci Landmark Ed 2010 15 1119-1130. 

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