Secondary amine cation

Photoinduced oxidation of amines leads to the formation of amine radical cations. These intermediates display both radical and cationic character with the N-H protons of the primary and secondary amine cation radicals being acidic. As a result, an efficient deprotonation occurs at the carbon a to the nitrogen radical cation giving aminyl radicals (Eq. (3)) [100]. 

The yellow [S4N5] anion (5.26) was first reported in 1975 from the methanolysis of Me3SiNSNSiMc3. It can also be prepared by the treatment of S4N4 with certain nucleophiles, e.g., secondary amines or azide salts of small alkali metal cations (Eq. 5.16). The reaction of (NSC1)3 with dry liquid ammonia at -78°C also generates [NH4][S4N5] in ca. 50% yield." ... 

The alleged preparation of the supposed cobalt(II) complex Na[Co(Et2dtc)3] described by D Ascenzo and Wendlandt (305) has been repeated by Holah and Murphy (306), who identified the product as [Co(Et2dtc)3]. Complexes of cobalt(III), nickel(II), and palladium(II) salts with cationic, dithiocarbamate ligands have been synthesized (307). Reaction of the secondary amine (Et2N(CH2)2)2NH with CS2 produces... 

Nitrosation also occurs with secondary amines but stops at the stable N-nitroso stage, R2N—N=0. Tertiary aliphatic amines are converted initially into the nitrosotrialkylammonium cation,... 

Summary New lyophilic cationic silicone surfactants have been synthesized by direct quatemization of halogenated siloxanyl precursors or by transformation of these precursors into tertiary amines with a subsequent quatemization step. After transformation of the precursors into secondary amines, reaction with maleic anhydride and neutralization, new anionic products were obtained. 

Figure 4.24 Two amine-containing molecules can be crosslinked by formaldehyde through formation of a quaternary ammonium salt with subsequent dehydration to an immonium cation intermediate. This active species then can react with a second amine compound to form stable secondary amine bonds.

Figure 28.4 Formaldehyde can be used to capture protein interactions if it is used at low concentrations. The reaction proceeds through modification of a protein to create an intermediate immonium cation, which then goes on to react with a neighboring protein to form the crosslinked product via secondary amine bonds.

Phosphorous acid has also been of use for additions to imines. Originally investigated by Moedritzer and Irani,241 who developed a Mannich-type procedure for the preparation of phosphorus-centered species, the approach was found later to be useful for both primary and secondary amines in reaction with formaldehyde and phosphorous acid. The approach was later used for the preparation of a cationic exchange resin using a polymer substrate.242... 

The primary, secondary, and tertiary aliphatic amines do not form simple addition complex ions with bare transition metal ions. Only Ag+ reacts with MeNH2 to form a simple addition product [AgMeNH2]+ (107). The Pb+ ion also forms addition products, [PbMeNH2]+ and [Pb(MeNH2)2]+, with methylamine (143). Other bare transition metal ions (144) react with amines via removal of one hydrogen to form the metal hydride and the amine cation with one hydrogen removed [RR N]+. 

The products from benzotriazole, aldehydes and primary or secondary amines exist in the melt or in solution as equilibrium mixtures of 1- and 2-benzotriazolyl compounds, 99 and 100, whereas the solids are 1-benzotriazoles 99115. The equilibrium involves the resonance-stabilized aminomethyl cation and the delocalized benzotriazolide anion it accounts for the ease with which the bond attached to the benzotriazole moiety is cleaved. 

FDMR has also been used to detect the transient radical cations formed from secondary amines by pulse radiolysis. As mentioned earlier this technique has been used to study a variety of systems such as the radical cation of triethylamine. The radical cations of diethylamine, n-propyl amine and f-butylamine, have also been studied25. The results have shown that the FDMR signal is enhanced with increasing alkyl substitution of the amine as in the pyrrolidines (18) and the piperidines (19)25. 

Under favourable circumstances, the initially formed /V-ylid reacts further through C-N cleavage. Thus, in the presence of a strong nucleophile, such as a phenoxide anion, the quaternary dichloromethylammonium cation forms an ion-pair with the phenoxide anion (Scheme 7.27), which decomposes to yield the alkyl aryl ether and the /V-formyl derivative of the secondary amine [22, 23]. Although no sound rationale is available, the reaction appears to be favoured by the presence of bulky groups at the 4-position of the aryl ring. In the absence of the bulky substituents, the Reimer-Tiemann reaction products are formed, either through the breakdown of the ion-pair, or by the more direct attack of dichlorocarbene upon the phenoxide anion [22,23],... 

The cyclic metabolite 11.169 was also a substrate in further biotransformations, being (V-demethylated to the corresponding endocyclic imine, and oxidized to phenolic metabolites. Very little if any of the secondary amine metabolite (11.168) appeared to undergo direct (V-demethylation to the primary amine, in contrast to many other tertiary amines, presumably due to very rapid cyclization of the secondary amine facilitated by steric and electronic factors. The possibility for the iminium cation (11.169 H+) to become deprotonated (a reaction impossible for the iminium 11.166 in Fig. 11.20) should also drive the cyclization reaction. 

Amines and amides undergo oxidation at or adjacent to nitrogen (Scheme 27). A neutral amine, for example, can be oxidized to afford a cation radical (117 to 116). Similarly, electrooxidation of the anion produced via deprotonation of a secondary amine leads to an aminyl radical (119) that is capable of participating in carbon-nitrogen bond-forming reactions with remotely tethered alkenes. 

Anodic oxidations of secondary amines can provide radicals or radical cations. 

Ingemann, S. Hammerum, S. Derrick, P.J. Secondary Hydrogen Isotope Effects on Simple Cleavage Reactions in the Gas Phase The a-Cleavage of Tertiary Amine Cation Radicals. J. Am. Chem. Soc. 1988, 770,3869-3873. 

Here the authors found that the penicillin anion (P ) could be extracted efficiently with a secondary amine (Amberlite LA-2) in the pH range 5-7 where the product is most stable. This type of process is used extensively in hydrometallurgy (Chapter 11) and can be used to extract both anionic species using cations as shown earlier, or cationic species using organic acid anions. In hydrometallurgy, the system normally uses a hydrocarbon diluent, but for pharmaceutical applications more polar diluents are generally required. 

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