Reactions with amine salts

Reaction with arenediazonium salts Adding a phe nol to a solution of a diazonium salt formed from a primary aromatic amine leads to formation of an azo compound The reaction is carried out at a pH such that a significant portion of the phenol is pres ent as its phenoxide ion The diazonium ion acts as an electrophile toward the strongly activated ring of the phenoxide ion... 

The addition of alkyl haUdes to phosphines is analogous to the reactions with amines. Because primary phosphonium salts are highly dissociated, the reaction proceeds to the tertiary or quartemary salts. 

Later in the 20th century, Vompe and Stepanov delineated efficient procedures for the preparation of the so-called Zincke salts (e.g., 1) from pyridines and 2,4-dinitrochlorobenzene, involving, for example, reflux in acetone. Vompe and Lukes also noted that electron-donating substituents on the pyridinium ring of the Zincke salt retarded reaction with amines at the 2-position of the pyridinium ring, sometimes leading instead to attack at the C-1 position of the 2,4-dinitrobenzene ring, with displacement of the pyridine. 

In addition to their reactions with amines, Zincke salts also combine with other nitrogen nucleophiles, providing various A -substituted pyridine derivatives. Pyridine A -oxides result from the reaction with hydroxylamine, as exemplified for the conversion of Zincke salt 38 to the A -oxide 39 Reactions of Zincke salts with hydrazine, meanwhile, lead... 

The configuration of the amine was retained, except in the case of amino acid derivatives, which racemized at the stage of the pyridinium salt product. Control experiments showed that, while the starting amino acid was configurationally stable under the reaction conditions, the pyridinium salt readily underwent deuterium exchange at the rz-position in D2O. In another early example, optically active amino alcohol 73 and amino acetate 74 provided chiral 1,4-dihydronicotinamide precursors 75 and 76, respectively, upon reaction with Zincke salt 8 (Scheme 8.4.24). The 1,4-dihydro forms of 75 and 76 were used in studies on the asymmetric reduction of rz,>S-unsaturated iminium salts. 

Coupling reactions with diazonium salts to yield intensely colored azo derivatives have often been used for the detection of phenols, primary aromatic amines and electron-rich heterocyclics. 

Reactions of Metal Compounds with Amine Salts... 

The oxides have been converted to the trihalides by reaction with amine hydrohalides with mp <200°C (e.g., PhNH2, MeNH2, Me2NH, EtNH2, Et NH, etc.). A double salt was formed from the reaction with the hydrohalide, which served both as solvent and halogenating agent. The reaction mixture was heated to vaporize the solvent and decompose the double salt, leaving the anhydrous halide (85). 

Unsymmetrically substituted perylene pigments are a comparatively recent novelty. Selective protonation of the tetra sodium salt of perylene tetracarboxylic acid affords the monosodium salt of perylene tetracarboxylic monoanhydride in high yield. Stepwise reaction with amines produces unsymmetrically substituted perylene pigments [2],... 

In the above reactions, aromatic amine salts give better results than the free bases 14, 15), which are indeed reported to fail to react with cyanoguanidine (777). Aliphatic amines react more smoothly in the presence of some free amine 14,15). As aromatic amine salts dissociate to a much larger extent than do aliphatic amine salts, it is believed 14,15), that a considerable amount of free aromatic amine is present in the reaction mixture. Since Curd and Rose 148) have also shown that use of (100%) free aliphatic amine lowered the yields of biguanides, a mixture of free amine and amine salt would appear to be most favourable for biguanide formation. 

Reaction With Amine Acid Salts. A reaction which appears to be less well-appreciated Is the ready condensation of some amlnoplasts with simple amines to selectively generate secondary and tertiary amine linked condensates (Scheme 7). Even In the presence of excess ammonia or primary amine, crosslinked products 13 (plus, conceivably, a trisubstituted product) which contain more highly substituted secondary (and tertiary) amines predominate over 12 (H). These particularly stable, high crosslink density products form with simple amine or diamine acid salts under unexpectedly mild, even room temperature conditions (6). 

The A-acetyl derivatives of the 2-alkylthio-l,3-thiadiazol-4-imines (124, R = SR, R = Ac) undergo nucleophilic displacement reaction with amines (benzylamine, cyclohexylamine, morpholine, or aniline) giving the 2-amino derivatives (124, R = NRj, R = Ac). The salt (126, R = R = Ph, R = R = H, X = Cl) reacts with aniline at room temperature giving 4-anilino-2-phenyl-l,3-thiazole (128), presumably by a mechanism involving cleavage of the heterocyclic ring. ... 

Elguero and Espada29S have used this dealkylation reaction with quaternary salts of heterocyclic compounds. Another application is the preparation of tertiary amines functionalized in the <5 position.296 In these reactions, the ammonium salt 196 is both the catalyst and the reagent. 

Similarly, ammonia and amines (e.g. PhNH2, Me2NH) give initial adducts of type (589), which are then oxidized (with air, Br2, etc.) to new onium salts (590). The adduct with cyanide ion tautomerizes to (588) phenothiazonium chloride forms (591) via a similar addition and tautomerism (HCI-H20, 100°C). Repeated reaction with amines gives products of type (592). 

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