Heterocycles in organic synthesis. Part 6. Nucleophilic displacements of primary amino-groups via 2,4,6-triphenylpyridinium salts

Abstract

Benzylamine and 2-, 3-, and 4-pyridylmethylamine are readily converted into the corresponding 1 -substituted 2.4.6triphenylpyridinium cations, from which 2.4.6-triphenylpyridine is displaced in high yield by a variety of nucleophiles. This synthetic method avoids the use of unstable and obnoxious pyridylmethyl halides and shows steric selectivity of significance in the conversion of secondary into tertiary amines by alkylation.

Transformations of 2-alkylidene-4-oxothiazolidine vinyl bromides initiated by bromophilic attack of neutral and anionic nucleophiles

“…In spite of the fact that pyridine is a relatively poor leaving group and susceptibility of the pyridinium ring to nucleophilic attack at the 2-, 4-and 6-positions, 29 and in some cases was followed by ring cleavage, 30 we have demonstrated that the pyridinium salts 21 are excellent substrates for substitution reactions with these neutral nucleophiles.…”

2-Alkylidene-4-oxothiazolidine Vinyl Bromides: Versatile Precursors for C(5) Functionalization via Pyridine-Assisted Bromine Transfer

“…Spectroscopic data and elemental analyses were consistent with the structures 9-11. 29 Despite the fact that pyridine is a poor leaving group and that the pyridinium ring is susceptible to nucleophilic attack at the 2-, 4-and 6-positions, 30 in some cases followed by ring cleavage, 31,32 we did not observe a decrease in effectiveness of these substitution reactions affording new 5-amino and 5-alkoxy-2-alkylidene-4oxothiazolidines.…”

Preparation and nucleophilic substitution of the 2,4,6-triphenylpyridinium salts, diazonium intermediates and N,N-1,2-benzenedisulfonylimides of chiral amino acids

“…Inversion of amino acids via 2,4,6triphenylpyridinium salts The first attempt in the effort to invert the L-"-amino acids to their D-isomers was the u s e o f 2,4,6-triphenylpyridinium derivatives. These compounds are known to be valuable intermediates in nucleophilic substitution of primary and secondary amines (Katritzky et al 1979, Katritzky et al 1983. We have recently reported their use in inversion of chiral amines (Said and Fiksdahl 2001b).…”