Preparation and Conversion of N-Halomethylpyridinium Halides. Comparison with Related Compounds

Abstract

N-Halomethylpyridinium halides 1a-f (X-CH(2)Py(+)X(-), X = Cl, Br) have been synthesized from a three-component reaction mixture containing a thionyl halide 5, formaldehyde (6), and a pyridine 7. The salts 1a-f react readily with a variety of heterocyclic nucleophiles to yield (in general, nonsymmetrical) 1,1-bis(heteroarylium)methyl salts 2ea-hb, (pathway a). The use of trichloroacetaldehyde (9) instead of formaldehyde in this three-component reaction leads to a salt 10 in which one of the CH(2)-hydrogens was replaced by the electron-withdrawing CCl(3) substituent. This changes the standard reaction pathway a of 1 in solution toward nucleophiles completely: the chlorinated N-vinylpyridinium salts 11 and 12 were formed after the reaction of 10 with pyridine or triphenylphosphane. These are useful intermediates for the synthesis of new N- and 4-substituted 1,4-dihydropyridines 13-15 as could be demonstrated for compound 11. To explain the reactivity pattern of compounds 1 and 10 and the related structures (MeO-CH(2)Py(+), 16, and Me(3)SiO-CH(2)Py(+), 17) we calculated, using ab initio and DFT methods, reaction pathways a and b, both in the gas phase and in solution using ammonia as a model nucleophile. For all of these compounds, pyridine displacement (pathway b) dominates in the gas phase. As an example the energy gap between these two transition states for 1a turns out to be relatively small (11.6 kcal/mol in favor of pathway b, TS2). Solvation effects can therefore stabilize the corresponding transition state TS1 more effectively. In a MeCN solution, TS1 is 1.6 kcal/mol less energetic than TS2.

Charged tag founded in N-(1-chloroalkyl)pyridinium quaternization for quantification of fatty aldehydes

“…2b). Carbon-nitrogen bond of derivatives has been demonstrated to be longer than the carbon-carbon bond [50][51][52]. Thus derivatives fragmented in this similar manner.…”

2-Amino-5-methyl-1,3,4-thiadiazole and 2-amino-5-ethyl-1,3,4-thiadiazole

“…Similarly, in the structures of the HBr (Antolini et al, 1993) and HCl±hydrate salts of 2-amino-5methyl-1,3,4-thiadiazole (Pilz et al, 1998), the halides are involved in the hydrogen-bonding network. Larger substituents, such as those containing phenyl rings (Foresti et al, 1985;Molina et al, 1988;Leung et al, 1992;Anders et al, 1999), affect the molecular packing by their very size. Thus, the structures of 2-amino-1,3,4-thiadiazoles with simple nonhydrogen-bonding substituents, namely, 2-amino-5-methyl-1,3,4-thiadiazole, (I), and 2-amino-5-ethyl-1,3,4-thiadiazole, (II), have been investigated to elucidate the in¯uence of these substituents on the molecular packing observed in the parent thiadiazole.…”

Synthesis of Unusually Substituted Ureas Starting from Bis(1,3,4‐thiadiazolo)‐1,3,5‐triazinium Halides via Oxo‐imidothioate Zwitterions

“…[1,2] The N-(1-haloalkyl)pyridinium halides were obtained in one pot by the reaction of a 1:1:1 molar ratio of aldehyde/ thionyl halide/pyridine (Scheme 1). [10][11][12] Scheme 1. Formation of 1 via bromomethylpyridinium bromide.…”