Action of Base on Certain Pyridinium Salts^1,2

Chemistry of dihydropyridines

“…Treatment of 3-substituted pyridinium salts with hydroxide ion has been described by several workers.69,219,2 26,2 47 The products were too unstable for isolation and tentative structure assignments were made on the basis of uv spectra. 219•226 The action of aqueous sodium hydroxide on the nicotinamide salt 52 gave a product formulated69 as 57 (for another dimer of similar structure see ref 219). On treatment of 57 with ethanol a cyclic trimer was formed.69 CN The pseudo base 58, prepared from the corresponding pyridinium salt, could be isolated.222•223 The structure of an analogous compound derived from a 3,5-diacetyl-l ,4-diphenylpyridinium salt has not been established with certainty.…”

“…Early workers found that dihydropyridines could be degraded by the action of concentrated acid or alkali.1'47, 404'594 The Hantzsch esters on treatment with alkali gave the cyclohexenones 219 by ring-opening to 1,5-diketones followed by intramolecular aldol condensation47'404•443'594'595 (see also ref 596). 219 Hydroxylamine opens the dihydropyridine ring in a number of instances49'280'401 '422'442 with the formation, usually, of the dioxime derived from the resulting 1,5-diketone.…”

Is Simpler Better? Synthetic Nicotinamide Cofactor Analogues for Redox Chemistry

“…54−57 The group of Steckhan was the first to report chemically driven metalcatalyzed regeneration of NAD(P)H using formate as an electron source to generate [Cp*Rh(bpy)H] + in situ. 57 In terms of chemical and physical properties, the reaction of mNADHs and their pyridinium salt derivatives with alkali 58,59 and acid 60−64 has been extensively documented. 11,65 The stability of the natural and substituted pyridinium ions and their 1,4-dihydro reduction products in aqueous buffers was also largely reported.…”

Characterization studies of 1-(4-cyano-2-oxo-1,2-dihydro-1-pyridyl)-3-(4-cyano-1,2-dihydro-1-pyridyl)propane formed from the reaction of hydroxide Ion with 1,3-Bis-(4-cyano pyridinium)propane

“…In addition, an unstable compound at room temperature with two pyridine rings connected by oxygen was found in the alkaline hydrolysis of 1-benzyl-3-acetylpyridinium chloride. 13,14,19 This noncyclic ether is similar to compound 4. These facts suggest the conversion of the intermediate cyclic ether into 4 through an internal rearrangement.…”