ChemInform Abstract: Anomer Controlled Substitution Reactions with Some N-Alkylyridinium Compounds.

ChemInform Abstract

The results of semiempirical MNDO calculations on bond lengths, heats of formation, and net atomic charges of compounds (I) and (II) allow general trends to be recognized. These trends allow the prediction of important reactivity characteristics for this series of compounds and provide the motivation for the synthesis of compounds (VI), (XII) and (XV) and for tests of their usefulness. Specifically, the out-of-ring C-N bond length serves as a useful criterion for the reactivity with nucleophilic partners. Whereas "normal" N-alkylpyridinium salts are hardly ever attacked in the α position, the preparative utility of this structural element can now be considerably increased by use of the anomeric effect resulting in a long out-of-ring C-N bond. So the pyridine moiety can either be split off in nucleophilic substitutions at the alkyl in N-alkylpyridinium salts or not depending on the substitution in the starting N-alkylpyridinium molecule (and, hence, the anomeric effect) and the nucleophile itself (examples see scheme).