Divergent change of regioselectivity in nucleophilic addition of electron deficient allylic tin reagents to 4-acylpyridinium salts; selective formation of 4,4-disubstituted 1,4-dihydropyridines

Abstract

Nucleophilic additions of 2-methoxycarbonyl- and 2-cyano-allyltributyltins to 4-methoxycarbonyl-, 4-formyl-, and 4-acetyl-pyridines activated by methyl chloroformate afford 1,4-adducts exclusively or predominantly, while the reactions of 2-methylallyltributyltin with 4-methoxycarbonyl-and 4-acetyl-pyridines activated by methyl chloroformate give the 1,2-adducts exclusively.