Synthesis of the C-2 Functionalized 1,4-Dihydropyridines

Abstract

Unsymmetrical 1,4-dihydropyridine esters 4 and 5 were synthesized from the symmetrical precursor 1 through the intermediacy of 2-bromomethyl derivative 2. Then reaction of isothiouronium salt 4 with electrophilic specie, methyl iodide, in the presence of base produced S-methylated derivative 6. Reaction of the dibrominated derivative 3 with lithium salt of 1,3-dithiane led to the formation of dithio acetal derivative 7.