Solid state oxidation of 1,4-dihydropyridines to pyridines using phenyliodine(III) bis(trifluoroacetate) or elemental sulfur

Abstract

A solventless oxidation of 1,4-dihydropyridines is effected by phenyliodine(III) bis(trifluoroacetate) (PIFA) at room temperature or elemental sulfur under microwave irradiation conditions. Dealkylation at the 4-position in the cases of ethyl, isopropyl and benzyl substituted dihydropyridine derivatives with PIFA is circumvented by an alternative general procedure using elemental sulfur which provides pyridines in good yields.