Nucleophilic\nDearomatization of Activated Pyridines\nUsing Vinyl Sulfoxonium Ylides: Application to the Synthesis of <i>Bis</i>-Heterocycles

A highly\nefficient method has been developed for synthesizing 4-dienyl\ndihydropyridines through the nucleophilic dearomatization of activated\npyridines using vinyl sulfoxonium ylides. This reaction follows the\nsequence involving ylide addition to activated pyridine, [2,3]-sigmatropic\nrearrangement, and subsequent sulfenic acid elimination. The resulting\n4-dienyl dihydropyridines are then used in the synthesis of highly\nsubstituted <i>bis</i>-heterocyles. Control experiments\nand quantum chemical calculations were conducted to elucidate the\nselectivity and the mechanistic pathway.