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Synthesis of 1,2-Dihydropyridines Using Vinyloxiranes as Masked Dienolates in Imino-Aldol Reactions

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posted on 03.08.2006, 00:00 by Bernhard Brunner, Nicole Stogaitis, Mark Lautens
The application of vinyloxiranes, substituted with an electron-withdrawing group, as masked dienolates in vinylogous imino-aldol reactions was achieved. Under the reaction conditions highly substituted 1,2-dihydropyridines were obtained in moderate to good yields. Mechanistic studies indicate that the reaction proceeds via the formation of an (E)-amino-α,β-unsaturated aldehyde, followed by isomerization to the (Z)-isomer, cyclization, and elimination of a water molecule, leading to the formation of the 1,2-dihydropyridine.