Halogenated Pyridine Derivatives from Cycloaddition / Cycloreversion of Oxazinone and Haloalkyne Precursors.

Abstract

This study explores the merged cycloaddition/cycloreversion of 1,4-oxazinone substrates with haloalkyne 2π reaction components. Haloalkynes proved generally competent in the Diels-Alder operation and exerted a small influence on the regioselection of the reaction sequence as compared to the reaction sequence with the derived terminal alkyne precursors. Following tandem cycloreversion and elimination of CO₂, the haloalkynes showed a modest preference for formation of 4-halo pyridine products over 3-halo isomeric variants.