Polysubstituted\nPyridines from 1,4-Oxazinone Precursors

This study describes a general method for the preparation\nof 1,4-oxazin-2-one\nintermediates from acetylene dicarboxylate and β-amino alcohol\nprecursors. Oxazinones prepared in this manner were employed in a\ntandem cycloaddition/cycloreversion reaction sequence with a model\nalkyne (phenyl acetylene) to give substituted pyridine products. Fundamental\nreactivity and selectivity studies are complemented by the synthesis\nof the polycyclic ergot alkaloid natural product xylanigripone A.