A short total synthesis of cerpegin by intramolecular hetero Dials-Alder cycloaddition reaction of an acetylene tethered pyrimidine

The electron poor 4,6-dichloropyrimidine-5-carbaldehyde, which is readily a vailable, is used as a starting material for the synthesis of fused 2-chlor opyridines. Chlorination transforms the aldehyde into the corresponding aci d chloride, which can be functionalized with acetylene tethers. Intramolecu lar hetero Diels-Alder reactions at elevated temperatures afford the fused pyridines in varying yield. This reaction sequence was applied to the total synthesis of cerpegin.