DIENE-TRANSMISSIVE HETERO-DIELS-ALDER CYCLOADDITION USING CROSS-CONJUGATEDIOXATRIENES: A NOVEL SYNTHESIS OF TETRAHYDROPYRAN-FUSED AZA- AND THIA-HETEROCYCLES

摘要

The diene-transmissive hetero-Diels-Alder methodology using cross-conjugated dioxatrienes [2-(R-methylene)propanedials] has been developed. The initial cycloaddition with electron-rich dienophiles, followed by the reactions of the resulting 1-oxadiene moiety of the monoadducts with amines and Lawesson's reagent generated 1-azadienes and 1-thiadienes. The second hetero-Diels-Alder reaction of these reactive heterodienes with dienophiles (tosyl isocyanate, diphenylketene, enones, and maleinimide) produced pyran-fused aza-and thiaheterocycles, providing a new synthetic method for these heterocycles.