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RESEARCH PRODUCT

Isomerization and Application of Aroylnorbornenecarboxylic Acids for Stereoselective Preparation of Heterocycles

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description

When boiled in acidic or basic solution, diendo-3-aroylbicyclo[2.2.1]heptane-2-carboxylic acids (1 and la) isomerize to exo-3-aroylbicyclo[2.2.1]heptane-endo-2-carboxylic acids (2 and 2a). Similar endo→exo and even exo → endo isomerization of the aroyl group occurred when the Diels-Alder product containing a mixture of 3-exo-p-toluoylbicyclo[2.2.1 ]hept-5-ene-2-endo-carboxylic acid (4) and 3-endo-p-toluoylbicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid (5) was reacted with bifunctional reagents: o-aminothiophenol, 3-amino-1-propanol, 1,4-diaminobutane or diexo-3-hydroxymethylbicyclo[2.2.1]heptane-2-amine. All the reactions yielded mixtures of norbornene diendo- and diexo-fused heterocycles (6) and (7, 8 and 10, 9 and 11, or 12 and 13), which were separated and whose structures were established by means of IR, 1 H- and 1 3 C-NMR spectroscopy, with DIFFNOE, 2D-COSY, DEPT, HMQC and HMBC measurements.