Isomerization and Application of Aroylnorbornene-Carboxylic Acids for Stereoselective Preparation of Heterocycles

摘要

When boiled in acidic or basic solution, diendo-3-aroylibicyclo[2,2.1]heptane-2-carboxylic acids (1 and 1a) isomerize to exo-3-aroylibicyclo[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, ~1H - and ~13C-NMR spectroscopy, with DIFFNOE, 2D-COSY, DEPT, HMQC and HMBC measurements.