Diels-Alder reactions of R-(-)-carvone with isoprene using different Lewis acids as catalysts have been studied. The best results were obtained with EtAlCl2 at 25 °C for 48 hours. The yields are quantitative and the d.e. is 86.8%. Regioselective dihydroxylation at the endocyclic double bond of the cycloadduct followed by acetonation gave a crystalline acetonide, the structure and stereochemistry of which were confirmed by an X-ray crystallographic analysis. Hence the stereochemical outcome of the Diels- Alder reaction is now established and the reaction occurred preponderantly in an anti orientation with respect to the isopropylene group in R-(-)-carvone.
ASJC Scopus subject areas