Intramolecular N-acyliminium ion-olefin cyclization in the synthesis of optically pure isoquinoline derivatives: Control of stereochemistry and application to synthesis of morphine alkaloids

Article abstract of DOI:10.1135/cccc19990203

The 3-[2-(cyclohex-1-enyl)ethyl]-[1,3]oxazoline-2,4-dione derivatives 9, 14 and 16 were subjected to hydride reduction followed by acid-catalyzed olefin-N-acyliminium ion cyclization to afford a series of perhydroisoquinolines 10, 11a, 11b, 19a-19c, 20a, 20b and 21. A mechanism was proposed that accounts for the observed stereoselectivity of the cyclization reactions based on the neighboring group participation by a benzoate group.