New Diels-Alder Reactions of (–)-Thebaine and First X-Ray Crystallographic Structure Analyses of the Cycloadducts

Diels-Alder reactions of (-)-thebaine (1) as an electron-rich diene system with acceptorsubstituted ethenes gave rise to the cycloadducts 2, 3, and 4 in high regio- and stereoselectivities. Structural analyses were performed by high resolution NMR spectroscopy and, for the first time in the thebaine cycloadduct series, by X-ray crystallographic structural analyses of the compounds 2, 3a, and 3b. In the reaction of (-)-thebaine (1) with an in situ generated aryne, the anellated azocine derivative 5 was formed.