Transition-metal-mediated exo-selective diels-alder reactions for the preparation of octalones with unusual stereochemistries.

摘要

2-Cobaloxime-(E)-1,3-pentadienyl complexes (cobaloxime=pyridine(dimethylglyoxime)_2cobalt(III_)) react with a variety of cyclohexenones in [4+2] cycloaddition reactions. These cycloaddition reactions produce octalones with cis ring junctions through exo transition states. The octalones are removed from the cobalt via demetalation reactions that replace the cobalt with a hydrogen and provide pyr(dmg)2CoMe, which can be recycled into the synthesis of the starting dienyl complex.