N-Heterocyclic Carbene Catalyzed [4+2] Annulation of Enals via a Double Vinylogous Michael Addition: Asymmetric Synthesis of 3,5-Diaryl Cyclohexenones.
A strategy for the N-heterocyclic carbene (NHC) catalyzed asymmetric synthesis of 3,5-diaryl substituted cyclohexenones has been developed via oxidative [4+2] annulation of enals and alkenylisoxazoles. It is the first example of using NHC organocatalysis in a double vinylogous Michael type reaction, a challenging but highly desirable topic. This unprecedented protocol affords good yields as well as high to excellent diastereo- and enantioselectivities.
['Chen|Xiang-Yu|XY|', 'Liu|Qiang|Q|', 'Chauhan|Pankaj|P|', 'Li|Sun|S|', 'Peuronen|Anssi|A|', 'Rissanen|Kari|K|', 'Jafari|Ehsan|E|', 'Enders|Dieter|D|0000-0001-6956-7222']
N-heterocyclic carbenes annulations Michael addition asymmetric synthesis cyclohexenones