Iridium-Catalyzed Asymmetric Hydroalkenylation of Norbornene Derivatives

Abstract

Transition-metal-catalyzed asymmetric hydroalkenylation of alkenes provides an atom-economical method to build molecular complexity from easily available materials. Herein we report an iridium-catalyzed asymmetric hydroalkenylation of unconjugated alkenes with acrylamides and acrylates. The catalytic hydroalkenylation of norbornene derivatives occurred to form products with allylic stereocenters with high chemo-, regio-, and stereoselectivities. DFT calculations revealed that the migratory insertion is irreversible and the enantiodetermination step. Communication pubs.acs.org/Organometallics

Our Voyage from Catalytic Cross-Hydroalkenylation to Transfer-Dehydroaromatization of Cyclic π-Systems: Reactivity and Selectivity Changes Enabled by NHC-Ni and NHC-Pd Hydride Equivalents

“…exo-2-Alkenylnorbornanes were obtained from catalytic cross-hydroalkenylation of norbornenes with ethylene or ,-unsaturated carbonyls (like esters and amides) by using Ni, 31a,34 Ru, 35 or Ir (Scheme 4). 36 In the pioneering examples, the chemoselectivity and regioselectivity were controlled by distinct factors: (a) ringstrain relief after hydrometallation; (b) a polarized olefin that can facilitate the desired metallacycle formation with a reactive -CH for elimination; (c) alkenyl C-H activation and coordination of the carbonyl group to metal. These approaches effectively limited the problems related to the Scheme 3 NHC effects on catalytic regiodivergent cross-hydroalkenylation…”

Iridium-Catalyzed Branch-Selective and Enantioselective Hydroalkenylation of α-Olefins through C–H Cleavage of Enamides

“…The pioneering early work of Murai on linear-selective hydroarylation and Ellman and Bergman on enantioselective intramolecular cyclization have laid the foundation for this approach . Since then, significant advances have been made, in terms of both intramolecular and intermolecular enantioselective variants. − …”

“…Despite the progress made in this field of enantioselective alkene hydrocarbofunctionalization during the past decades, one prominent limitation is the scope of the alkenes. Currently, the alkenes are largely restricted to strained alkenes, conjugated alkenes, or functionalized alkenes. , Catalytic enantioselective intermolecular hydroarylation and hydroalkenylation of minimally polarized, unactivated α-olefins remains a long-standing challenge, due to the low reactivity of α-olefins and the formation of the usually favored linear product. − Such examples are extremely scarce. Recently, a few catalytic systems have begun to emerge in this direction (Scheme A).…”