Helicene‐Based Phosphite Ligands in Asymmetric Transition‐Metal Catalysis: Exploring Rh‐Catalyzed Hydroformylation and Ir‐Catalyzed Allylic Amination

Abstract

Starting from the optically pure [6]helicene-like alcohol (P,3S)-3-methyl-4-(4-methylphenyl)-1, 3,6,7-tetrahydrobenzo-[c]benzo [5,6]phenanthro [4,3-e]oxepin-14-ol, four helical phosphites were prepared from the corresponding chlorophosphites. These ligands containing parent or substituted 1,3,2-dioxaphospholan-2-yl or dibenzo [d,f][1,3,2]dioxaphosphepin-6-yl moieties were applied to the asymmetric hydroformylation of terminal alkenes catalyzed by Rh(acac)(CO) 2 and the asymmetric allylic amination of cinnamyl-type carbonates catalyzed by [Ir(cod)Cl] 2 . The helical phosphite containing the dibenzo [d,f][1,3,2]dioxaphosphepin-6-yl group was most successful in the asymmetric hydroformylation of

Rational Design and Synthesis of [5]Helicene-Derived Phosphine Ligands and Their Application in Pd-Catalyzed Asymmetric Reactions

“…Thus, helicenes can be utilized them a broad range of applications in chiral materials, in the chiral recognition of biomolecules, and in asymmetric synthesis161718192021222324. More specifically, chiral helicene-based trivalent phosphorus ligands are efficient asymmetric inductors in metal-catalyzed asymmetric reactions and show good to excellent enantioselectivities252627282930313233. We hypothesized that novel helicenylphosphine ligands, which induce intramolecular metal-arene interactions, could be used to construct an efficient chiral catalytic system.…”

Phosphathiahelicenes: Synthesis and Uses in Enantioselective Gold Catalysis

“…However, both the synthesis of helical phosphorus ligands2 and their uses in enantioselective organometallic catalysis have been underdeveloped so far. Catalytic screenings in enantioselective reactions mainly include Rh‐promoted hydrogenations or hydroformylations of olefins,2e, 3 palladium‐promoted allylic substitutions4 and Ir‐promoted allylic aminations of cinnamyl‐type substrates 3c. The phosphines used in these processes display phosphorus functions grafted on helical scaffolds.…”

Helical Phosphorus Derivatives

“…In 2011, Eilbracht, Star a, Starý, and coworkers developed a nonphotochemical strategy allowing a scalable and resolution-free access to a new class of enantioenriched [6]-heterohelicene-based phosphite ligands (þ)-(P,S)-33e36 (Scheme 11) (11EJO3849). The key feature of this attractive method …”

“…In this transformation, the solvent (dichloromethane) in combination with the Ir(I)/(þ)-(P,S)-33 catalyst, prepared in situ from [Ir(COD)Cl] 2 and the (þ)-(P,S)-33 ligand bearing the pinacol unit, was decisive for achieving high catalytic activity. Under optimized reaction conditions, various allyl carbonates were efficiently converted to the corresponding allylic amines 39aed in good yields (60e95%), with excellent enantioselectivities ranging up to 90%, and high regioselectivity in favor of the branched products (11EJO3849).…”