A dirhodium(II)/phosphine catalyst with a chiral environment at the bridging site was developed for the asymmetric arylation of phenanthrene-9,10-diones with arylboronic acids. In contrast to the classic chiral bridging carboxylic acid (or derivatives) ligand strategy of bimetallic dirhodium(II) catalysis, in this reaction, tuning both axial and bridging ligands realized the first Rh 2 (OAc) 4 /phosphine-catalyzed highly enantioselective carbonyl addition reaction. The kinetic analysis reveals that dirhodium(II) and arylboronic acid follow the first-order kinetics, while phenanthrene-9,10-dione is zeroth-order. These data supported the proposed catalytic cycle, where the key intermediate in the rate-determining step involved the dirhodium(II) complex and arylboronic acid. Finally, axially chiral biaryls were prepared based on a newly developed oxidative ring-opening reaction of αhydroxyl ketones with a base and molecular oxygen, which featured a central-to-axial chirality transfer radical β-scission step.
An acid-mediated rapid synthesis
of α-aryl azahelicenes via
C–C bond cleavage of helical 9H-fluoren-9-ols
is reported. The newly introduced aryl ring and pyridine moieties
provide an excellent opportunity to further tune the properties of
azahelicences: i.e., photoluminescence. The novel α-aryl azahelicenes
showcase high circularly polarized luminescence (CPL) efficiencies
(4.5 × 10–3) as well as CPL brightness (B
CPL), reaching 7.39 M–1 cm–1, which indicates a potential application as chiral
emitters.
A palladium-catalyzed enantioselective ring-opening/carbonylation of cyclic diarylsulfonium salts is reported. In comparison to thioethers, the sulfonium salts displayed high reactivity and enabled the reaction being performed at mild conditions (room...
The front cover picture illustrates the palladium‐catalyzed the chirality transfer from peripheral stereogenic carbon center to axial chirality starting from 8H‐indenothiophen‐8‐ols. The process is different from traditional point‐to‐axial chirality transfer aromatization reaction of a non‐aromatic intermediate, in which the new created chiral axis is usually directly attach to a stereogenic centers. This reaction provides an easy way to access highly functionalized 3‐arylthiophene atropisomers in high enantioselectivity. Details can be found in the Update by Junwei Xi, Zhenhua Gu and co‐workers (L. Li, J. Xi, B. Hong, Z. Gu, Adv. Synth. Catal. 2023, 365, 594–599; DOI: 10.1002/adsc.202200957).
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