The
visible-light-driven, phase-transfer-catalyzed, enantioselective
perfluoroalkylation and trifluoromethylation of cyclic β-ketoesters
is described. The photo-organocatalytic process, which occurs at ambient
temperature and under visible light illumination, is triggered by
the photochemical activity of in situ-generated electron
donor–acceptor complexes, arising from the association of chiral
enolates and perfluoroalkyl iodides. Preliminary mechanistic studies
are reported.
An enantioselective C-H arylation of phosphine oxides with o-quinone diazides catalyzed by an iridium(III) complex bearing an atropchiral cyclopentadienyl (Cp ) ligand and phthaloyl tert-leucine as co-catalyst is reported. The method allows access to a) P-chiral biaryl phosphine oxides, b) atropo-enantioselective construction of sterically demanding biaryl backbones, and also c) selective assembly of axial and P-chiral compounds in excellent yields and diastereo- and enantioselectivities. Enantiospecific reductions provide monodentate chiral phosphorus(III) compounds having structures and biaryl backbones with proven importance as ligands in asymmetric catalysis.
The
development of catalytic enantioselective transformations,
enabling the construction of complex molecular scaffolds from simple
precursors, has been a long-standing challenge in organic synthesis.
Recent achievements in transition-metal catalyzed enantioselective
functionalizations of carbon–hydrogen (C–H) bonds represent
a promising pathway toward this goal. Over the last two decades, iridium
catalysis has evolved as a valuable tool enabling the stereocontrolled
synthesis of chiral molecules via C–H activation. The development
of iridium-based systems with various chiral ligand classes, as well
as studies of their reaction mechanisms, has resulted in dynamic progress
in this area. This review aims to present a comprehensive picture
of the enantioselective functionalizations of C–H bonds by
chiral iridium complexes with emphasis on the mechanisms of the C–H
activation step.
Reported herein is a photochemical cascade process that combines the excited‐state and ground‐state reactivity of chiral organocatalytic intermediates. This strategy directly converts racemic cyclopropanols and α,β‐unsaturated aldehydes into stereochemically dense cyclopentanols with exquisite stereoselectivity. Mechanistic investigations have enabled elucidating the origin of the stereoconvergence, which is governed by a kinetic resolution process.
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