Please cite this article in press as: Chen et al., Selective C-C Bond Scission of Ketones via Visible-Light-Mediated Cerium Catalysis, Chem (2019),
Article
Selective C-C Bond Scission of Ketones
via Visible-Light-Mediated
Cerium Catalysis
Yilin Chen,1,3 Jianbo Du,1,3 and Zhiwei Zuo1,2,4,
SUMMARY
The Bigger Picture
In the endeavor to search for
innovative catalysis, the synthetic
chemists face ever-increasing
financial and environmental
demands in chemical production.
The development of catalytic
modes employing abundant and
inexpensive metal catalysts has
drawn significant research
Here, we report a general catalytic manifold for the selective C–C bond scission
of ketones via the exploitation of the ligand-to-metal charge transfer (LMCT)
excitation mode. Through a cooperative utilization of Lewis acid catalysis and
LMCT catalysis, the C–C bond of ketones could be selectively and effectively
cleaved, enabling the installation of different functionalities at each carbon of
the cleaved C–C bond through a sequential and orthogonal manner. This reac-
tion manifold serves as a photocatalytic alternative to the Norrish type I reaction
with the combination of visible light and inexpensive cerium salts. Under oper-
ationally simple conditions, a wide range of acyclic and cyclic ketones, from
simple strained cyclobutanones to complex androsterone with less strained cy-
clopentanone moiety, could be successfully transformed into versatile chemical
building blocks.
attention in the chemical
community with regard to
addressing the current challenges
in the sustainable development of
chemical synthesis. The selective
C–C bond cleavage and
INTRODUCTION
The selective cleavage of C–C bonds, as counterproductive as it seems to have
disassembled the critical component of organic molecule frameworks, provides
intriguing opportunities to streamline complex molecule synthesis significantly.1–3
The utilization of ubiquitous and robust C–C bonds as functional handles could
enable unconventional and efficient installations of multiple functionalities concur-
rently4,5 and, more importantly, offers unique opportunities to rapid complexity
generation via skeletal reconstruction.6–8 Given that ketones are commonly occur-
ring functionalities in a wide range of easily accessible starting materials and com-
plex natural products, the cleavage and functionalization of C–C bonds in ketones
has become an emerging area for the development of novel transformations.
Eminently, elegant catalytic systems employing transition metals (e.g., Rh, Ir),
have enabled a variety of synthetically valuable transformations with the advance-
ment of transition metal catalysis.8–17 Although activation strategies including
strain release, aromatization, and chelation-assistance have been successfully em-
ployed to override the thermodynamic and kinetic barriers of C–C bonds in various
types of molecules, they have also imposed some limitations on the generality and
scope of those catalytic transformations. Meanwhile, the ever-increasing financial
and environmental demands in chemical production have spurred significant
research attention in the sustainable development of low-cost and abundant metal
catalysts.18–21 To further expedite the application of C–C bond cleavage transfor-
mation in chemical synthesis, the development of general and efficient catalytic
paradigms utilizing inexpensive and sustainable metal catalysts remains in high de-
mand. Herein, we report a practical and economic catalytic system, through the
cooperative utilization of abundant cerium and titanium catalysts, for the selective
functionalizations have recently
emerged as an unconventional yet
advantageous synthetic strategy,
nevertheless, currently
predominated by transition
metals such as Rh, Ir, etc. The
utilization of cost-effective and
abundant metal catalysts would
undoubtedly expedite the
synthetic application of C–C bond
cleavage transformations while
addressing economic and
ecological concerns; more
importantly, the use of metal
catalysts would potentially
prompt the development of new
catalytic paradigms.
Chem 6, 1–14, January 9, 2020 ª 2019 Elsevier Inc.
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