Chemical Science
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Journal Name
ARTICLE
This work was supported by a Grant-in-Aid for Scientific
obtain a high conversion. This requirement for a high catalyst
loading could be attributed to the reluctance of the product 2 to
dissociate from the Pd(II) center (i.e., 33→2). In fact, the addition of
2 to the palladium-catalyzed C-H/C-S coupling reaction led to a
DOI: 10.1039/C5SC04890G
Engineering, Osaka University, for their assistance with HRMS.
decrease in the yield of the cyclized product by 30%.19
A
characteristic feature of the mechanism of the C-H/C-S coupling is
that the product is released by an oxidative addition step (31→32),
which occurs after the reductive elimination step (30→31), and
allows for the regeneration of the Pd(II) species without the addition
of an external oxidant. This mechanistic scenario is therefore
unusual compared with the most common Pd(II)-catalyzed processes,
which typically end up with a product-forming reductive elimination
step to generate a Pd(0) species and consequently require an external
oxidant to regenerate Pd(II).20
Notes and references
a
Department of Applied Chemistry, Faculty of Engineering, Osaka
University,
Suita,
Osaka
565-0871,
Japan.
E-mail:
tobisu@chem.eng.osaka-u.ac.jp; chatani@chem.eng.osaka-u.ac.jp
b
Center for Atomic and Molecular Technologies, Graduate School of
Engineering, Osaka University, Suita, Osaka 565-0871, Japan
†
Electronic Supplementary Information (ESI) available: Experimental
procedures and characterization data for all new compounds. See
DOI: 10.1039/b000000x/
1
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Scheme 4 Possible mechanism
Conclusions
In summary, we have developed a new C-H/C-S coupling strategy
for the catalytic synthesis of dibenzothiophene derivatives. In
contrast to previously reported methods for the synthesis of
benzothiophene derivatives via C-H functionalization, our newly
developed method does not require reactive functionalities such as
Ar-X or S-H, or the addition of an external stoichiometric oxidant.
This C-H/C-S coupling procedure is characterized by its unique
mechanism, with the product being formed by an oxidative addition
step, rather than a reductive elimination. Further studies towards the
application of this mechanistic feature to the synthesis of other
heterocycles are currently underway in our laboratories.
5
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An elegant catalytic synthesis of dibenzo[b,d]thiophene-1-
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Acknowledgments
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