DOI: 10.1002/chem.201402265
Communication
&
Synthetic Methods
Synthesis of Dibenzothiophenes by Pd-Catalyzed Dual CÀH
Activation from Diaryl Sulfides
Rui Che,[a] Zhiqing Wu,[a] Zhengkai Li,[a] Haifeng Xiang,[a] and Xiangge Zhou*[a, b]
zenes or 2-haloaryltriflates by using palladium-catalyzed CÀC
Abstract: Palladium-catalyzed dual CÀH functionalization
and CÀS bond formations was established (route e).[6] Further-
of diaryl sulfides to form dibenzothiophenes (DBTs) by oxi-
more, the synthetic method of unsymmetrical DBTs by acid-
dative dehydrogenative cyclization is reported. This proto-
mediated intramolecular cyclization of biaryl methyl sulfoxides
col afforded various DBTs in moderate to good yields with
with inorganic reagents, sulfuric acid, and potassium carbonate
tolerance of a wide variety of substrates. Benzo[1,2-b:4,5-
was also issued (route f).[7] However, most of these methods
b’]bis[b]benzothiophene was successfully synthesized by
are limited by their reliance on necessities of prefunctionalized
this method, which was used as an organic semiconductor
starting materials or multistep procedures, which are neither
for field-effect transistors.
atom-economical nor environmentally friendly.
Dibenzothiophenes (DBTs) are
usually key core motifs in many
important organic compounds
including pharmaceuticals, pho-
toactive compounds, dyes, liquid
crystals, and conducting poly-
mers.[1] A number of synthetic
methods have been established
in recent years. For example,
Zeller and co-workers synthe-
sized DBTs bearing dimethyl sub-
stituents by using diaryl sulfide
with iodine and light under a ni-
trogen atmosphere in 1975
(Scheme 1, route a).[2] FaÇanꢀs
and co-workers disclosed the
cyclization of diaryl thioether
through a benzyne intermediate
(route b).[3] McNab’s group devel-
Scheme 1. Strategies toward the synthesis of dibenzothiophenes.
oped a method by using flash
vacuum pyrolysis of aryl 2-allylthiobenzoates (route c).[4]
Almost at the same time, Knochel and co-workers reported the
successful synthesis of DBTs by a ring-closure procedure start-
ing from functionalized dithiocarbamates (route d).[5] More re-
cently, a three-step strategy starting from 1-bromo-2-iodoben-
On the other hand, transition-metal-catalyzed oxidative CÀ
H/CÀH coupling has emerged as a powerful method for the
construction of biaryl scaffolds.[8] Utilization of two CÀH bonds
as the coupling partners avoids the steps for installation of
pre-activated functional groups and minimizes waste. Over the
last few years, considerable efforts have been made to develop
catalytic intramolecular dehydrogenative CÀC couplings to
construct heterocycles, such as carbazoles,[9] dibenzofurans,[9b]
phenanthridinones,[10] fluorenes,[11] and fluorenones.[12] Howev-
er, few synthetic methods of sulfur-containing heterocycles
were reported by this strategy, which might be caused by the
deactivating effect of sulfur on transition-metal catalysts.[5] No-
tably, an interesting protocol for the highly regioselective syn-
thesis of polysubstituted DBTs through a palladium-catalyzed
cascade reaction by using sulfoxide as a new traceless direct-
ing group was demonstrated by the group of Antonchick very
[a] R. Che, Z. Wu, Dr. Z. Li, Dr. H. Xiang, Prof. Dr. X. Zhou
Institute of Homogeneous Catalysis
College of Chemistry, Sichuan University
Chengdu 610064 (P. R. China)
Fax: (+86)28-8541-2026
[b] Prof. Dr. X. Zhou
Key Laboratory of Organic Synthesis of Jiangsu Province
College of Chemistry, Chemical Engineering and Materials Science
Soochow University, Suzhou 215123 (P. R. China)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201402265.
Chem. Eur. J. 2014, 20, 1 – 5
1
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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