Angewandte
Chemie
DOI: 10.1002/anie.201201374
Synthetic Methods
Rhodium(II)-Catalyzed Cyclization of Bis(N-tosylhydrazone)s: An
Efficient Approach towards Polycyclic Aromatic Compounds**
Ying Xia, Zhenxing Liu, Qing Xiao, Peiyuan Qu, Rui Ge, Yan Zhang, and Jianbo Wang*
In memory of Howard E. Zimmerman
Polycyclic aromatic compounds (PACs), which include poly-
cyclic aromatic hydrocarbons (PAHs) and their heterocyclic
analogues, play important roles in various areas of organic
chemistry, medicinal chemistry, and material sciences.[1] Con-
sequently, the construction of such aromatic structures is of
great importance. In past decades enormous efforts have been
devoted to the development of efficient syntheses of PACs.[2]
Among the various methods, the construction of PACs
through the combination of cross-coupling reactions and
In the past decades, ring-closing metathesis (RCM) has
evolved into another highly efficient and versatile strategy for
[5]
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intramolecular C C bond formation. RCM has also been
applied to the construction of benzene rings in various
aromatic systems in recent years.[5e,g,6] In the RCM strategy,
the commonly used starting materials, 2,2’-dicarbonylbiaryl
derivatives, need to be first converted into the corresponding
2,2’-divinylbiaryl derivatives by the Wittig olefination
(Scheme 1, method B).[3c,6d,e,g,k] However, the Wittig olefina-
tion, although highly reliable, usually affords the divinyl
compounds in only moderate yields. Moreover, the divinyl
compounds in some cases are unstable, thus resulting in the
failure of Wittig/RCM process in PAC synthesis.[6e] In view of
the importance of the synthesis of PACs and the drawbacks of
the existing methods, we consider it highly desirable to
develop alternative and efficient process to access various
PACs.
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intramolecular C C bond formation is particularly attractive.
With such combinations, PACs can be rapidly accessed from
relatively simple aromatic substrates.[3] For the intramolecular
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C C bond formation the McMurry reaction is a powerful tool
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which can convert dicarbonyl functionality into C C bonds
(Scheme 1, method A).[4] However, in the McMurry reaction,
a stoichiometric amount of a reductive metal reagent is
required, and may result in moderate functional group
compatibility.
Diazo compounds are versatile substrates in organic
synthesis, particularly in transition-metal-catalyzed transfor-
mations.[7] The formation of C C bonds from diazo com-
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pounds in transition-metal-catalyzed process, the so-called
carbene dimer formation, has been well documented.[8–10]
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However, this type of C C bond formation has not attracted
much attention, presumably because of the following reasons:
1) diazo compounds, particularly bis(diazo) compounds, are
relatively unstable and not easily accessible; 2) the diverse
reaction pathways of carbene or metal carbenes make
carbene dimer formations undesired side-reactions in many
cases; 3) for the intermolecular dimerization of two different
carbenes, the selectivity is inevitably a grave problem.
Regardless of these challenges, significant progress has been
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Scheme 1. PAC synthesis through intramolecular C C bond formation.
Ts =4-toluenesulfonyl.
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made recently in the development of C C bond formation
based on carbene dimerization. Davies and co-workers have
realized the cross-coupling of two different diazo compounds
with rhodium(II) catalysts.[9e] Doyle and co-workers have
reported the construction of macrocycles through rho-
dium(II)-catalyzed reactions of bis(diazocarbonyl) com-
pounds.[10c] Che and co-workers developed a similar macro-
cycle synthesis based on their ruthenium(II) catalysts.[10d]
Recently, N-tosylhydrazones, which can be easily obtained
from the corresponding ketones or aldehydes, have been
extensively utilized as precursors of diazo compounds.[11–13]
Herein we report that the rhodium(II)-catalyzed intramolec-
ular cyclization of bis(N-tosylhydrazone)s is a highly efficient
[*] Y. Xia, Z. Liu, Q. Xiao, P. Qu, R. Ge, Dr. Y. Zhang, Prof. Dr. J. Wang
Beijing National Laboratory of Molecular Sciences (BNLMS) and
Key Laboratory of Bioorganic Chemistry and Molecular Engineering
of Ministry of Education, College of Chemistry
Peking University, Beijing 100871 (China)
E-mail: wangjb@pku.edu.cn
Prof. Dr. J. Wang
The State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences
354 Fenglin Lu, Shanghai 200032 (China)
[**] The project is supported by the National Basic Research Program of
China (973 Program, No. 2012CB821600), NSFC (Grant No.
21072009, 20902005, 20832002), and RFDP.
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process for converting dicarbonyl functionality into C C
bonds.[14] This transformation provides an alternative and
efficient strategy for PAC synthesis (Scheme 1, method C).
Supporting information for this article is available on the WWW
Angew. Chem. Int. Ed. 2012, 51, 1 – 5
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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