Organic Letters
Letter
functional materials as well as testing bioactivity of some
compounds.
Scheme 3. Preliminary Mechanistic Studies
ASSOCIATED CONTENT
* Supporting Information
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S
Experimental procedures, analytical data for all compounds, and
crystallographic data (CIF). This material is available free of
AUTHOR INFORMATION
Corresponding Authors
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we investigated the reactivity of thiophene 4, which might be
formed from 1a under base.13d Indeed, upon reaction with
ethyl 2-cyanoacetate, 4 was also converted to give benzo[b]-
thiophene 2a in 76% yield (Scheme 3b). This result suggested
that benzo[b]thiophene construction might go through the
thienannulation/benzannulation sequence in this reaction.
Although the precise reaction mechanism cannot be definit-
ively established at the current stage, on the basis of the above
results and previous reports,13a,d a plausible mechanism was
proposed in Scheme 4. Initially, deprotonation at one of the
Author Contributions
†W.M. and X.L. contributed equally.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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Financial support from the National Natural Science
Foundation of China (No. 21202017) is greatly appreciated.
Scheme 4. Putative Reaction Mechanism
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ring-opening reaction to generate the thiolate anion II,13d
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sequential intramolecular heteroannulation16 and protonation.
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Org. Lett. 2015, 17, 1746−1749