Organic Letters
Letter
yield. (4) 1-(2,2-Dibromovinyl)benzene compound 1 with a
substituent at the ortho position on the phenyl ring (e.g., o-Me
and o-Cl) gave a trace amount of the corresponding product,
respectively. We reasoned that the ortho-substituent may block
the nucleophilic attack of the fluoride anion to the intermediate
6 in these cases (see Scheme 4). (5) (E)-(4,4-Dibromobuta-
1,3-dienyl)benzene 1n was also tested, and the corresponding
3n was obtained in a 30% yield (Scheme 2). (6) We found that
the Z/E ratio of 3a−n/3a′−n′ is in the range of 40/1−70/1,
which was determined by GC-MS. It is important to note that
the fluorinated styrene compounds are highly volatile for
isolation. As a result, we evaluated the efficiency of this reaction
based on both GC yield and isolated yield.
(Z)-1-(2-bromo-1-fluorovinyl)benzene compounds derived
from TBAF·3H2O.
ASSOCIATED CONTENT
* Supporting Information
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S
The Supporting Information is available free of charge on the
Details for experiments conditions, characterization data,
copies of 1H and 13NMR spectra for all isolated
Two control experiments were performed under the
optimized conditions: (i) (bromoethynyl)benzene 5a produced
3a (73%) along with 4a (25%) (eq 1), and (ii) (Z)-1-(2-
bromo-1-fluorovinyl)-4-chlorobenzene 3a was treated with
TBAF·3H2O 2e only giving 7% of 4a; 5a was not detected
by GC-MS analysis (eq 2, Scheme 3).
AUTHOR INFORMATION
Corresponding Author
■
Author Contributions
†M.Z. and L.M. contributed equally.
Notes
Scheme 3. Two Control Experiments
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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We thank the NSFC (No. 21272175) and Shanghai science and
technology commission (14DZ2261100) for generous financial
support.
REFERENCES
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On the basis of these control experiments and the previous
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Scheme 4. Possible Mechanism of the Present Reaction
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In one pot, the debromination reaction of 1-(2,2-
dibromovinyl)benzene compound 1 with TBAF·3H2O 2e in
toluene at 100 °C occurs to produce the (bromoethynyl)-
benzene19 5. The ionization of TBAF in H2O gives a fluoride
anion,12 which attacks the bromine atom on 5 to form an
ethynyl anion12 6 and BrF21 by a reversible process. Finally, an
addition reaction of 6 with BrF21 in the presence of H2O would
afford (Z)-1-(2-bromo-1-fluorovinyl)benzene product 3;22
meanwhile minor product 412,14 is released in the course of
the reaction.
In conclusion, we have developed a direct fluorination of 1-
(2,2-dibromovinyl)benzene compounds 1 with TBAF·3H2O
2e, which afforded (Z)-1-(2-bromo-1-fluorovinyl)benzene
compounds in good to high yields with excellent regioselectiv-
ities. This method allows the use of wet tetra-n-butyl-
ammonium fluoride as the fluorine source in the absence of a
transition metal. This is the first example of the synthesis of
C
Org. Lett. XXXX, XXX, XXX−XXX