Organic & Biomolecular Chemistry
Communication
Summing up the observations made during the investi-
gations of the scope, it becomes obvious that the nature of the
employed terminal alkyne plays an important role (which
supports the crucial role of the intermediate Li-acetylide). Thus
this reaction works best for more electron-neutral terminal
alkynes, while the presence of more polar groups or silyl groups
unfortunately reduces the reactivity and increasing amounts of
homocoupling products are observed in those cases.
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In conclusion, we have found that dissymmetric 1,3-diynes
3 can be synthesized without the need of any (transition
metal) catalysts by reacting terminal alkynes 1 (which are
in situ deprotonated with n-BuLi) with hypervalent iodine-
based electrophilic alkyne-transfer reagents 2. This procedure
works in reasonable yields for different terminal alkynes 1 as
well as iodine reagents 2 and thus may provide a complemen-
tary protocol to the recently developed powerful gold-catalysed
approaches.7
General reaction procedure: 140 µL (0.22 mmol, 1.1 eq.) of a
solution of n-BuLi (1.6 M in hexane) were added to a solution
of the corresponding terminal alkyne 1 (0.20 mmol, 1.0 eq.) in
dry THF (1 mL) at −78 °C. After stirring for 2 h, the corres-
ponding ethynyl-benziodoxolone 2 (0.30 mmol, 1.5 eq.) was
added in one portion. The mixture was allowed to reach room
temperature over 3 h while stirring rapidly. The resulting
suspension was quenched with 2 mL of a saturated solution of
NaHCO3 and extracted three times with 5 mL dichloro-
methane. After evaporation of the solvent, the crude product
was purified by column chromatography (silica gel) to afford
the targeted diyne 3 in the reported yield.
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Conflicts of interest
There are no conflicts to declare.
Acknowledgements
The NMR spectrometers used were acquired in collaboration
with the University of South Bohemia (CZ) with financial support
from the European Union through the EFRE INTERREG IV
ETC-AT-CZ program (project M00146, “RERI-uasb”).
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2017, 56, 6994–6998; (b) S. Banerjee and N. T. Patil, Chem.
Commun., 2017, 53, 7937–7940.
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Notes and references
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