Categories: C-C Bond Formation > Carbocyclic compounds > Cycloalkenes
Synthesis of cyclopropenes
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Recent Literature
A novel Rh(II)-catalyzed enantioselective [2 + 1]-cycloaddition of ethyl
diazoacetate to terminal acetylenes and olefins with high enantioselectivity is
described. The catalyst, which is readily available, robust, and effective, can
be recovered and reused.
Y. Lou, M. Horikawa, R. A. Kloster, N. A. Hawryluk, E. J. Corey, J. Am. Chem.
Soc., 2004, 126, 8916-8918.
Silver triflate is an efficient catalyst for the cyclopropenation of internal
alkynes using donor-/acceptor-substituted diazo compounds as carbenoid
precursors to yield highly substituted cyclopropenes, which cannot be
synthesized directly via rhodium(II)-catalyzed carbenoid chemistry.
J. F. Briones, H. M. L. Davies, Org. Lett., 2011,
13, 3984-3987.
Dianions generated from alkyllithium reagents and cycloprop-2-ene carboxylic
acids can be functionalized by electrophiles at the vinylic position. Due to
reproducibility issues for reactions that were carried out in Et2O, a
detailed study revealed that THF was a superior solvent. Additionally, it was
found that the addition of NMO has a beneficial effect both on the stability of
the dianions and on the rates of alkylation.
L. A. Fisher, J. M. Fox, J. Org. Chem., 2008,
73, 8474-8478.
A new cyclopropenation reaction, which involves Cα-Si bond insertion of
alkylidene carbenes derived from α-silyl ketones, features excellent selectivity
for insertion into Cα-Si bonds rather than insertion into Cγ-H bonds or addition
to γ,δ-double or -triple bonds. The selectivity trend clearly indicates that the
α-oxygen in the tether significantly promotes Cγ-H insertion.
J. Li, C. Sun, D. Lee, J. Am. Chem. Soc., 2010,
132, 6640-6641.
Sodium bromodifluoroacetate (BrCF2CO2Na) is an effective
difluorocarbene source for high-yielding synthesis of gem-difluorocyclopropanes
and gem-difluorocyclopropenes under mild conditions.
K. Oshiro, Y. Morimoto, H. Amii, Synthesis, 2010,
2080-2084.
The application of continuous flow technology enabled a controlled generation of
difluorocarbene from TMSCF3 and a catalytic quantity of NaI. The in
situ generated electrophilic carbene reacts smoothly with a broad range of
alkenes and alkynes to provide the corresponding difluorocyclopropanes and
difluorocyclopropenes within 10 min residence time at high reaction
concentrations.
P. Rullière, P. Cyr, A. B. Charette, Org. Lett., 2016, 18,
1988-1991.