Categories: C=C Bond Formation >
Synthesis of allenes
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Recent Literature
A selective copper-catalyzed hydride addition to propargylic chlorides
enables a mild and efficient synthesis of allenes from propargylic chlorides in
the presence of diisobutylaluminum hydride. This transformation provides a wide
range of functionalized allenes in good to excellent yields with high regio- and
stereoselectivities.
Y. Kim, H. Lee, H. Lee, Org. Lett.,
2018, 20, 5478-5481.
Various propargylic amines underwent a palladium-catalyzed hydrogen-transfer
reaction in the presence of (C6F5)3P,
giving the corresponding allenes in good yields.
H. Nakamura, T. Kamakura, M. Ishikura, J.-F. Biellmann, J. Am. Chem. Soc.,
2004, 126, 5958-5959.
Benzyl propargyl ethers react with a gold(I) catalyst to furnish substituted
allenes via a 1,5-hydride shift/fragmentation sequence. This transformation is
rapid and practical and can be performed under very mild conditions using
terminal as well as substituted alkyne substrates bearing a primary, secondary,
or tertiary benzyl ether group.
B. Bolte, Y. Odabachian, F. Gagosz, J. Am. Chem. Soc., 2010,
132, 7294-7296.
B. Bolte, Y. Odabachian, F. Gagosz, J. Am. Chem. Soc., 2010,
132, 7294-7296.
A metal-free, one-pot synthesis of substituted allenes from enones via the
corresponding α,β-unsaturated tosylhydrazones proceeds readily with high
compatibility of sensitive functional groups using a tertiary amine as a base.
This synthetic protocol provides synthetically important allenes without the use
of metallic reagents or catalysts.
M. Tang, C.-A. Fan, F.-M. Zhang, Y.-Q. Tu, W.-X. Zhang, A.-X. Wang, Org. Lett., 2008,
10, 5585-5588.
A copper hydride-catalyzed SN2′-reduction of propargylic carbonates
provides functionalized allenes in good yields. The method takes advantage of
the stabilizing effect of NHC ligands on CuH and offers high reactivity,
stereoselectivity, and functional group tolerance.
C. Deutsch, B. H. Lipshutz, N. Krause, Org. Lett., 2009,
11, 5010-5012.
The β-alkoxide elimination reaction of aryl- or alkyl-subsituted propargylic ethers with Negishi reagent
leads to allenes after hydrolysis, whereas TMS-substituted substrates afford
alkynes. Subsequent coupling
reactions of the zirconium intermediates with aryl iodides
in the presence of Pd(PPh3)4/CuCl provide a straightforward route for the
synthesis of multisubstituted allenes.
H. Zhang, X. Fu, J. Chen, E. Wang, Y. Liu, X. Li, J. Org. Chem., 2009,
74, 9351-9358.
1,1-diarylpropadienes and
1,3-diarylpropynes can be prepared by the sequential lithiation of
1-aryl-1-propynes, transmetalation, and the corresponding Pd(0)-catalyzed
cross-coupling with aryl halides.
S. Ma, Q. He, X. Zhang, J. Org. Chem., 2005, 70, 3336-3338.
The Au-catalyzed hydrative rearrangement of 1,1-diethynylcarbinol acetates in
wet CH2Cl2 produces either
5-acetoxy-2-alkyl-2-cyclopentenones or acetoxymethyl α-alkylallenones as a major
product depending on the temperature, reaction time, and catalyst loading.
C. H. Oh, S. Karmakar, J. Org. Chem., 2009,
74, 370-374.