Categories: C-C Bond Formation > Chains >
Synthesis of substituted allenes
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Recent Literature
The palladium-catalyzed of triorganoindium reagents to propargylic esters
afforded via an SN2' rearrangement allenes in good yields and with high
regioselectivity. The reaction of chiral, nonracemic propargylic esters
takes place with high anti-stereoselectivity providing allenes with
high enantiomeric excess.
R. Riveiros, D. Rodríguez, J. P. Sestelo, L. A. Sarandeses, Org. Lett.,
2006,
8, 1403-1406.
The SN2′ reaction of propragyl mesylates with organozinc reagents was
dramatically improved in DMSO as solvent, and the conversion of a chiral
substrate was successfully achieved without loss of optical purity using a
LiCl-free diorganozinc reagent.
K. Kobayashi, H. Naka, A. E. H. Wheatley, Y. Kondo, Org. Lett.,
2008,
10, 3375-3377.
An efficient synthetic method provides tri- and tetra-substituted allenes by the
reaction of allylindium reagents with 3°-propargyl alcohols. Allylindium
reagents are generated in situ from indium and allyl bromides.
K. Lee, P. H. Lee, Org. Lett., 2008,
10, 2441-2444.
Lithiation of 1-aryl-3-alkylpropadienes and subsequent transmetalation with zinc
bromide followed by Pd-catalyzed Negishi coupling reactions with halides
afforded the corresponding trisubstituted allenes in a highly regioselective
fashion with good yields. A plausible regioselective lithiation mechanism was
proposed on the basis of deuterium labeling experiments.
J. Zhao, Y. Liu, S. Ma, Org. Lett., 2008,
10, 1521-1523.
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.
Tertiary homopropargyl alcohols can be used as allenylmetal equivalents in a
palladium-catalyzed reaction with aryl halides to provide arylallenes
regioselectively. The reaction includes retro-propargylation, which proceeds in
a concerted fashion via a cyclic transition state and transfers the
stereochemistry of homopropargyl alcohols through C-C bond cleavage.
S. Hayashi, K. Hirano, H. Yorimitsu, K. Oshima, J. Am. Chem. Soc., 2008,
130, 5048-5049.
Reactions of various carbonyl compounds with organoindium reagent in situ
generated from indium and 1-bromopent-4-en-2-yne derivatives gives
functionalized vinyl allenols in good yields. Treatment of vinyl allenols with
gold catalyst, dienophile, or indium trihalide produced functionalized
dihydrofuran, cyclohexene, or 2-halo-1,3-diene derivatives in very good yields.
J. Park, S. Hong, P. H. Lee, Org. Lett.,
2008,
10, 5067-5070.
A AuCl-catalyzed, flexible synthesis of highly substituted, benzyl-protected
phenols unites enal/enones and benzyl allenyl ethers in a [3+3] fashion in two
steps, allowing excellent control of substitution at the benzene ring.
X. Huang, L. Zhang, Org. Lett., 2007,
9, 4627-4630.
Arynes, generated in situ from ortho-silylaryl triflates, undergo ene
reaction with alkynes possessing propargylic hydrogen in the presence of
KF/18-crown-6 in THF at room temperature to give substituted phenylallenes
in good to moderate yields.
T. T. Jayanth, M. Jeganmohan, M.-J. Cheng, S.-Y. Chu, C.-H. Cheng, J. Am.
Chem. Soc.,
2006,
128, 2232-2233.
Various arylallenes and alkenylallenes were prepared via coupling of
allenylstannanes with aryl iodides or alkenyl iodides in the presence of Pd(PPh3)4
as catalyst, LiCl, and DMF as solvent.
C.-W. Huang, M. Shanmugasundaram, H.-M. Chang, C.-H. Cheng,
Tetrahedron, 2003, 59, 3635-3641.
Enantioenriched propargyl mesylates or perfluorobenzoates react with α-(N-carbamoyl)alkylcuprates
to afford scalemic α-(N-carbamoyl) allenes. Subsequent N-Boc
deprotection and AgNO3-promoted cyclization afford enantioenriched
N-alkyl-3-pyrrolines.
R. K. Dieter, N. Chen, V. K. Gore, J. Org. Chem., 2006,
71, 8755-8760.
Homoallenic alcohols are prepared from various propargyl vinyl ethers using a
trinuclear gold(I)-oxo complex, [(Ph3PAu)3O]BF4,
as a catalyst for propargyl Claisen rearrangement at room temperature.
B. D. Sherry, F. D. Toste, J. Am. Chem. Soc.,
2004,
126, 15978-15979.
Various arylallenes and alkenylallenes were prepared via coupling of
allenylstannanes with aryl iodides or alkenyl iodides in the presence of Pd(PPh3)4
as catalyst, LiCl, and DMF as solvent.
C.-W. Huang, M. Shanmugasundaram, H.-M. Chang, C.-H. Cheng, Tetrahedron,
2003, 59, 3635-3641.
