Categories: C=C Bond Formation >
Synthesis of allenes by rearrangement
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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.
Triazole-Au (TA-Au) complexes are effective chemoselective catalysts in
promoting propargyl ester/ether 3,3-rearrangements. Unlike other reported Au
catalysts, TA-Au provided effective chirality transfer without racemization over
a long period of time, giving enantioenriched allenes with excellent
stereoselectivity in excellent yields.
D. Wang, L. N. S. Gautam, C. Bollinger, A. Harris, M. Li, X. Shi, Org. Lett., 2011,
13, 2618-2621.
A transition-metal-free intermolecular Claisen rearrangement
process enables to introduce allyl and allenyl groups into the α position of tertiary
amides in good yield under mild conditions. In this transformation, amides were activated by
trifluoromethanesulfonic anhydride to produce keteniminium ion intermediates
that exhibit strong electrophilic activity.
Z.-J. Niu, L.-H. Li, X.-S. Li, H.-C. Liu, W.-Y. Shi, Y.-M. Liang, Org. Lett., 2021, 23,
1315-1320.
Unprecedented decompositions of unprotected alkynyl hydrazones provide
allenoates via DABCO-promoted Wolff-Kishner reduction, tetrasubstituted
α,γ-dihaloallenoates in the presence of N-halosuccinimides, and
functionalized tricyclic azepines in the presence of DBU.
P. Jamwal, A. Sharma, R. Gurubrahamam, Org. Lett., 2023, 25,
6607-6612.
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.
Copper-Catalyzed Reductive Ireland-Claisen Rearrangements of Propargylic
Acrylates and Allylic Allenoates
S. Guo, K. C. Wong, S. Scheeff, Z. He, W. T. K. Chan, K.-H. Low, P. Chiu, J. Org. Chem., 2022, 87,
429-452.