Categories: C=C Bond Formation >
Synthesis of allenes by rearrangement
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.
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.