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Synfacts 2007(4): 0403-0403  
DOI: 10.1055/s-2007-968337
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Iron(III)-Catalyzed Enantioselective Synthesis of Allenes

Contributor(s): Mark Lautens, Praew Thansandote
C.-Y. Li, X.-B. Wang, X.-L. Sun, Y. Tang*, J.-C. Zheng, Z.-H. Xu, Y.-G. Zhou*, L.-X. Dai
Shanghai Institute of Organic Chemistry and Dalian Institute of Chemical Physics, P. R. of China
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Publikationsdatum:
23. März 2007 (online)

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Significance

Olefination of ketenes with ethyl diazoacetate using an Fe(III) catalyst and triphenyl­phosphine provides an efficient synthesis of 4-mono­substituted and 4,4-disubstituted allenic esters. Only 0.5 mol% of Fe(TCP)Cl is required and the reaction conditions are mild. The phosphine ligand can also be recovered and reused. The scope of the reaction is broad and encompasses a variety of substituents on the ketene, including H, Br, alkyl and aryl groups. A one-pot strategy has also been developed for unstable ketenes by synthesizing the ketene in situ. An asymmetric version is possible by using a chiral phosphine ligand, and affords chiral allenes in good yields and excellent enantioselectivities.