| T2592 | Trimethylsilylketene Ethyl Trimethylsilyl Acetal (mixture of isomer) (1) |
5g |
| F0692 | Fluorotrimethylsilylketene Ethyl Trimethylsilyl Acetal (mixture of isomer) (2) |
5g |
Mukaiyama and Michida have reported that E/Z mixtures of ketene acetals 1 and 2 react with various kinds of aldehydes in the presence of a catalytic amount of acetate salts to give α,β-unsaturated esters in high yields with excellent stereoselectivities.1) This procedure has some advantages over conventional methods such as the Peterson reaction and the Horner-Wadsworth-Emmons (HWE) reaction. For example:
1) Catalytic reaction (with no need of equimolar amount of base); 2) Co-product (TMS2O) can be removed easily by evaporation; 3) High stereoselectivity is obtained by the proper choice of the counter cation of the catalyst.
It is notable that Z-isomers are obtained with excellent stereoselectivity by using 2 in the synthesis of α-fluoro-α,β-unsaturated esters. On the other hand, E-isomers are the major products in the case of the fluorinated-HWE reagent.2) Therefore, the complementary use for the stereoselective synthesis of α-fluoro-α,β-unsaturated esters has been realized.
References
a) M. Michida, T. Mukaiyama, Chem. Lett. 2008, 37, 704[DOI]. b) M. Michida, T. Mukaiyama, Chem. Lett. 2008, 37, 890[DOI].
2) Synthesis of (E)-α-fluoro-α,β-unsaturated ester
a) R. S. H. Liu, H. Matsumoto, A. E. Asato, M. Denny, Y. Shichida, T. Yoshizawa, F. W. Dahlquist, J. Am. Chem. Soc. 1981, 103, 7195[DOI]. b) A. J. Lovey, B. A. Pawson, J. Med. Chem. 1982, 25, 71[DOI].
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