Highly Stereoselective Olefinating Reagents
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
- 1)Lewis base-catalyzed carbonyl olefination
- 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.
- b)A. J. Lovey, B. A. Pawson, J. Med. Chem. 1982, 25, 71.
The prices are subject to change without notice. Please confirm the newest price by our online catalog before placing an order.
In addition, sales products changes with areas. Please understand that a product is not available when the product details page is not displayed.
