Asymmetric Pummerer

G. Asymmetric Pummerer Rearrangement Induced by Ethoxy Vmyl Esters. . . 236... 

Asymmetric Pummerer rearrangement is a very attractive reaction as previously described. In particular, the reactions induced by SKA work well, and may be synthetically exploited in many cases. The results described here demonstrate that the stereoselective a-deprotonation of the sulfoxide is a prerequisite process for asymmetric induction in the Pummerer reaction. Since many kinds of synthetic and enzymatic preparative methods of optically pure sulfoxides have been developed, the present Pummerer-type reaction will be applicable to many other chiral sulfoxides with one a-substituent, chiral vinylsulfoxides and chiral co-carbamoylsulfox-ides, thus leading to enantioselective syntheses of many new bioactive compounds in the near future. 

Kita, Y., Shibata, N. Asymmetric Pummerer-type reactions induced by 0-silylated ketene acetals. Synlett 1996, 289-296. 

Kita, Y., Shibata, N., Yoshida, N., Fujita, S. First highly asymmetric Pummerer-type reaction in chiral, non-racemic acyclic sulfoxides induced by 0-silylated ketene acetal. J. Chem. Soc., Perkin Trans. 1 1994, 3335-3341. 

Shibata, N., Matsugi, M., Kawano, N., Fukui, S., Fujimori, C., Gotanda, K., Murata, K., Kita, Y. Highly asymmetric Pummerer-type reaction induced by ethoxyvinyl esters. Tetrahedron Asymmetry 997, 8, 303-310. 

Ruano, J. L. G., Paredes, C. G. Intramolecular asymmetric Pummerer reactions as a key step in the synthesis of bicyclic precursors of anthracyclinones. Tetrahedron Lett. 1999,41,261-265. 

Asymmetric Pummerer reactions with chiral sulfinates have been moderately successful but avoid pathway A, or more specifically, an achiral thionium ion, although... 

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