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Nucleophilic epoxidation is the formation of epoxides from electron-deficient double bonds through the action of nucleophilic oxidants. Nucleophilic epoxidation methods represent a viable alternative to electrophilic methods, many of which do not epoxidize electron-poor double bonds efficiently.〔Porter, M.; Skidmore, J. ''Org. React.'' 2009, ''74'', 425. 〕 Although the most commonly used asymmetric epoxidation methods (the Sharpless-Katsuki,〔Katsuki, T.; Martin, V. S. ''Org. React.'' 1996, ''48'', 1.〕 and Jacobsen〔Jacobsen, E. N.; Wu, M. H. In ''Comprehensive Asymmetric Catalysis''; Jacobsen, E. N., Pfaltz, A., Yamamoto, H., Eds.; Springer-Verlag: Berlin and Heidelberg, 1999; Vol. II, pp 649–678.〕 epoxidations) rely on the catalytic reactivity of electrophilic oxidants, nucleophilic oxygen sources substituted with a suitable leaving group can also act as epoxidation reagents. The classic example, the Weitz-Scheffer reaction〔Weitz, E.; Scheffer, A. ''Chem. Ber.'' 1921, ''54'', 2327.〕 employs hydrogen peroxide under basic conditions (Z = OH below). Other notable examples have employed hypochlorites (Z = Cl) and chiral peroxides (Z = OR *). ''(1)'' Asymmetric versions of the above reaction have taken advantage of a number of strategies for achieving asymmetric induction. The highest yielding and most enantioselective methods include: * Use of stoichiometric chiral oxidant〔Adam, W.; Rao, P. B.; Degen, H.-G.; Saha-Möller, C. R. ''J. Am. Chem. Soc.'' 2000, ''122'', 5654.〕 * Use of stoichiometric metal peroxides substituted with chiral ligands〔Enders, D.; Zhu, J. Q.; Raabe, G. ''Angew. Chem., Int. Ed. Engl.'' 1996, ''35'', 1725.〕 * Use of stoichiometric chiral base〔Genski, T.; Macdonald, G.; Wei, X.; Lewis, N.; Taylor, R. J. K. ''Synlett'' 1999, 795.〕 * Use of polypeptides〔Da, C. S.; Wei, J.; Dong, S. L.; Xin, Z. Q.; Liu, D. X.; Xu, Z. Q.; Wang, R. ''Synth. Commun.'' 2003, ''33'', 2787.〕 Although the mechanisms of each of these reactions differ somewhat, in each case the chiral catalyst or reagent must be involved in the (enantio ) determining conjugate addition step. ''Cis''-epoxides are difficult to access using nucleophilic epoxidation methods. Nearly all nucleophilic epoxidations of ''cis'' olefins afford ''trans'' epoxides. ==Mechanism and Stereochemistry== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「asymmetric nucleophilic epoxidation」の詳細全文を読む スポンサード リンク
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