Hoppe

The first practical method for asymmetric epoxidation of primary and secondary allylic alcohols was developed by K.B. Sharpless in 1980 (T. Katsuki, 1980 K.B. Sharpless, 1983 A, B, 1986 see also D. Hoppe, 1982). Tartaric esters, e.g., DET and DIPT" ( = diethyl and diisopropyl ( + )- or (— )-tartrates), are applied as chiral auxiliaries, titanium tetrakis(2-pro-panolate) as a catalyst and tert-butyl hydroperoxide (= TBHP, Bu OOH) as the oxidant. If the reaction mixture is kept absolutely dry, catalytic amounts of the dialkyl tartrate-titanium(IV) complex are suflicient, which largely facilitates work-up procedures (Y. Gao, 1987). Depending on the tartrate enantiomer used, either one of the 2,3-epoxy alcohols may be obtained with high enantioselectivity. The titanium probably binds to the diol grouping of one tartrate molecule and to the hydroxy groups of the bulky hydroperoxide and of the allylic alcohol... 

H. Fischei and K. Hede, Hoppe-Zejkrs Z. PhjsioL Chem. 251, 85 (1938). 

R. Kuhn and P. Boulanger, Hoppe-Sejler s Z. Physiol Chem. 241, 233 (1936). 

A. Windaus and F. Bock, Z. Physiol Chem. Hoppe-Seglers 245, 168 (1937). 

E. Wiinsch, L. Moroder, R. Nyfeier, and E. Jager, Hoppe-Seyler s Z. Physiol. Chem.,... 

M 5000—10,000 polymer Purified by chromatography on Dowex 50 and/or by filtration through alumina before use [Frank Hoppe-Seyler s Z Physiol Chem.ie 360 991 1979], Hygroscopic, sol in H2O is 10%. 

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