Group 5 metal-promoted oxidations epoxidations using vanadyl acetylacetonate

Group 5 metal-promoted oxidations epoxidations using vanadyl acetylacetonate 

Although it is added to the reaction mixture, V(=0)(acac)2 is not the actual catalyst in these reactions. The acetylacetone ligands are degraded to formic and acetic acid and V(=0)(0R)3 species quickly form. The acidic byproducts can cause problems in reactions leading to acid-sensitive epoxides. In these cases it is better to use isolated trialkyl vanadates as catalysts. The species V(—0)(0R)3 (R = Et, Pr, Pr ) work best. 

CautionI Employ the standard precautions outlined in the introduction to this chapter for this reaction. Strong acids, transition metal salts, or metal syringe needles should never be added to concentrated Bu OOH stock solutions. Aliquots of Bu OOH remaining after use in reactions should not be returned to stock - solutions. 1,2-Dichloroethane should not be used as a solvent with Bu OOH despite early recommendations.  

Clean all glassware sequentially in soap solution, water, and acetone. Allow the acetone to evaporate and then dry everything in an electric 

Put the ( )-geraniol 7 (8.2 g, 9.2 mL, 53 mmol) into a 50 mL Erlenmeyer flask along with 25 mL of dichloromethane and some 4 A molecular sieves (2-4 g, mass unimportant). Stopper the flask and set it aside to pre-dry the substrate. 

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