Regioselective and chemoselective epoxidation of fluorinated monoterpenes and sesquiterpenes by dioxiranes

A comparative study on chemoselectivity of dimethyldioxirane (DMD) and methyl(trifluoromethyI)dioxirane (TFMD) in the epoxidation of trisubstitukd C=C bonds presenting different activation in fluorinated monoterpene and sesquiterpene derivatives has been carried out. With respect to DMD, epoxidations performed with TFMD were faster under milder conditions, although high conversion yields were obtained with both reagents. In ease of epoxidation of unsaturated moieties the trend observed was: (CH3(R1)C=CH(R2) ca. (CH3)(R1)C=CH(CH20R) ca. (CH3)(R1)C=CF(R2) >> (CH3)(R1)C=CH(COOR) > (CF3)(R1)C=CH(R2). Results reported herein present the first example of direct epoxidation of a double bond bearing a CF3 substituent by non-biochemical means.