HIGHLY STEREOSELECTIVE SYNTHESIS OF TRIFLUOROMETHYLATED COMPOUNDS VIAESTER-ENOLATE [2,3]-WITTIG AND [3,3]-IRELAND-CLAISEN REARRANGEMENTS

gamma-Trifluoromethylated propargylic alcohols have been obtained in o ptically pure forms via effective enzymatic kinetic resolution and the n converted into (E)- or (Z)-allylic alcohols. [2,3]-Wittig rearrangem ent of the corresponding [[gamma-(trifluoromethyl)allyl]oxy] acetic ac id methyl esters afforded oxy-beta-(trifluoromethyl)-gamma,delta-unsat urated carboxylic acid methyl esters in good yields. The rearrangement of (Z)-substrates proceeded in a highly stereoselective manner to giv e anti-isomers with E configuration at a newly created olefinic bond v ia complete chirality transfer. (E)-Substrates, however, showed relati vely low stereoselectivities resulting in mixtures of syn- and anti-pr oducts. The trifluoromethylated allylic alcohols were also converted i nto the corresponding a-methoxyacetic acid gamma-(trifluoromethyl)ally l esters and evaluated as substrates for [3,3]-Ireland-Claisen rearran gement. (E)-Substrates were efficiently transformed into syn-products while (Z)-substrates exhibited relatively low stereoselectivities. The two complementary methods provide facile routes to highly functionali zed trifluoromethyl-containing molecules with a high degree of stereoc ontrol.