TY - JOUR ID - 15442 TI - A Highly Diastereoselective and Enantioselective Phase-Transfer Catalyzed Epoxidation of β-Trifluoromethyl-β,β-disubstituted Enones with H2O2 JO - Iranian Journal of Chemistry and Chemical Engineering JA - IJCCE LA - en SN - 1021-9986 AU - Wu, Shaoxiang AU - Wang, Qi AU - Wang, Yao-Feng AU - Karmaker, Pran Gopal AU - Chen, Fu-Xue AD - School of Chemical Engineering & the Environment, Beijing Institute of Technology, Haidian District, Beijing 100081, CHINA Y1 - 2015 PY - 2015 VL - 34 IS - 4 SP - 13 EP - 38 KW - Asymmetric catalysis KW - Epoxidation KW - Hydrogen peroxide KW - Phase transfer catalyst KW - Trifluoromethyl DO - 10.30492/ijcce.2015.15442 N2 - Trifluoromethylated organic compounds, especially chiral quaternary alcohols bearing trifluoromethyl group are of important intermediates in drugs, agrochemicals and etc.An efficient epoxidation of β-CF3-β,β-disubstituted unsaturated ketones (6) has been developed with environmental benign hydrogen peroxide as the oxidant and F5-substituted chiral quaternary ammonium salt (1g or 5) derived from cinchona-alkaloid as the catalyst. Using 3 mol% of the catalyst, both enantiomers of(R,R) and (S,S) β-trifluoromethyl-α,β-epoxy ketones (7, 8) were obtained in excellent diastereoselectivities (up to 100:1 d.r.) and enantioselectivities (up to 99.7% ee). The effects of catalyst structure, catalyst loading, substrate structure, the nature of oxidant, and reaction conditions on the catalyst capacities have been discussed in full length. The reaction mechanism was proposed to explain the origin of chiral induction. By subsequent reduction with zinc the epoxides are exhibited to be converted into trifluoromethylated quaternary alcohols without any loss in enantioselectivities. All new compounds are fully characterized by IR, NMR, elemental analysis and or high resolution mass spectrum. UR - https://ijcce.ac.ir/article_15442.html L1 - https://ijcce.ac.ir/article_15442_cc2bb0401796f5ff057870127c17c94b.pdf ER -