CHIRAL SYNTHESIS VIA ORGANOBORANES .40. SELECTIVE REDUCTIONS .55. A SIMPLE ONE-POT SYNTHESIS OF THE ENANTIOMERS OF (TRIFLUOROMETHYL)OXIRANE- A GENERAL-SYNTHESIS IN HIGH OPTICAL PURITIES OF ALPHA-TRIFLUOROMETHYL SECONDARY ALCOHOLS VIA THE RING-CLEAVAGE REACTIONS OF THE EPOXIDE

An extremely efficient one-pot asymmetric synthesis of either enantiom er of (trifluoramethyl)oxirane (3,3,3-trifluoro-1,2-epoxypropane, 4) i n 64% yield and 96% ee has been achieved via the asymmetric reduction of the commercially available 1-bromo-3,3,3-trifluoro-2-propanone with either (+)- or (-)-B-chlorodiisopinocampheylborane (Aldrich: DIP-Chlo ride), followed by ring closure of the intermediate chloroborinate, Ip cBCl[OCH(CH2Br)CF3]. The ring cleavage reactions of 4 provide a genera l synthesis of chiral trifluoromethyl carbinols without loss of optica l activity. Thus we have synthesized 1-amino-3,3,3-trifluoro-2-propano l, 1-azido-3,3,3-trifluoro-2-propanol, 1-(diethylamino)3,3,3-trifluoro -2-propanol, 1-cyano-3,3,3-trifluoro-2-propanol, 1,1,1-trifluoro-2-pro panol, 1,1,1-trifluoro-2-octanol, 1-phenyl-3,3,3-trifluoro-2-propanol, 1-ethoxy-3,3,3-trifluoro-2-propanol, and 1,2-dihydroxy-3,3,3-trifluor apropane, in 61-88% yields and in 96% ee by the cleavage of 4 with the appropriate nucleophile.