Synthesis of 2,3- or 1,2-unsaturated derivatives of 2-deoxy-2-trifluoromethylhexopyranoses

The attempted conversion, by treatment with CsF/TBFA in MeCN, of acetylated derivatives of 2-chlorodifluoromethyl-2-deoxyhexopyranoses into their corresponding 2-trifluoromethyl derivatives was always accompanied by an elimination reaction. Thus, representative educts with the D-gluco- and D-manno-configuration gave derivatives of 2,3-dideoxy-2-trifluoromethyl-D-erythro-hex-2-enopyranose and 1,5-anhydro-2-deoxy-2-trifluoromethyl-d-arabino-hex-1-enitol, respectively. X-ray analyses are given for 1,3,4,6-tetra-O-acetyl-2-chlorodifluoromethyl-2-deoxy-alpha-D-mannopyranose and 4,6-di-O-acetyl-2,3-dideoxy-2-trifluoromethyl-alpha-D-erythro-hex-2-enopyranose.