The Study On Knoevenagel Reaction Of α-Fluorinated Gem-diols With Aldehydes

This paper focused on the synthesis of trifluoromethyl α-fluorinated gem-diols starting from trifluoromethyl1,3-dicarbonyl compounds. The fluorination reaction between trifluoromethyl1,3-dicarbonyl compounds and electrophilic fluorinating reagents selectfluor gave a series of trifluoromethyl α-fluorinated gem-diols in the yield of42.3-53.6%and the purity were above97%.This paper also studied on the nucleophilic addition reaction of α-fluorinated gem-diols with aldehydes. Due to the Strong electron-withdrawing properties of trifluoromethyl, we could get a series of α-fluorochalcone with a high Z/E ratio through the facile release of trifluoroacetate which occurs by C-C bond scission. After finding the best reaction conditions, some other extended α-fluorinated gem-diols substrates reacted with benzaldehyde, p-bromobenzaldehyde, p-nitrobenzaldehyde, furfuraldehyde, p-methoxy benzaldehyde, m-nitrobenzaldehyde to get a series of α-fluorochalcone in the yield of35.4%～87.6%and the Z/E ratio of90.0%～100%. Studies showed that it was a simple synthesis method for Z α-fluorochalcone and also had a wide applicability. The reaction mechanism was discussed at last.