Amino Acid-catalyzed Double Bond Isomerization Of (E)-2,4-diaryl-1,1,1-trifluoro-2-butenes

The presence of fluorine atoms in organic molecules has a great impact on their physical and biological properties and chemical reactivity.Therefore,fluorine-containing compounds have received considerable attention in the field of life sciences and the design of advanced functional materials.It is necessary to develop new methods for the synthesis of fluorinecontaining compounds.Due to the strong electron absorption and stable C-F bond of trifluoromethyl group,trifluoromethyl group compounds also play an important role in drug molecules and the development of high-performance materials.In the previous research,our research group synthesized a series of(Z)-trifluoromethyl alkenyl triflates with various functional groups in a simple and efficient manner using the "twostep one-pot method",and successfully used this bulding block in the synthesis of various fluorine-containing compounds.Among them,(E)-1,3-diaryl-4,4,4-trifluoro-1-butenes can be synthesized from 4-aryl-1,1,1-trifluoroprene-2-ene-2-yl trifluoromethanesulfonates by Stille coupling and palladium catalyzed isomerization of carbon carbon double bond.However,the step of double bond position isomerization requires 40 mol% of palladium acetate and the bisphosphine ligand 4,5-bisdiphenylphosphine-9,9-dimethylxanthene as a catalyst,which greatly limits its application.Therefore,this thesis studies the double bond isomerization of(E)-2,4-diaryl-1,1,1-trifluoro-2-butene catalyzed by amino acids,and explores more effective ways to catalyze the double bond isomerization.Firstly,trifluoromethylenol(Z)-trifluoromethyl sulfonate was synthesized by trifluoromethyl sulfonic anhydride capturing trifluoromethylenol anions generated in the exchange reaction of ethyl trifluoroacetate/aryl ketone.The substrate(E)-2,4-diaryl-1,1,1-trifluoro-2-butene was synthesized by Suzuki coupling reaction in the absence of alkali.Then,a series of(E)-1,3-diaryl-4,4,4-trifluoro-1-butene compounds were synthesized by isomerization of olefins with amino acid as catalyst.The effects of different amino acids and dosage,reaction temperature,reaction solvent and reaction time on the yield were investigated,and the optimal reaction conditions were determined,that is,(E)-2,4-diaryl-1,1,1-trifluoro-2-butene and L-proline(20 mol%)were mixed in DMF,and then reacted at 80 ℃ for 36 h.The reaction of different substrates showed that the substrates with alkoxy,carboxyl,halogen,cyano and alkyl groups on the 2-and 4-position aromatic ring could react smoothly,and the separation yield was as high as 94%.