| In view of increasingly severe environmental problems,the clean manufacture of chemical products is of important practical significance.The aromatic F-C benzylation products,diarylmethanes,and their derivatives are very commercially significant fine chemicals,which are widely used in phamaceuticals,dyes,perfumes and other industries.However,there are pollution and corrosion problems in the industrial preparation methods of diarylmethanes.The ideas of acidic functional ionic liquids design were employed in this paper to achieve clean aromatic F-C benzylation.（1）A kind of novel Br?nsted-Lewis acidic catalysts with ionic liquid-like structures were prepared by combining sulfonated organic cations,MIMPS+,PYPS+or TEAPS+,and metal cations,Ga3+,Hf4+,with Lewis acidity into phosphotungstic anions.The structures,acid properties and thermal stabilities of the heteropoly ionic liquids were characterized by FT-IR,Py-IR,XRD,TG-DTG,BET and ICP techniques.F-C benzylation of p-xylene with benzyl alcohol was carried out using the above heteropoly ionic liquid catalysts.Under the optimized reaction conditions(0.10 g of Hf0.50[TEAPS]PW12O40 catalyst,0.01 mol of benzyl alcohol,n（p-xylene）:n（benzyl alcohol）=12,140℃,2 h),the conversion of benzyl alcohol was 100%and the selectivity for monobenzylation was 92.4%.The catalyst Hf0.50[TEAPS]PW12O40 could keep a good catalytic performance after recyclings of 5times.Moreover,good catalytic performances were also obtained when Hf0.50[TEAPS]PW12O40 was used in the F-C benzylation of different aromatic substrates.（2）Deep eutectic solvents with Br?nsted acidity were prepared by binding hydrogen bond donors with different Br?nsted acid strength such as TfOH and CH3SO3H,with hydrogen bond acceptors such as choline chloride（ChCl）and tetramethylammonium chloride（TMAC）.The deep eutectic solvents prepared from TfOH exhibited both water tolerance and strong acidity.The structure,acid properties and thermal stabilities of some deep eutectic solvents were characterized by FT-IR、1H NMR、TG-DTG techniques,and there general physical parameters were also tested.F-C benzylation of p-xylene with benzyl alcohol was carried out over[ChCl][TfOH]2.Under optimized reaction conditions（0.10 g of[ChCl][TfOH]2 catalyst,0.01 mol of benzyl alcohol,n（p-xylene）:n（benzyl alcohol）=15,140℃,1 h）,the conversion of benzyl alcohol was 100%and the selectivity for monobenzylation was 91.5%.The catalyst[ChCl][TfOH]2 showed the characteristics of reaction control phase separation in this system,and good catalytic performance after 6 cycles.（3）Deep eutectic solvents with Lewis acidity were prepared by combining InCl3or SnCl2 with hydrogen bond acceptors such as choline chloride（ChCl）or acetamide acacarboxylic acid（ACA）.The deep eutectic solvents prepared from In Cl3 exhibited both water tolerance and strong acidity.The structures,acid properties and thermal stabilities of some Lewis acidic deep eutectic solvents were characterized by FT-IR,acetonitrile IR spectrum,TG-DTG techniques,and their solubility data were also tested.The F-C benzylation of anisole with benzyl alcohol was carried out using[ACA][InCl3]1.4 as a catalyst.Under optimized reaction conditions(0.37 g of[ACA][InCl3]1.4 catalyst,0.01 mol of benzyl alcohol,n（anisole）:n（benzyl alcohol）=15,140℃,6 h),the conversion of benzyl alcohol was 99.3%and the selectivity for monobenzylation was 95.2%.The thermal stability of[ACA][InCl3]1.4 catalyst is a limiting factor for recycling performance.Three types of ionic liquid-like catalysts have been successfully synthesized to catalyze the clean F-C benzylation with good catalytic and separation performance.Thus,an environmentally friendly route of F-C benzylation reaction with high atomic economy has been developed. |
