Investigation On Organic Reactions In High-temperature Water

Currently,the protection of environment has been gaining increasing attention.High temperature liquid water is a kind of green solvent with great application potential.The definition of high temperature water(HTW)is broad,usually it refers to compressed water at the temperature range from 100 ℃ to the critical point,and at the supercritical state(temperature> 374 ℃,pressure> 218 atm).Under this kind of conditions of high temperature and high pressure,the various physical and chemical properties of water change accordingly,such as the decrease of dielectric constant,density and viscosity,the increase of mass transfer capacity,so that it has good solubleness for both organic and inorganic substances,in which many organic reactions can be carried out.In these cases,HTW is not only the solvent of the reaction,but also is one of the reactants and catalysts of the reactions.The fact that water under this state is widely used as an organic reaction medium has gained attention and has been widely studied.In this paper,three reaction systems with high temperature water as the reaction medium are studied.The first part is on the reduction reaction of benzophenone compounds in high temperature water.The second part is on the reaction of toluene compounds being oxidized into aldehyde in high temperature water.The third part is on the synthesis reaction of quinazolinones in high temperature water.Firstly,the reduction reaction of benzophenone compounds in high temperature water was studied(Scheme 1).The generally methods for the reduction of such compounds were as follows: zinc powder was used as a reductant and with methanol as solvent,or using palladium as catalyst under high pressure conditions,or using sodium borohydride as a catalyst with tetrahydrofuran as solvent.In this paper,water was used as solvent,and the appropriate reduction reagent was selected by experiments.Then,the reaction temperature,reaction time,amount of zinc powder and water were studied respectively.The optimized reaction conditions were as follows: the reaction temperature was 160 ℃,the reaction time was 8 h,the molar ratio of zinc powder and benzophenone was 3:1,the reaction yield was 70.2%.The reduction reaction of benzophenone with different substituents was continue studied,and the yields were 30.4%~72.5%.The advantages of this method is that it is simple in both operation and post-processing.Secondly,the oxidation reaction of toluene compounds to aromatic aldehydes in high temperature water was studied(Scheme 2).Potassium permanganate or manganese dioxide were employed as oxidant for the synthesis of such compounds,and chlorination-hydrolysis method is also suitable too.In order to reduce pollution,the researches on new methods have been on-going constantly,such as the electro-chemical methods,enzymatic and bionic liquid phase oxygen oxidation and so on.In this paper,water was used as the reaction solvent and hydrogen peroxide as the oxidant to oxidize the toluene compounds into aromatic aldehydes.The experimental results showd that the optimum conditions were as follows: the reaction temperature was 170 ℃,the reaction time was 4 h,the molar ratio of raw material to oxidant was 1:4,and the yield of p-chlorobenzaldehyde was 53.1%.The reactions of oxidizing several toluene derivatives into aldehydes are further studied,and the yields were 9%~53.1%.This method is simple in operation and post-processing,and is with little pollution.Thirdly,the synthesis of quinazolinones in high temperature water was studied(Scheme 3).Quinazolinones were an important class of compounds,which were widely distributed in nature,and has certain physiological activity in the anti-cancer,anti-tumor and anti-inflammatory treatment.In a conventional way,quinazolinones can be obtained with NH4 Cl as catalyst and ethanol as solvent as well as with Ga(OTf)3 as catalyst and with DMSO as solvent.In this paper,high temperature water was used as the reaction solvent.The effects of reaction time,reaction temperature and molar ratio of reactants on the reaction yield were studied.The experimental results showd that the optimizedconditions were as follows: the reaction temperature was 130 ℃,the reaction time was 1 h,the molar ratio of reagents was 1:1,the amount of water was 4 m L,and the yield of product was 85.7%.And then the reaction of 2-aminobenzamide with different aldehydes was further studied,and the yields were 32.4%~85.7%.