Studies On Synthesis Of Isochromanone,Xanthone And Thioxanthone By Ferric Nitrate

Isochromanones,xanthones and thioxanthones are widely used in the field of medicine,agronomy,chemicals and functional materials.Therefore,it is full of significance to develop a simply and efficient approach for the synthesis of isochromanone,xanthone and thioxanthone.This study mainly adopts the method for direct synthesis of isochromanone,xanthone and thioxanthone via benzyl oxidation.Firstly,phenylethyl alcohols were used as raw material to prepare isochromans through two steps;Salicylic aldehydes and cyclohexene ketones were used as raw material to prepare xanthene by oxidative coupling reactions;Thioxanthones were used as raw material to prepare thioxanthenes by using the method of reduction reaction.Secondly,the Fe?NO₃?₃·9H₂O/KPF6/O₂ catalytic system was developed for the preparation of isochromanones.With isochromanene as the model substrate,the reaction conditions,including the effect of solvents,the kind of catalysts,the reaction temperature,oxygen,the amount of catalysts and acid salt were screened.On the basis of these experimental data,we concluded that 10 mol% Fe?NO₃?₃·9H₂O,15 mol% KPF6 in 3 mL CH3 CN at 80 oC was suitable for oxidation of isochromanene to isochromanone under atmospheric pressure of O₂.Under the optimal reaction conditions,isochromanone was isolated in 94% yield.Different substituted isochromanone were also examined,and a broad range of corresponding isochromanone were obtained in 46-95% yield.At last,the Fe?NO₃?₃·9H₂O/KPF6/O₂ catalytic system was applied to the synthesis of the xanthones and thioxanthones.Most of the substrates can also be easily converted to corresponding target products in 91-97% isolated yield under optimal conditions in 2 h.Because of the bad solubility of some substituted xanthenes,increasing the dosage of CH3 CN and catalyst,and prolonging the reaction time is essential.In addition,a plausible reaction mechanism was proposed according to the literatures and the results of several control experiments.In conclusion,we have developed a method for synthesis of isochromanones,xanthones and thioxanthones successfully.This catalytic system showed high activity and selectivity.However,this study didn't refer to the preparation of azaanthenones.