P19 超音波照射を用いた金属による有機合成への活用(ポスター発表)

抄録

Various metals were used for organic synthesis with ultasonication. Zinc showed the extreme effect for the C-C coupling reaction. Various ketones were reductively coupled to give the corresponding pinacole. Ketones were substituted with methyl, hydroxyl, acetoxy, halogen and amines on the benzene ring. The typical reaction was achieved as follows. Substituted acetophenones were dissolved in THF. The solution was added with TiCl_4 and Zn in THF at 0℃ and the reaction mixture was ultrasonicated under argon. The reaction mixture was added by sodium hydrogencarbonate solution and extracted with ethyl acetate. The ethyl acetate extracts were concentrated in vacuo and the concentrated solution was chromatographed over silica gel and eluted with hexane-ethyl acetate to give the corresponding pinacol. The pinacol changed to the corresponding pinacolone using strong acid, but pinacol did not change easily to pinacolone using ultrasonication with TiCl_4 in short time. In the case of acetophenone, the corresponding pinacol was obtained in 75% for 2h without using ultrasonication, however by using ultrasonication the same reductive coupling reaction of acetophenone was achieved in 90% only for 10 min. When acetophenone substituted with nitro group was used as the substitute, the nitropinacol produced in the reaction was easily reduced to aminopinachol in the reductive coupling. Reductive coupling of fluoroacetophenone showed high yield.