Study on Acid-Catalyzed Photochemical Reactions of Stilbene Derivatives and Analogues

• Main Authors: HO, JINN-HSUAN, 何郡軒
• Other Authors: HO, TONG-ING
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/25463960598327418272

博士 === 國立臺灣大學 === 化學研究所 === 89 === This work mainly studies on the photochemical reaction of stilbene derivatives and analogues. In acetonitrile, stilbene derivatives and analogues can undergo a novel photorearrangement reaction by one equivalent hydrochloric acid catalyzed. The mechanism of this reaction has been proposed for via six-electron ring-closure, an apparent [1,9]H shift of acid-catalyzed proton addition-elimination reaction, six-electron ring-open, and finally hydrolysis of methyl vinyl ether to obtain a new series of products 4-aryl-but-3-en-2-one and analogues. Some stilbene derivatives can react with the products, 4-arylbut- 3-en-2-one, in acetonitrile, then produce the single-bond products 4-arylbutan-2-one and the oxidative cyclization products of stilbene derivatives. In acetonitrile, stilbene derivatives and analogues can undergo another novel photorearrangement reaction by excess hydrochloric acid catalyzed. The mechanism of this reaction has been proposed for via six-electron ring-closure, an apparent [1,9]H shift of acid-catalyzed proton addition-elimination reaction, hydrolysis of intermediate, methyl alkenyl ether, and an apparent [1,3]H shift of acid-catalyzed proton addition-elimination reaction. Then another new series of products 1,2,3-trihydrophenanthren-3-one and analogues were obtained. There is a reactive intermediate, which possesses two reaction pathways, in the photorearrangement of stilbene derivatives and analogues in acetonitrile. These two reaction pathways of the intermediate are six-electron ring-opening reaction and hydrolysis of methyl alkenyl ether, respectively. Since the reaction rate of hydrolysis of methyl alkenyl ether is very sensitive to the concentration of acids, changing the acid concentration can control the reaction pathways of this intermediate. Therefore, we successfully control these two competitive reaction pathways by changing acid concentration, and discover this reaction is a very good acid-catalyzed photochemical switching reaction. Using 2-methoxystyrylaromatics and heterocycles as reactants, the reaction can produce these two type products, 1-arylbut-2-en-1-one and 2,3,4-trihydrophenanthren-1-one, via irradiation with no matter excess or catalytic acids. But it cannot give any photorearrangement product by using 3-methoxystyrylfuran. Irradiating 4-halostyrylfurans and thiophenes in acetonitrile with excess acids for a long time, it can produce two type photorearrangement products. One is 4-arylbut-3-en-2-one and the other is 8-halo-6,9-dihydronaphtho[2,1-b]furan or thiophene. But it can get 1-aryl-3-halo-butadiene when the reactant was irradiated with catalytic acids for a short time. When 4-methoxydiphenylamine was irradiated with catalytic acids, the photorearrangement reaction can also be proceeded and produce a new product, 1,2,4-trihydrocarbazol-3-one.