Journal of Organic Chemistry p. 5437 - 5442 (1991)
Update date:2022-07-29
Topics:
Huang, C.-G.
Shukla, Deepak
Wan, Peter
A new photoreaction, the photoisomerization of xanthene (1) to 6H-dibenzopyran (2) (ca. 70percent) (Φ = 0.0035 in 7:3 H2O-CH3CN) in aqueous CH3CN solution is reported.In addition to 2, 2-benzylphenol (3) (Φ ca. 0.001), 9,9'-bixanthyl (4) (Φ < 0.001), and 2-(2'-hydroxyphenyl)benzyl alcohol (5) (Φ < 0.001) are also observed as minor products. 9-Methylxanthene (9) also photoisomerizes to the corresponding pyran derivative 10, although in this case much lower yields are observed due to secondary photochemistry of 10.The photoisomerization of 1 is most efficient in aqueous solution: Φ increased with increasing water content in a H2O-CH3CN solvent mixture.A mechanism of photoisomerization is proposed that involves initial Ar-O bond homolysis from S1, to generate a singlet biradical.Trivial recombination gives back unreacted 1.Hydrogen abstraction from solvent leads to the photoreduction product 3.However, recombination of the biradical at the ipso benzylic position (ortho to phenol) gives a cyclohexadienone intermediate 17.Subsequent transformation of this species to 2 occurs via an o-quinone methide intermediate 18, which itself can be trapped with MeOH or H2O, to give the corresponding methyl ether derivative 8 or alcohol 5.
View MoreSHANDONG CREDAGRI CHEMICAL CO., LTD.
Contact:+86-531-88872050
Address:ROOM 601A, BUILDING 2, SHUNTAI SQUARE, NO. 2000 SHUNHUA ROAD, HI-TECH DEVELOPMENT ZONE, JINAN, CHINA.
Hangzhou Hysen Pharma co.,Ltd.
website:http://www.hysenpharma.cn/
Contact:0086-571-88298791
Address:#701,Gudun Road Hangzhou
Shanghai Xinda Pharmaceuticals Co., Ltd.
Contact:86-21-33692333-8008
Address:999 Linxian Road, Jinshan Industrial Park, Shanghai, China
Contact:+86-633-8332928
Address:No.1,Huanghai Yilu.Rizhao,Shandong
Hubei Xinjing New Material Co.,Ltd
Contact:+86-27-83313147
Address:Room402.#Bthe 7th,Headquarter of Huifeng Corporation Qiaokou District,Wuhan China
Doi:10.1016/j.bmc.2011.09.052
(2011)Doi:10.1002/hlca.201100105
(2011)Doi:10.3390/molecules20034764
(2015)Doi:10.1021/acscatal.9b02316
(2019)Doi:10.1021/ja00019a016
(1991)Doi:10.1039/c39940001681
(1994)