1218819-06-7Relevant articles and documents
Subsequent chemical reactions of photochromic 4,5-dibenzothienylthiazoles
Nakagawa, Hisako,Nakashima, Takuya,Kawai, Tsuyoshi
, p. 4493 - 4500,8 (2020/08/31)
4,5-Dibenzothienylthiazole derivatives having leaving groups at the reactive 2-positions of benzothiophene rings have been synthesized, and their photochromic ring-closing reaction followed by spontaneous elimination and substitution reactions have been studied. A 4,5-dibenzothienylthiazole having an ethoxy group and a hydrogen atom at each 2-position of the benzothienyl ring underwent elimination to generate a condensed aromatic structure upon the addition of acid. 4,5-Dibenzothienylthiazoles having an ethoxy or methyl groups at the 2-position of the benzothienyl rings showed photochromism both in hexane and in methanol solutions with photocyclization quantum yields as high as 60 %. Upon the addition of acid to the methanol solutions of closed-ring isomers of dibenzothienylthiazoles, the substitution of the ethoxy group with a methoxy group occurred. The generation and rearrangement of the carbocation intermediate formed by elimination of the ethoxy group from the closed-ring isomers were apparent from the chemical structure of methoxy-substituted products. Subsequent chemical reactions are demonstrated for photoproducts of 4,5- dibenzothienylthiazoles possessing leaving groups at the 2-position of benzothienyl rings. Closed-ring isomers of 4,5-dibenzothienylthiazoles having an ethoxy group underwent an alcoholysis reaction under acidic conditions accompanying rearrangement of carbocation intermediates. Copyright
