A novel photochromic system of 4,5-dialkenylthiophenes constructed by the smarium diiodide promoted coupling reactions of thiophene-2-carboxylate with aryl ketones.
[reaction: see text] The SmI2-promoted coupling reaction of ethyl thiophene-2-carboxylate with aryl ketones (2 equiv), followed by acid-catalyzed dehydration and oxidative aromatization, gave dialkenylthiophenes 1b-d, which underwent electrocyclizations upon irradiation with 300-nm light in CH3CN solution to give the corresponding closed-ring species with absorption lambda(max) approximately 425 nm. The interconversion between dialkenylthiophenes and their corresponding closed-ring species constitutes a novel photochromic system bearing an ester group for potential uses in linkage and wavelength tuning.
Shie
Jiun-Jie
JJ
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, Republic of China.
Yang
Shyh-Ming
SM
Chen
Chao-Tsen
CT
Fang
Jim-Min
JM