Samarium Diodide Promoted Reductive Coupling Reactions of Ethyl 2-Thiophenecarboxylate with Ketones. Applications to the Synthesis of Liquid Crystals and Photochromism.

• Main Authors: Jiun-Jie Shie, 謝俊結
• Other Authors: Jim-Min Fang
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/27199427311265120771

碩士 === 國立臺灣大學 === 化學研究所 === 90 === Abstract In this thesie, I describe the reductive double electrophilic coupling reactions of ethyl thiophene-2-carboxylate and ketones promoted by SmI2/HMPA and application of these compounds in the areas of liquid crystals and photochromism are under study. Ethyl thiophene-2-carboxylate underwent the reductive double electrophilic coupling reactions with aryl ketones by promotion of SmI2/HMPA to give disubstituted 4,5-dihydrothiophene-2-carboxylates in high regio- and stereoselective manner. The products obtained from the reductive double electrophilic reactions of ethyl thiophene-2-carboxylate were converted to thiophene-fused p-terphenyls, polybenz[b]thiophenes and thiophene-fused polycyclic compounds via sequential oxidation-electrocyclization-oxidation reactions. The SmI2-promoted coupling reactions of ethyl thiophene- 2-carboxylate with aryl ketones, followed by acid-catalyzed dehydration and oxidative aromatization gave dialkenylthiophenes M which under went electrocyclizations upon irradiation to give the corresponding closed-ring species N constitutes a novel photochromic system. By a simplar procedure, dienes 37, trienes 38 and benzothiophenes 39 bearing long-chain substitutents were prepared. Among them, dienes 37 and trienes 38 possess the liquid crystalline properties of smectic-A type. Thieno-p-terphyls 39 exist as solids with rather high melting points, even though they are equipped with soft long chains of decoxy, dedecoxy, tetradecoxy and hexadecoxy groups. By comparison with the thienyl rings in 37 and 38, the rigid core of benzothiophene is longer to disfavor the liquid-crystalline property.