Directing/Protecting‐Group‐Free Synthesis of Tetraaryl‐Substituted Pyrazoles through Four Direct Arylations on an Unsubstituted Pyrazole Scaffold |
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| Authors: | Dr Shinichiro Fuse Taiki Morita Dr Kohei Johmoto Dr Hidehiro Uekusa Dr Hiroshi Tanaka |
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| Affiliation: | 1. Department of Applied Chemistry, Tokyo Institute of Technology, 2‐12‐1, Ookayama, Meguro‐ku, Tokyo 152‐8552 (Japan);2. Present address: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta‐cho, Midori‐ku, Yokohama 226‐8503 (Japan);3. Department of Chemistry and Materials Science, Tokyo Institute of Technology, 2‐12‐1, Ookayama, Meguro‐ku, Tokyo 152‐8552 (Japan) |
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| Abstract: | A directing/protecting‐group‐free synthesis of 1,3,4,5‐tetraaryl‐substituted pyrazoles was achieved through four transition metal‐catalyzed direct arylations. Various pyrazoles with four different aryl rings were obtained using readily available reagents from an unsubstituted pyrazole. Two aryl‐substituted pyrazoles showed intense violet fluorescence, high quantum yields (Φf=0.68, 0.64), and large Stokes shifts (19000, 15200 cm?1). |
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| Keywords: | C H activation cross‐coupling fluorescence heterocycles palladium |
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