Directing/protecting-group-free synthesis of tetraaryl-substituted pyrazoles through four direct arylations on an unsubstituted pyrazole scaffold.
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) ).
Department of Applied Chemistry, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552 (Japan). sfuse@res.titech.ac.jp.|Present address: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan). sfuse@res.titech.ac.jp.
Shinichiro
S
Fuse
Department of Applied Chemistry, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552 (Japan).
Taiki
T
Morita
Department of Chemistry and Materials Science, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552 (Japan).
Kohei
K
Johmoto
Department of Chemistry and Materials Science, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552 (Japan).
Hidehiro
H
Uekusa
Department of Applied Chemistry, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552 (Japan).
Hiroshi
H
Tanaka
CH activation; cross-coupling; fluorescence; heterocycles; palladium