Issue in Honor of Prof. (Mrs.) Asima Chatterjee ARKIVOC 2003 (ix) 87-95 Pyrazole-based P,N-ligand for palladium catalyst : applications in Suzuki coupling and amination reactions Anuradha Mukherjee and Amitabha Sarkar ¶ * Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta-700 032, India E-mail: ocas@ iacs.res.in Dedicated to Professor Asima Chatterjee on the occasion of her 85 th birthday (received 03 Dec 03; accepted 17 Feb 04; published on the web 28 Feb 04) Abstract A new pyrazole-tethered phosphine ligand has been used for efficient palladium-catalyzed Suzuki coupling between phenylboronic acids and aryl halides. The same ligand also facilitates palladium-catalyzed amination of aryl bromide or triflate. Keywords: Suzuki coupling, amination, pyrazole, palladium, catalyst, P, N-ligand Introduction Palladium catalyzed coupling reactions are extremely powerful tools to construct new C-C and C-N bonds. The mild reaction conditions of these reactions offer considerable advantages over classical methods, that require either activated molecules or harsh reaction conditions. Recently, significant developments in Suzuki coupling reaction 1 and amination of aryl halide or triflate have been reported by Buchwald 2 and Hartwig 3 . That stereoelectronic effects and the bite angle 4 of the employed ligands are significant factors for efficient coupling reactions, have been illustrated by a recent set of electron-rich and functionalized phosphine ligands displayed in Fig- 1. For example, Buchwald has shown that 2-dicyclohexylphosphanyl-2′-dimethylaminobiphenyl, ii, is an excellent ligand 2e,2f for coupling of aryl bromides and chlorides with boronic acids at room temperature. ¶ Present address: Department of Organic Chemistry, Indian Association for the Cultivation of Science, Kolkata, India. e-mail: ocas@mahendra.iacs.res.in ISSN 1551-7012 Page 87 © ARKAT USA, Inc