Evidence for the Formation and Structure of Palladacycles during Pd-Catalyzed CN Bond Formation with Catalysts Derived from Bulky Monophosphinobiaryl Ligands

✍ Scribed by Eric R. Strieter; Stephen L. Buchwald

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 254 KB
• Volume: 45
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.200502927

✦ Synopsis

One of the most general catalyst systems, in terms of their efficacy in CÀC, CÀN, and CÀO bond-forming reactions, are those based on the bulky, electron-rich monophosphinobiaryl ligands (Scheme 1). [1] First introduced in 1998, the Pd 0 catalyst based on 1 a demonstrated exceptionally high activity, thereby allowing room-temperature Suzuki-Miyaura couplings of aryl bromides and chlorides as well as room-temperature aminations of aryl bromides, including the first room-temperature amination of an aryl chloride. [2] While searching for catalysts that display higher turnover numbers (TONs) than those observed with 1 a, ligand 2 was discovered, thus further expanding the scope of these cross-coupling reactions. [3] More recently, with the introduction of 3 a and 3 b into this class of ligands, the most general and active catalyst systems to date for Suzuki-Miyaura couplings, CÀN bond-forming reactions, and Sonogashira reactions with aryl chlorides and tosylates have been revealed. [4] Scheme 1. Bulky, electron-rich monophosphinobiaryl ligands used in Pd-catalyzed CÀC, CÀN, and CÀO bond-forming reactions. Cy = cyclohexyl.