ABSTRACT
The palladium-catalyzed borylation of aryl and heteroaryl halides with a novel borylating agent, tetrakis(dimethylamino)diboron [(Me(2)N)(2)B-B(NMe(2))(2)], is reported. The method is complementary to the previously reported method utilizing bis-boronic acid (BBA) in that certain substrates perform better under one set of optimized reaction conditions than the other. Because tetrakis(dimethylamino)diboron is the synthetic precursor to both BBA and bis(pinacolato)diboron (B(2)Pin(2)), the new method represents a more atom-economical and efficient approach to current borylation methods.
Subject(s)
Boron Compounds/chemical synthesis , Hydrocarbons, Halogenated/chemical synthesis , Palladium/chemistry , Boron Compounds/chemistry , Catalysis , Combinatorial Chemistry Techniques , Hydrocarbons, Halogenated/chemistry , Molecular StructureABSTRACT
The use of bis-boronic acid for the direct synthesis of boronic acids has greatly facilitated the two-step, one-pot borylation/Suzuki cross-coupling reaction between aryl and heteroaryl halides. With use of Buchwald's second-generation XPhos preformed catalyst, high yields of cross-coupled products were obtained for most substrates. The method also allows an efficient two-step, one-pot synthesis, providing access to three distinct cross-coupled products after column chromatography. The method also provides a rapid and convenient route to teraryl compounds.
Subject(s)
Boronic Acids/chemistry , Cross-Linking Reagents/chemistry , Cross-Linking Reagents/chemical synthesis , Hydrocarbons, Halogenated/chemistry , Palladium/chemistry , Catalysis , Chromatography, Liquid/methods , Molecular StructureABSTRACT
The Suzuki-Miyaura reaction has become one of the more useful tools for synthetic organic chemists. Until recently, there did not exist a direct way to make the most important component in the coupling reaction, namely the boronic acid. Current methods to make boronic acids often employ harsh or wasteful reagents to prepare boronic acid derivatives and require additional steps to afford the desired boronic acid. The scope of the previously reported palladium-catalyzed, direct boronic acid synthesis is unveiled, which includes a wide array of synthetically useful aryl electrophiles. It makes use of the newly available second generation Buchwald XPhos preformed palladium catalyst and bis-boronic acid. For ease of isolation and to preserve the often sensitive C-B bond, all boronic acids were readily converted to their more stable trifluoroborate counterparts.
