The Ullmann Synthesis of Biaryls, 1945-1963

Carboxylate‐Based, Room‐Temperature Ionic Liquids as Efficient Media for Palladium‐Catalyzed Homocoupling and Sonogashira–Hagihara Reactions of Aryl Halides

“…In addition, many functionalized biaryls cannot be obtained under such drastic conditions. [3] As a result, different catalysts, including nickel, [4] barium, [5] indium, [6] zinc, [7] and palladium, [8] have been used to promote the homocoupling of haloarenes. Of all the metals used, palladium-catalyzed homocoupling of aromatic halides is remarkably effectual to afford high product yields.…”

Palladium catalyzed reductive homocoupling reactions of aromatic halides in dimethyl sulfoxide (DMSO) solution

“…The copper-mediated Ullmann reductive coupling reactions of aromatic halides have been traditionally used to synthesize symmetrical biaryls for over one century [4,5], but these reactions require both high temperature (over 200°C) and the consumption of a stoichiometric amount of copper. As a result, many functional groups cannot survive such drastic reaction conditions and have had very limited applications in synthesizing the highly functionalized biaryls [6,7].…”

Hypervalent iodine compounds derived from o-nitroiodobenzene and related compounds: syntheses and structures

“…Abnormally high reactivity of o-nitrohaloarenes compared to p-substituted ones in a number of reactions, such as Ullmann coupling 1 , Cu(I) catalysed substitution of one halogen by another 2 , dehalogenation with Cu in boiling acetic acid 3 , has no clear explanation in the literature. We supposed that the enhanced reactivity of o-nitrohaloarenes could be a result of formation of a strong hypervalent donor-acceptor bond between oxygen of a nitro group and a halogen atom in a transition state or in an intermediate.…”