Aryl−Aryl Bond Formation One Century after the Discovery of the Ullmann Reaction

Triazolopyridines. Part 29. Direct arylation reactions with [1,2,3]triazolo[1,5-a]pyridines

“…18 The formation of the biaryl derivative 5 can be explained by a homocouplig reaction of 2. 19 Several attempts to improve these results have been made modifying the reaction conditions. We modified the reaction time and temperature (Table 1, entry 2), the ligand and reaction time (entries 3 20 -5), the catalyst (entry 6), yet we always obtained mixtures of difficult handling and unfavourable results.…”

Beyond Traditional Cross Couplings: The Scope of the Cross Dehydrogenative Coupling Reaction

“…[41] These couplings have been dogged by slow reaction rates, low yields/conversions, and poor regioselectivities, often giving complex mixtures of products. [42][43][44] However, successful couplings of several biaryls to yield the cross-coupled products catalyzed by Pd II salts in the presence of a variety of oxidants has been reported.…”

Bidirectional Metalation of Hydrobenzoin: Direct Access to New Chiral Ligands and Auxiliaries

“…While there are many examples of biaryl couplings, including the Ullmann (copper-catalyzed), Stille, and Suzuki reactions (palladium-catalyzed) and the Suzuki reaction (palladium-catalyzed), 72 our initial efforts focused on identifying a suitable copper reagent that would promote the oxidative coupling of the lithium tetraanion as described in Scheme 55. Also, based on the precedent established by Furstner for the iron-catalyzed cross-coupling of sp 2 hybridized magnesium carbanions, 73 and Negishi for the homo-coupling of sp 2 and sp 3 lithium carbanions using stoichiometric palladium, the reported conditions for these couplings were repeated with tetraanion 142 as indicated in Table 17.…”