Regioselectivity in the Sonogashira coupling of 4,6-dichloro-2-pyrone

The Sonogashira cross-coupling of 4,6-dichloro-2-pyrone with terminal acetylenes proceeds in good yields and high regioselectivity for the 6-position; dibenzylidene acetone (dba) type ligands play a non-innocent role in reactions mediated by Pd(dba)(2)/PPh3; theoretical studies indicate that C-6 oxidative addition is favoured both kinetically and thermodynamically

Mechanistic Elucidation of the Arylation of Non-Spectator N-Heterocyclic Carbenes at Copper using a Combined Experimental and Computational Approach

CuI(NHC)Br complexes (NHC = N-heterocyclic carbene) undergo a direct reaction with iodobenzene to give 2-arylated benzimidazolium products. The nature of the Nsubstituent on the NHC ligand influences the reactivity of the CuI(NHC)Br complex towards arylation. N-Benzyl or Nphenyl substituents facilitate arylation, whereas N-mesityl substituents hinder arylation. Density functional theory calculations show that an oxidative addition/reductive elimination pathway, involving CuIII species, is energetically feasible. A less hindered CuI(NHC)Br complex, with N-benzyl groups, is susceptible to oxidation reactions to give 1,3- dibenzylbenzimidazolium cations containing a CuIBrx anion (various polymorphs). The results described herein are of relevance to C-H functionalization of benz(azoles)

A new precatalyst for the Suzuki reaction - a pyridyl-bridged dinuclear palladium complex as a source of mono-ligated palladium(0)

A dinuclear pyridyl-bridged palladium complex, trans-(P,N)-[PdBr(μ- C5H4N-C2,N)(PPh3)]2 1, was obtained from material isolated from the Suzuki cross-coupling reaction of 2-bromopyridine with 2,4-difluorophenylboronic acid in the presence of catalytic (PPh3)4Pd. Complex 1 is an effective precatalyst for the Suzuki cross-coupling reactions of a variety organoboronic acids and aryl bromides, and represents a useful source of mono-ligated palladium(0), "(Ph3P)Pd(0)"