Suzuki nickel-catalysed

A variety of oxetanes are available commercially, and finding appropriate handles (amines, acids, alcohol, etc.) is not difficult. Traditional methods of oxetane synthesis, such as Williamson ether synthesis and [2 + 2] cycloadditions, have been extensively reviewed. Of more interest in the rapid expansion of a monomer collection is the functionalisation of simple oxetanes. For example, atyl oxetanes have been prepared by the nickel catalysed Suzuki coupling of 3-iodooxetane (Scheme 18.20). ... 

A detailed study using X-ray crystallography, H, C, and P NMR (nuclear magnetic resonance) spectroscopies, product studies, a secondary a-deuterium KIE (kinetic isotope effect) of 1.13, competition experiments, and a stereochemical study has shown that the nickel-catalysed Suzuki reaction of N,0 acetals with (PhBO)3, and a DPEPhos ligand occurs by the 6 1-like mechanism shown in Scheme 1. 

The three basic steps in the palladium-catalysed Suzuki-Miyaura reaction involve oxidative addition, transmetalation, and reductive elimination. A systematic study of the transmetalation step has found that the major process involves the reaction of a palladium hydroxo complex with boronic acid, path B in Scheme 3, rather than the reaction of a palladium halide complex with trihydroxyborate, path A. A kinetic study using electrochemical techniques of Suzuki—Miyaura reactions in DMF has also emphasized the important function of hydroxide ions. These ions favour reaction by forming the reactive palladium hydroxo complex and also by promoting reductive elimination. However, their role is a compromise as they disfavour reaction by forming of unreactive anionic trihydroxyborate. A method for coupling arylboronic acids with aryl sulfonates or halides has been developed using a nickel-naphthyl complex as a pre-catalyst. It works at room temperature in toluene solvent in the presence of water and potassium carbonate. ... 

Han has comprehensively reviewed the use of nickel catalysts for the Suzuki-Miyaura cross-coupling reaction/ and found that the nickel mediated process can tolerate a broad range of aryl electrophiles, for example, sulfamates, carbamates, carboxylates, ethers, carbonates, phosphoramides, phosphonium salts, phosphates, phenols, and a broad range of alkyl substrates including both secondary and primary alkyl iodides, bromides, and chlorides. Many of these electrophiles have been found to be incompatible with traditional palladium catalysed processes. 

Extending their process in this field, Zhou and Fu in 2004 developed the first Suzuki coupling of unactivated secondary alkyl bromides and iodides catalysed by nickel. " In 2008, Saito and Fu discovered that the combination of Ni(cod)2 with chiral ligand (Scheme 3.16) could be used to couple... 

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