Cationic Nickel Complexes with Weakly Coordinating Counterions and Their Application in the Asymmetric Cycloisomerisation of 1,6‐Dienes

Abstract

The influence of the counterion on cationic nickel catalysts for asymmetric cycloisomerisation of diethyl diallylmalonate (1a) and N,N-diallyltosylamide (1b) is investigated. The activity of the catalysts formed from [Ni(h 3

Remarkable anion effects uncovered in the development of a Au(iii)-catalyzed tandem nucleophilic substitution–1,5-enyne cycloisomerization process

“…However, this anion has rarely been used in Au catalysis, but has been in other cycloisomerization processes. 17 To our delight, 90% conversion was observed in 15 min at 0 1C. Presumably a more 'naked' Au cation is produced under these conditions; under identical conditions AgOTf gives only 1% conversion!…”

Enantioselective, transition metal catalyzed cycloisomerizations

“…The same azaphospholene ligand as well as the phosphoramidite Quinaphos have been used also for the cycloisomerization of diallyltosylamide, but the enantioselectivity levels were only moderate (33-54% ee, depending on the pre-catalyst used). 78 Overall, although significant ees have been attained in some cases, the scope of the enantioselective intramolecular hydrovinylations of dienes remains rather restricted.…”

Nickel(II) N‐Heterocyclic Carbene Complexes: Versatile Catalysts for C–C, C–S and C–N Coupling Reactions

“…Transition‐metal‐catalysed coupling reactions are among the most useful tools for C–C, C–S and C–N bond formationPalladium‐based catalysts bearing phosphines and more recently, N‐heterocyclic carbene (NHC) ligands have been widely used in these transformations because they display tolerance towards a variety of functional groups and versatility in terms of reaction conditions . Numerous reports have been published regarding the use of nickel catalysts in many catalytic processes, including cross‐couplings, cycloisomerisations, cycloadditions, annulations and others . When using NHC ligands, nickel‐based catalytic systems have recently shown excellent results in a wide variety of transformations .…”