Stoichiometric reduction of primary alkyl monohalides with electrogenerated nickel(I) salen: Formation of aldehydes

Catalytic Reduction of Phenyl‐Conjugated Acetylenic Halides by Nickel(I) Salen: Cyclization versus Coupling

“…Another feature of the cyclic voltammograms (Figures 2 and 3) is that the cathodic peak currents do not increase in proportion to the concentration of added substrate. This latter behavior, seen in a number of earlier studies, [18,19,[23][24][25] has been linked to sluggish regeneration of the precursor of the active catalyst. In at least some instances, evidence was obtained to suggest that this loss in catalytic efficiency of the nickel(II) salennickel(I) salen system may be caused by alkylation of the imino (C=N) bonds of the ligand by an alkyl radical derived from the reductive cleavage of a carbon-halogen bond of a substrate.…”

Stoichiometric reduction of secondary alkyl monohalides by electrogenerated nickel(I) salen in the presence of oxygen and water: Prospects for the formation of ketones

“…Recently, we prepared an aldehyde (1-octanal) in up to 74% yield via the reductive cleavage of a primary alkyl monohalide (1-bromooctane) by electrogenerated nickel(I) salen in dimethylformamide (DMF) containing 0.10 M tetramethylammonium tetrafluoroborate (TMABF 4 ) and in the presence of oxygen (O 2 ), water, and ultraviolet-visible light [1,2]. This result was interesting because the parent alkyl halide and the aldehyde product possess the same number of carbon atoms.…”

“…Because of our earlier findings [1,2], it seemed worthwhile to investigate whether the reaction of nickel(I) salen with a secondary alkyl monohalide might afford a ketone. We are not aware of any previous publications that involve efforts to synthesize a ketone by means of this strategy.…”

“…In addition, since water deliberately added to a nickel(II) salen-primary alkyl monohalide system enhances the formation of an aldehyde [1,2], the effects of water and other proton donors (acetic acid and 1,1,1,3,3,3-hexafluoro-2-propanol) on the interactions of nickel(I) salen with secondary alkyl monohalides have been probed.…”

Catalytic reduction of 4,4′-(2,2,2-trichloroethane-1,1-diyl)bis(methoxybenzene) (methoxychlor) with nickel(I) salen electrogenerated at reticulated vitreous carbon cathodes

“…However, when one considers the catalytic reduction of methoxychlor, there is a distinct advantage to the use of electrogenerated nickel(I) salen [22]; the latter is not air-sensitive, which makes it more stable and easier to use than cobalt (I) salen. In previous research conducted in our laboratory, electrogenerated nickel(I) salen has been successfully employed for the catalytic dehalogenation of numerous organic species [23][24][25][26][27][28][29][30][31][32][33][34][35][36]. Most relevant to the present work is an earlier investigation [22] that utilized nickel(I) salen, electrogenerated at a reticulated vitreous carbon cathode, for the catalytic conversion of DDT to 4,4ʹ-(ethene-1,1-diyl)bis (chlorobenzene).…”