Nickel-Catalyzed Amination of Aryl Thioethers: A Combined Synthetic and Mechanistic Study

Abstract

dicyclohexylphosphino)ethane (dcype) complex for the catalytic Buchwald−Hartwig amination of aryl thioethers. The protocol shows broad applicability with a variety of different functional groups tolerated under the catalytic conditions. Extensive organometallic and kinetic studies support a nickel(0)−nickel(II) pathway for this transformation and revealed the oxidative addition complex as the resting state of the catalytic cycle. All the isolated intermediates have proven to be catalytically and kinetically competent catalysts for this transformation. The fleeting transmetalation intermediate has been successfully synthesized through an alternative synthetic organometallic pathway at lower temperature, allowing for in situ NMR study of the C−N bond reductive elimination step. This study addresses key factors governing the mechanism of the nickel-catalyzed Buchwald−Hartwig amination process, thus improving the understanding of this important class of reactions.

On the NH and CH acidities of toluidine isomers: theoretical description and practical consequences for the synthesis of certain aniline dyes

“…For example, the acidity constant of the positively charged anilinium ion p K a ( ANH 3 + ) in DMSO is 3.8 26,29 . Aniline is also a weak acid that can only be deprotonated by very strong bases (eg, lithium organyl compounds) 30‐32 . The experimental p K a for the heterolytic dissociation of aniline to the deprotonated anion ( ANH − ) in DMSO is 30.6 14 .…”

Preparation of Recyclable and Versatile Porous Poly-Arylthioethers by Reversible Pd-Catalysed C–S/C–S Metathesis

“…This observation points towards transmetallation as the rate-determining-step on the reaction. 34 To demonstrate the importance of the reaction's reversibility for the synthesis of the materials, an alternative synthesis of the material P1 was attempted following the most common procedure to prepare sulphur-based polymers: polycondensation reaction of aryl halides with Na2S at elevated temperatures (250 °C). The material P1' was indeed obtained according to the FT-IR spectra (Figure S22), albeit in considerably lower yield than P1 (35% vs. 88%, Figure 1e) and, more importantly, P1' was non-porous (<5 m 2 •g -1 vs 192 m 2 •g -1 for P1), indicative of an amorphous, interlinked polymer formed under complete kinetic control.…”

Theoretical study of NH and CH acidities of toluidine isomers – dependence on their oxidation states

“…Aniline is also a weak acid which can be deprotonated only by very strong bases, e.g. by lithium organyl compounds [13]. The available experimental pKa for heterolytic dissociation of aniline to deprotonated anion (ANH -) in DMSO is 30.6 [14].…”