Transition‐Metal‐Free N‐Arylation of Amines by Triarylsulfonium Triflates

Abstract

A simple and efficient method for transition-metal-free N-arylation of various amines by triarylsulfonium triflates is described. Both aliphatic and aromatic amines were smoothly converted at 80 °C in the presence of tBuOK or KOH to give the corresponding mono N-arylated products in good to high yields. The molar ratios of the reactants and the choice of bases had a big effect on the reaction. When a large excess of [Ph S][OTf] and tBuOK were employed for primary amines under the standard conditions, the bis(N-phenyl) products were predominantly formed. This method was also applicable to the synthesis of bioactive N-phenyl amino acid derivatives. The control experiments, the deuterium labelling study, and the presence of regioisomers of N-arylated products when using 4-substituted triarylsulfonium triflates suggested that the reaction might proceed through an aryne intermediate. The present protocol demonstrated that triarylsulfonium salts are versatile arylation reagents in the construction of C -N bonds.

Base‐Mediated O‐Arylation of Alcohols and Phenols by Triarylsulfonium Triflates

“…In the previous alkali‐initiated decomposition of triarylsulfonium salts, three possible mechanisms have been documented in the literatures: a S N Ar mechanism, a benzyne intermediate, and a radical process. In our recent work, the aryne species have proved to be the major reactive intermediates in transition‐metal‐free N ‐arylation of amines by triarylsulfonium triflates in the presence of t BuOK or KOH . However, in this work the investigations revealed that the aryne intermediates might not be involved in the base‐mediated O‐arylation of alcohols and phenols by triarylsulfonium triflates.…”

“…The less effective production of 3 u and 3 y in the presence of CsOH might be attributed to the relatively poorer acidity of the starting alcohols as well as their steric hindrance, which required stronger base such as NaH for the conversion. Since the free NH 2 groups could be arylated by [Ar 3 S][OTf] in the presence of bases, the reaction of ethanolamine ( 1 z ) with 2 a (1.5 or 3 equiv) and CsOH (1.5 or 3 equiv) under the standard conditions formed bis(arylated) product 3 z in 22 % or 56 % yield, respectively, accompanied by a trace amount or 19 % of tri(arylated) product ( N‐( 2‐phenoxyethyl)diphenylamine, 3 z′ ). Notably, when 1,3‐butanediol ( 1 aa ) reacted with 2 a /CsOH at 50 °C for 24 h, 4‐phenoxy‐2‐butanol ( 3 aa ) was formed in 88 % yield with the secondary hydroxyl group unchanged, suggesting that the O‐phenylation could selectively occur at the primary alcoholic‐OH site.…”

Preparation, Characterization and Application of Copper Schiff base Complex Supported on MCM‐41 as a Recyclable Catalyst for the Ullmann‐type N‐arylation Reaction

“…The transition‐metal‐catalyzed C−N bond formation, known as N‐arylation reaction, has attracted much attention in organic synthesis. It is one of the most useful methods for the construction of N‐aryl amines, which constitute important structural units in various biologically active pharmaceutical ingredients and natural products . The most promising method in the literature for the N‐arylation reaction is Copper‐catalyzed Ullmann‐type transformation.…”

Direct Synthesis of Diphenylamines from Phenols and Ammonium Formate Catalyzed by Palladium

“…Diphenylamine (DPA) is primarily used as astabilizer for nitrocellulose explosives [1] and the detection of oxidizers, [2] whereas C-alkylated diphenylamines are widely used as antioxidants for the preservation of fruits, [3] oils, [4] and polymers. In addition, other methods, including P III /P V =Oc atalysis, [15] iodine, [16] sulfonium triflates, [17] various nanoparticle catalysts, [18] and Pd/C catalysis for the formationo fa rylamines from aliphatic substrates, [19] have also been reported. [7] Additionally,t riphenylamines are important for the preparation of optoelectronic materials.…”

“…[10] Arylamines are commonly prepared from amine precursors through metal-catalyzedC ÀNc oupling reactions. In addition, other methods, including P III /P V =Oc atalysis, [15] iodine, [16] sulfonium triflates, [17] various nanoparticle catalysts, [18] and Pd/C catalysis for the formationo fa rylamines from aliphatic substrates, [19] have also been reported. In addition, other methods, including P III /P V =Oc atalysis, [15] iodine, [16] sulfonium triflates, [17] various nanoparticle catalysts, [18] and Pd/C catalysis for the formationo fa rylamines from aliphatic substrates, [19] have also been reported.…”