Synthesis of Arylamines via Non‐Aerobic Dehydrogenation Using a Palladium/Carbon‐Ethylene System

Abstract

The reaction of cyclohexanones with amines proceeded under an ethylene atmosphere in the presence of a catalytic amount of palladium/carbon to afford a variety of arylamines in good to high yields. The present reaction was carried out under completely non-aerobic conditions, and which is in contrast with the previously reported aerobic system. has wide applicability affording a variety of aromatic amines, and coproduct of the reaction is only gaseous ethane. Thus, this method is environmentally friendly. This protocol was applied intramolecularly to provide a novel method for the construction of quinoline and isoquinoline compounds.

Stereoretentive N‐Arylation of Amino Acid Esters with Cyclohexanones Utilizing a Continuous‐Flow System

“…Although transition metal‐catalyzed N ‐arylation of amines with aryl halides is practical for synthesizing aryl amines, [17–19] it cannot be easily applied to stereoretentive reactions of amino acid esters (Scheme 1a); this N ‐arylation is limited by racemization and other side reactions from stoichiometric or excess amounts of strong base reagents [13–16] . In contrast, the catalytic N ‐arylation of amines with cyclohexanones is a promising method that can be applied to the synthesis of amino acid esters (Scheme 1b) [20–24] . Unlike transition metal‐catalyzed C−N couplings using aryl halides, this reaction proceeds under neutral conditions in the absence of base reagents and will, therefore, be compatible with base‐sensitive amino acid compounds.…”

“…[13][14][15][16] In contrast, the catalytic N-arylation of amines with cyclohexanones is a promising method that can be applied to the synthesis of amino acid esters (Scheme 1b). [20][21][22][23][24] Unlike transition metal-catalyzed CÀ N couplings using aryl halides, this reaction proceeds under neutral conditions in the absence of base reagents and will, therefore, be compatible with basesensitive amino acid compounds. Furthermore, this reaction, which consists of consecutive condensation and dehydrogenative aromatization, has several advantages over conventional CÀ N couplings: (i) small amounts of co-products such as H 2 O are easily removable, (ii) cyclohexanones bearing various functional groups can be prepared using classical synthetic methodologies as halogen-free sources of aromatic rings, and (iii) the use of heterogeneous Pd catalysts can significantly reduce the costs associated with the catalysis and the purification process.…”

Synthesis of Substituted Anilines from Cyclohexanones Using Pd/C–Ethylene System and Its Application to Indole Synthesis

“…Although there are some reports on the palladium-catalyzed synthesis of arylamines under aerobic conditions, those on the synthesis of arylamines under nonaerobic conditions are quite rare. In 2018, we reported a new synthetic method involving the reaction of cyclohexanones with primary and secondary amines in the presence of the Pd/C under ethylene atmosphere to afford secondary and tertiary arylamines, respectively . No reaction between cyclohexanone and ammonia occurred under the same conditions.…”

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.…”