{"title":"Direct C–N coupling of aniline to aminodiphenylamines with a platinum-loaded titanium oxide photocatalyst†","authors":"Kexin Zou , Akira Yamamoto , Hisao Yoshida","doi":"10.1039/d4cy01413h","DOIUrl":null,"url":null,"abstract":"<div><div>Aminodiphenylamines (ADPAs) and their derivatives have been known to be used as dye intermediates and antioxidants of rubber. Due to their high demand in industrial production, their synthesis methods have been widely developed. In the present study, a photocatalytic asymmetric homocoupling route was examined, <em>i.e.</em>, the photocatalytic C–N coupling of aniline in an alkaline solution with a Pt-loaded titanium oxide (Pt/TiO<sub>2</sub>) photocatalyst. A nearly 20% yield and 77% selectivity were achieved with the Pt/TiO<sub>2</sub> photocatalyst for 30 min. It was found that this C–N bond formation showed a high dependence on the pH of the solvent and irradiation light wavelength, <em>i.e.</em>, the reaction can only proceed when pH > 11.79, and an incident light wavelength of 365 nm gave a high ADPA selectivity. The mechanistic studies by using isotopic compounds suggested that the rate-determining step (RDS) for ADPA production would be the formation of a transition complex with rehybridization to sp<sup>3</sup> on the aromatic ring of aniline. The UV-vis spectral analysis and Arrhenius plots further revealed the presence of three formation routes of ADPAs in the present system: the first one begins with the hole-oxidation of aniline by the TiO<sub>2</sub> photocatalyst excited by UV light, the second one starts with one electron transfer from the N atom in aniline to Ti in TiO<sub>2</sub>, which only occurred with an incident light wavelength of 365 nm, and the last one is the oxidation of aniline molecules by hydroxyl radicals as a minor route.</div></div>","PeriodicalId":66,"journal":{"name":"Catalysis Science & Technology","volume":"15 4","pages":"Pages 1228-1237"},"PeriodicalIF":4.4000,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Catalysis Science & Technology","FirstCategoryId":"92","ListUrlMain":"https://www.sciencedirect.com/org/science/article/pii/S2044475325000176","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Aminodiphenylamines (ADPAs) and their derivatives have been known to be used as dye intermediates and antioxidants of rubber. Due to their high demand in industrial production, their synthesis methods have been widely developed. In the present study, a photocatalytic asymmetric homocoupling route was examined, i.e., the photocatalytic C–N coupling of aniline in an alkaline solution with a Pt-loaded titanium oxide (Pt/TiO2) photocatalyst. A nearly 20% yield and 77% selectivity were achieved with the Pt/TiO2 photocatalyst for 30 min. It was found that this C–N bond formation showed a high dependence on the pH of the solvent and irradiation light wavelength, i.e., the reaction can only proceed when pH > 11.79, and an incident light wavelength of 365 nm gave a high ADPA selectivity. The mechanistic studies by using isotopic compounds suggested that the rate-determining step (RDS) for ADPA production would be the formation of a transition complex with rehybridization to sp3 on the aromatic ring of aniline. The UV-vis spectral analysis and Arrhenius plots further revealed the presence of three formation routes of ADPAs in the present system: the first one begins with the hole-oxidation of aniline by the TiO2 photocatalyst excited by UV light, the second one starts with one electron transfer from the N atom in aniline to Ti in TiO2, which only occurred with an incident light wavelength of 365 nm, and the last one is the oxidation of aniline molecules by hydroxyl radicals as a minor route.
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