Selective N-acetylation with concurrent S-oxidation of o-amino thiol at ambient conditions over Ce doped ZnO composite nanocrystallites

• Published in: Molecular catalysis 2018-05, Vol.450, p.19-28
• Main Authors: Jagtap, Rohidas, Sakate, Sachin, Pardeshi, Satish
• Format: Article
• Language: English
• Subjects: Ce doped ZnO nanospheres; Lewis acid sites; N-acetylation and S-oxidation; o-amino thiol; Substrate scope
• ISSN: 2468-8231; 2468-8231
• DOI: 10.1016/j.mcat.2018.03.007

[Display omitted] •Synthesis and characterization of pure and Ce doped ZnO composite nanocrystallites.•The XRD support to formation of doped and composite materials.•Dual concurrent transformation of o-amino thiol.•Enhanced selectively for N-acetylated SS coupled product.•Delayed desorption of S from more Lewis acidic centers favored concurrent oxidation. The oxidative SS coupling of thiol to disulfide is an imperative chemical transformation in the domain of biological processes and also finds numerous chemical applications. The CeO2 and ZnO are significant catalysts for oxidation of thiol to disulfide and N-acetylation of amines respectively. Dithiobis(phenylene)bis(benzyldeneimine) moiety containing N-acetyl and disulfide functional groups is a potential antimicrobial agent with Leishmanicidal and antihyperlipidemic activities. Herein, we report a synchronized catalytic application of Ce doped ZnO (Ce-ZnO) and CeO2-Ce-ZnO composites for selective synthesis of Dithiobis(phenylene)bis(benzyldeneimine) from o-amino thiol. The Ce-ZnO samples were synthesized by simple co precipitation method by calcination of hydroxide precursors at 400 °C to get 0–10% Ce-ZnO nanocrystallites. The formation of CeO2-Ce-ZnO composite material was observed beyond 1.5% Ce concentration. The synthesized materials were well characterized by IR, XRD, DRS spectroscopy and SEM-EDS analysis. The application of Ce doped ZnO as an efficient catalyst towards the selective N-acetylation and concurrent S-oxidation of o-amino thiol to afford Dithiobis(phenylene)bis(benzyldeneimine) at ambient temperature in acetonitrile was deliberated. Among all screened catalysts, the maximum selectivity was found for 7.5% Ce-ZnO as CeO2-Ce-ZnO composite catalyst. Lewis acidic property of catalyst supported probable mechanism for achieved dual transformations. Also, the 7.5% Ce-ZnO catalyst has demonstrated a versatile SS coupling ability for variety of thiol substrates with excellent stability.