abstract
Using MeOH as the methylating agent, selective methylation of secondary alcohols and nitroaromatics is achieved using a newly prepared Ru(II)-catalyst 1a of a tridentate azo-aromatic ligand. Two new organometallic Ru(II)-complexes [Ru(Cp)(PPh3)(L a )]Cl (1a) and [Ru(Cp)(PPh3)(L b )]Cl (1b) of tridentate redox-active ligands 2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline (L a ) and 2-(phenyldiazenyl)-1,10-phenanthroline (L b ) were prepared and characterized by different spectroscopic methods. 1a and 1b demonstrated good catalytic activity in the methylation of a diverse array of 1-aryl ethanols and nitroarenes. 1a showed encouraging catalytic efficiency with various naturally occurring steroids, including 4-cholestene-3-one, progesterone, estrone, and beta-sitosterol, highlighting its capability to modify natural product scaffolds. Mechanistic studies revealed that 1a-catalyzed methylation reactions advance through a hydrogen borrowing pathway involving cooperative participation of both Ru(II) and the aryl azo scaffold.
keywords
ALPHA-ALKYLATION; BORROWING HYDROGEN; BETA-ALKYLATION; BOND FORMATION; KETONES; AMINES; MONOMETHYLATION; NITROARENES; STRATEGY; ROUTE
subject category
Chemistry
authors
Chakraborty, S; Khanra, S; Dutta, S; Branda, P; Paul, ND
our authors
Paula Cristina Ferreira da Silva Brandão
Assistant ResearcherProjects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
acknowledgements
The research was funded by DST-SERB (project: CRG/2023/003413) and MoE STARS, Govt. of India (project STARS2/2023-0450). S.C. and S.K. are grateful to IIESTS for fellowship support. We acknowledge the financial assistance from IIESTS and thank DST for sponsoring SAIF. IIESTS is also acknowledged for providing HRMS and NMR facilities. P.B.similar to gratefully acknowledges the financial support of this work by the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC).