Synthesis and Structures of Arene Ruthenium (II) –NHC Complexes: Efficient Catalytic α‐alkylation of ketones via Hydrogen Auto Transfer Reaction

The new arene Ru (II) ‐NHC complexes were synthesised and characterized. They were effectively employed as borrowing hydrogen catalysts for the construction of new C‐C and C‐N bonds from the coupling reaction of ketones and primary alcohols to desired α‐alkylated ketones and quinoline products with good to excel lent yield of 84–96%. A panel of six new arene Ru (II) ‐NHC complexes2a ‐f, (NHC  = 1,3‐diethyl‐(5,6‐dimethyl)benzimidazolin‐2‐ylidene1a, 1,3 ‐dicyclohexylmethyl‐(5,6‐dimethyl)benzimidazolin‐2‐ylidene1b and 1,3 ‐dibenzyl‐(5,6‐dimethyl)benzimidazolin‐2‐ylidene1c) were synthesized from the transmetallation reaction of Ag ‐NHC with [(η6‐arene)RuCl2]2 and characterized. The ruthenium (II) ‐NHC complexes2a ‐f were developed as effective catalysts for α‐alkylation of ketones and synthesis of bioactive quinoline using primary/amino alcohols as coupling partners respectively. The reactions were performed with 0.5 mol% catalyst load in 8 h under aerobic condition and the maximum yield was up to 96%. Besides, the different alkyl wingtips on NHC and arene moieties were studied to differentiate the catalytic robustness of the complexes in the transformations.

Source: Applied Organometallic Chemistry - November 19, 2018 Category: Chemistry Authors: Gunasekaran Balamurugan, Sundarraman Balaji, Rengan Ramesh, Nattamai S.P. Bhuvanesh Tags: FULL PAPER Source Type: research