Efficient methylation of anilines with methanol catalysed by cyclometalated ruthenium complexes

Abstract

Cyclometalated ruthenium allow the effective and selective N-methylation of anilines under mild conditions.

Cyclometalated (NNC)Ru(ii) complex catalyzed β-methylation of alcohols using methanol

“…3–7 Among them cyclometalated tridentate and bidentate Ru( ii ) complexes have gained significant attention towards catalyzing various hydrogen transfer reactions. 8–24 Earlier the Baratta and Yu groups developed unsymmetrical (NNC)Ru( ii ) complexes which showed high catalytic activity towards the transfer hydrogenation of ketones in isopropanol. 13,17,25,26 Later on, cyclometalated (NC)Ru( ii ) complexes were developed by the Chen group and applied towards the acceptorless dehydrogenation of primary alcohols to carboxylic acids, the α-alkylation of unactivated amides and esters and the semihydrogenation of internal alkynes to E -alkenes.…”

Borrowing Hydrogen Amination Reactions: A Complex Analysis of Trends and Correlations of the Various Reaction Parameters

“…A tabular comparison of the reaction conditions of the target process is provided in the SI (Table S8). The literature cited includes refs , , , , , − , , − , , , − , , , , , , , − , , , , − , , − , , , ,, − , , − , − , − , ,, , , , , , , , , , , − , , , and − . At the end of this block, diagrams are presented, which show the correlations between bases and temperatures (Figure ), and between bases and metal-based catalysts (Figure ) used in this process.…”

Catalysis with cycloruthenated complexes

“…Recently, Beller and co-workers applied cyclometallated imidazoline ruthenium complexes in the N -methylation of several aromatic anilines ( Scheme 44 ). 77 This transformation has literature precedent with other catalysts; however, the use of a cyclometallated ruthenium complex allows milder conditions and a less expensive base to be used. Although steric bulk in the ortho -position of the aromatic aniline was poorly tolerated, the reaction proceeded with meta - and para -substituents.…”