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N ‐Methylacridinium Salts: Carbon Lewis Acids in Frustrated Lewis Pairs for σ‐Bond Activation and Catalytic Reductions
Author(s) -
Clark Ewan R.,
Ingleson Michael J.
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201406122
Subject(s) - chemistry , frustrated lewis pair , boranes , lewis acids and bases , silanes , hydrosilylation , hydride , medicinal chemistry , aldimine , catalysis , phenylsilane , reactivity (psychology) , adduct , silsesquioxane , organic chemistry , polymer chemistry , silane , boron , medicine , hydrogen , alternative medicine , pathology , polymer
N‐methylacridinium salts are Lewis acids with high hydride ion affinity but low oxophilicity. The cation forms a Lewis adduct with 4‐(N,N‐dimethylamino)pyridine but a frustrated Lewis pair (FLP) with the weaker base 2,6‐lutidine which activates H 2 , even in the presence of H 2 O. Anion effects dominate reactivity, with both solubility and rate of H 2 cleavage showing marked anion dependency. With the optimal anion, a N‐methylacridinium salt catalyzes the reductive transfer hydrogenation and hydrosilylation of aldimines through amine–boranes and silanes, respectively. Furthermore, the same salt is active for the catalytic dehydrosilylation of alcohols (primary, secondary, tertiary, and ArOH) by silanes with no observable over‐reduction to the alkanes.