Crown ether complex cation ionic liquids: preparation and applications in organic reactions

A series of crown ether complex cation ionic liquids (CECILs) were designed, synthesised and characterised by NMR spectroscopy, HRMS, thermogravimetric differential thermal analysis (TG-DTA) and elemental analysis. Their applications in various organic reactions were investigated: 15-C-5Na]OH], 15-C-5Na]OAc], 18-C-6K]OH] and 18-C-6K]OAc] (15-C-5=15]crown-5; 18-C-6=18]crown-6) efficiently catalysed the Michael addition of alkenes and relevant nucleophiles; 18-C-6K]OH] and 15-C-5Na]OH] effectively catalysed the Henry reaction of nitromethane and aromatic aldehydes; 18-C-6K]OH] has excellent catalytic efficiency for Knoevenagel condensation of aromatic aldehydes and malononitrile; PdCl(2) /18-C-6K](3)PO(4)]/K(2)CO(3) efficaciously catalysed the Heck reaction of olefins and aromatic halides; 18-C-6K]BrO(3)] can be used as both oxidant and solvent in the oxidation reaction of aromatic alcohols. The CECIL catalysts 15-C-5Na]OH] (Michael addition) and 18-C-6K]OH] (Henry reaction) can be recycled and reused several times without obvious loss of activity and their recovery is very simple.