Experimental and theoretical investigation of reaction of aniline with dimethyl carbonate catalyzed by acid–base bifunctional ionic liquids

Acid–base bifunctioanal ionic liquid, 1-(2-(1′-piperidinyl) ethyl)-3-methyl imidazolium trichlorolead ([PEmim]PbCl3), is an efficient catalyst for the reaction of aniline and dimethyl carbonate (DMC). The [PEmim]PbCl3 catalyzed reaction gives methyl-N-methyl-N-phenylcarbamate in the yield of 72%, while the basic ionic liquid, 1-(2-(1′-piperidinyl) ethyl)-3-methyl imidazolium chloride, and the acidic PbCl2 give the yields of 47% and 6%, respectively. The high reactivity of [PEmim]PbCl3 is accounted for its ability to activate both aniline and DMC by the acidic and basic sites cooperatively. Density functional theory (DFT) calculations simulate the structures and charge properties of [PEmim]PbCl3, complex of [PEmim]PbCl3 and aniline, and complex of [PEmim]PbCl3 and DMC. The calculations show that [PEmim]PbCl3 can increase the electrophilicity of DMC and the nucleophilicity of aniline by its acid and base sites.