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.