Preparation
A 160 mL Parr autoclave was charged with butanol 982 (2.22 g, 0.03 mol), N-cyclohexyl-N',N',N'',N''-tetramethylguanidine (CyTMG; 6.9 g, 0.035 mol), and acetonitrile (30 mL). The autoclave was attached to a pressure head, and 160 psig CO2 was introduced with stirring at room temperature. An exothermic reaction ensued, leading to an increase in temperature to ca. 40℃. In a Fischer–Porter bottle was placed a solution of 1-chlorobutane (8.33 g, 0.09 mol) in acetonitrile (10 mL). This bottle was attached to a pressure head, and 80 psig CO2 was introduced above the solution. After 1 h, the solution of 1-chlorobutane was added in one portion under 80 psig CO2 to the pre-formed carbonate anion solution generated in the autoclave. After the addition, the pressure was increased to 160 psig with CO2, and the reaction mixture was warmed to 85 ℃ for 16 h. Thereafter, the reaction mixture was allowed to cool to room temperature, and then the pressure was released. An aliquot was removed, diluted with diethyl ether, and CyTMGH+Cl- was filtered off; by GC analysis using biphenyl as an internal standard, the yield of dibutyl carbonate was calculated as 73%; oil.
