Non-phosgene processes for the synthesis of carbamates and/or substituted ureas have attracted increasing interest in recent years, particularly in the area of green chemistry because of the environmental concern regarding the use of highly toxic phosgene. [1] Of the various non-phosgene processes, one approach involves the catalytic oxidative carbonylation of an amine in the presence of an appropriate catalyst or catalytic system. [2] In previous reports, we have demonstrated that alkali metal-containing selenium compounds, obtained from the reaction of SeO 2 and M 2 CO 3 (M ΒΌ alkali metal) in methanol, are effective catalysts for the oxidative carbonylation of aniline to produce phenyl carbamate and diphenylurea. [3] The major disadvantage of using these selenium compounds is the difficulty in separating the product and the catalyst from the reaction mixture, which arises from the coproduction of insoluble diphenylurea and soluble alkyl phenyl carbamate, with high conversion of aniline. A further disadvantage is the formation of small quantities of unknown, highly volatile, malodorous, and possibly toxic selenium species at relatively high reaction temperatures.
Recently, there have been a considerable number of papers regarding ionic liquids and their use in immobilizing volatile, precious, and/or toxic homogeneous catalysts, thereby improving the stability and facilitating the recovery of the catalyst. [4] In this context, the alkali metal-containing selenium compound [KSeO 2 (OCH 3 )] can be reacted with 1-alkyl-3-methylimidazolium chlorides to prepare new imidazolium-based ionic liquids containing anionic selenium species. The ionic liquids are found to show surprisingly high activity for the ZUSCHRIFTEN 4476