화학공학소재연구정보센터
Catalysis Letters, Vol.146, No.8, 1517-1528, 2016
Tin-Catalyzed Urea Alcoholysis With beta-Citronellol: A Simple and Selective Synthesis of Carbamates
Tin(II) chloride is a stable and water tolerant Lewis acid, commercially available and less corrosive than Bronsted acid catalysts. Our proposal was demonstrated that SnCl2 was an efficient catalyst on the urea alcoholysis with beta-citronellol. We investigated the effects of main reaction parameters such as concentration and tin(II) catalyst nature, reagents stoichiometry and reaction temperature. In homogenous conditions with DMSO as solvent, the SnCl2-catalyzed urea alcoholysis reactions under air flux achieved high conversion and selectivity for beta-citronellyl carbamate (ca. 90 and 95 %, respectively). Among tin(II) catalysts assessed, SnCl2 was more active due to its total solubility. Possible intermediates of active Sn(II) species were discussed based on the results of catalytic runs and FT-IR spectroscopy measurements of the liquid phase after the reaction. FT-IR spectroscopy data showed that the active species could be a complex of a Sn(II) atom coordinated with N=C=O. This novel and phosgene-free selective process provide an inexpensive and attractive route to synthesize terpenic carbamates through inexpensive and renewable reactant (i.e. urea). Moreover, SnCl2 was also an efficient catalyst on synthesis of beta-citronellyl carbonate. [GRAPHICS]