CATALYTIC ACTIVITY OF VARIOUS SALTS IN THE REACTION OF 2,3-EPOXYPROPYL PHENYL ETHER AND CARBON-DIOXIDE UNDER ATMOSPHERIC-PRESSURE

Reaction of 2,3-epoxypropyl phenyl ether (1) with carbon dioxide was carried out under atmospheric pressure in N-methylpyrrolidinone (NMP) at 100-degrees-C in the presence of 5 mol % of various salts to obtain a five-membered cycliccarbonate, 4-(phenoxymethyl)-1,3-dioxolan-2-one(2), selectively. Only halide salts showed high catalytic activity, and the order of intrinsic activity was found to be as follows: chloride > bromide > iodide which is the order of nucleophilicity of the anion. Furthermore, the order of the activity was found to be lithium salt > sodium salt > benzyltrimethylammonium salt, which is in accord with the order of Lewis acidity of the cation. Kinetic analyses show that the reaction rate can be represented by -d[1]/dt=k[1][cat.], where the carbon dioxide pressure shows no effect on the reaction rate. The reaction proceeds via nucleophilic attack of halide to oxirane to form beta-haloalkoxide 4 which reacts with CO2 followed by cyclization. The presence of key intermediate 4 was indirectly proved by the reaction of 1 with 1 equiv of LiBr in the absence of CO2 at 100-degrees-C for 2.5 h in NMP which leads to 1-phenoxy-2-propanone (6) in 20 % yield as the rearrangement product of 4.