New Ring Opening Reactions of Oxiranes with Aryl Carboxylates

Abstract Oxiranes reacted with aryl esters in the presence of base. The reactions of aryl carboxylates with alkyloxiranes afforded almost exclusively 1-alkyl-2-(aryloxy) ethyl carboxylates, whereas the reactions with aryloxiranes gave a mixture of 1-aryl-2-(aryloxy) ethyl carboxylates and 2-aryl-2-(aryloxy) ethyl carboxylates. Similar results were also obtained in the reaction with S-aryl thiocarboxylates and diaryl carbonates. The rate of reaction between phenyl acetate and phenoxymethyloxirane (PMO) in the presence of tributylamine (n-Bu3N) as a catalyst has been determined in the temperature range 110 to 130 °C and may be expressed by –d[PMO]⁄dt=k2[n-Bu3N]·[PMO]. The apparent activation energy calculated from the Arrhenius plots is 85.8 kj/mol. The reaction catalyzed by tributylamine is assumed to proceed through zwitter ions, n-Bu3\overset+NCH2CH(R)O− and n-Bu3\overset+NCH(R)CH2O−, which attack aryl carboxylate.