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Studies of 2-Oxazolidinones. III. Kinetics of the Pyrolytic Decarboxylation of 2-Oxazolidinones

1962; Oxford University Press; Volume: 35; Issue: 12 Linguagem: Inglês

10.1246/bcsj.35.1915

1348-0634

Ryohei Oda, Masahiko Miyanoki, Masaya Okano,

Chemical Reactions and Mechanisms

Abstract The kinetics of the pyrolytic decarboxylation of 3-substituted 2-oxazolidinones have been studied and the following results obtained. (1) This decomposition is an autocatalytic reaction, in which the amine formed acts as a catalyst. (2) In the decarboxylation of 3-aryl-2-oxazolidinones, the electronic effect of the substituent on the benzene ring indicates that the fission of the N–C bond of the urethane group in the 2-oxazolidinone ring is rate-determining. (3) The initial rate of the aliphatic amine-catalyzed decarboxylation of 3-aryl-2-oxazolidinones is of the pseudo-first-order; it also depends on the concentration and structure of the amine. A mechanism has been proposed which involves a nucleophilic attack of amine on the carbonyl-carbon atom. An amine having an hydroxyl or amino group on the β-carbon shows a large rate-acceleration; this suggests the simultaneous electrophilic participation by the active hydrogen of these groups. (4) The initial rate of the decarboxylation of 2-oxazolidinone itself, catalyzed by aliphatic amine, is of the second-order in oxazolidinone and of the first-order in amine. From this a concerted mechanism has been inferred, in which the amine acts as a nucleophile and the other oxazolidinone acts as an electrophile.