抄録
7-Mono- and 7, 7-disubstituted 5-ethoxycarbonyl-1-phenyl-2-azabicyclo[3.2.0]heptane-3, 4-diones undergo epimerization at C-7 when treated when treated with base. Experiments using the stereospecifically deuterium labeled compound 6 showed that the inversion of stereochemistries at C-6 and C-7 took place simutaneously in this reaction, thus proving that the reaction proceeded through C1-C5 bond fission and recyclization. The suggested intermediate 10 with a highly strained seven membered ring would give either the C7 epimerized product by a fast recombination or irreversibly give the dihydroazatropolones 9 by a trans- to cis- isomerization of the C=N double bond. Kinetic treatments showed that the latter reaction is slower than the former equilibrium reaction.The analogous 7-epimerization reaction observed in the hydride reduction of the 4-oxo group and in the photolysis of the imidate 24 was proved to proceed with a similar mechanism.
