The effect of benzannelation on the equilibrium conformation and flexibility of the dihydrocycle in cyelohexa-l,4-dienone, para-quinone, and their imino and methylene analogs was studied by the semiempirical quantum-chemical AM1 method. The equilibrium conformations of the carbonyl derivatives are planar. In the imino-and methylenesubstituted analogs, the dihydrocycle adopts a boat conformation due to repulsions between the hydrogen atoms at the exocyclic double bond and in the peri positions of the benzene rings. Annelation of cyclohexa-2,5-dien-l-one and para-quinone with benzene rings at the C=C double bonds causes an increase in the conformational flexibility of the partially hydrogenated ring owing to an increase in the bending strain in the first compound and a decrease in the conjugation between the carbonyl groups and the remaining part of the molecule in the second compound.
The mteraction of 1,3-diaminopropane with gtyoxal and NaOCI in water at pH 9.5-10.5 afforded the previously unknown 6,6"-big(|,5-dtazabicyclo[3.1.0]hexane). According to X-ray diffraction data, both bicycltc fragments of the title compound adopt a tx~at conformation.
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