Diazapolycyclic compounds. XX. Stereochemistry of some addition reactions to the double bond at the terminal tetrahydropyridazine ring of methyl substituted 4a,12a-diaza-1,4,4a,5,12,12a- and 4a,12a-diaza-3,4,4a,5,12,12a-hexahydronaphthacene-5,12-diones,and the corresponding epoxides

The stereochemistry of N-bromosuccinimide electrophilic additions to the double bond at the terminal tetrahydropyridazine ring moiety of the 4a,12a-diazatetracyclic compounds 1-4 has been studied. These reactions appear as very regio- and stereoselective. Most the of the results obtained support the hypothesis that the N-bromoamide additions to cyclohexenes and heterocyclic analogous do not occur via the usual Ad_E2 mechanism, because the nucleophilic step is the rate-limiting one and the main product-determining factor. On the other hand, epoxidation of the double bond in 1-4 and further opening of the oxirane ring take place in accordance with the normal stereochemical rules.