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Diazapolycyclic compounds. XVI. Nmr stereochemical studies on the acid‐catalyzed oxirane ring‐opening reactions of unsubstituted, 2‐methyland 2,3‐dimethyl‐ substituted 2,3‐epoxy‐4a,12a‐diaza‐1,2,3,4,4a,5,12,12a‐octahydronaphthacene‐5,12‐diones

1979; Wiley; Volume: 16; Issue: 5 Linguagem: Inglês

10.1002/jhet.5570160540

1943-5193

F. G. CONTRERAS, Pablo Navarro,

Organic Chemistry Cycloaddition Reactions

Abstract Addition reactions in acidic media have been performed on the oxirane ring of unsubstituted, 2‐methyl‐ and 2,3‐dimethyl‐ substituted 2,3‐epoxy‐4a,12a‐diaza‐1,2,3,4,4a,5,12,12a‐octahydronaphthacene‐5,12‐diones. These reactions proceed in a stereospecific way; the Furst‐Plattner rule of 1,2‐ trans ‐diaxial ring‐opening is obeyed as can be deduced from the nmr stereochemical study on the terminal piperidazine‐ring moiety of the addition products. Acylation shift effects and 1,3‐ syn ‐diaxial interactions have been utilized to assist stereochemical assignments. The geometry of the ring corresponds in most cases to a chair slightly distorted by the sp 2 ‐sp 3 character of the nitrogens. Some of the less highly substituted among the cleavage products show certain peculiarities in their spectra, and are presumed to be in conformational equilibrium.