STERIC REQUIREMENTS AND HIGH-PRESSURE INFLUENCE ON THE THERMAL DEOXYGENATION OF N-OXIDES OF ORELLANINE-LIKE STRUCTURE

5-Hydroxy-9,10-dihydro-4-azaphenanthrene-N-oxide (1) and its methyl et her (2) were found to undergo the facile thermally induced N-oxide oxy gen elimination characteristic for the orellanine-like structures. The relationship between the conformation of the N-oxides, the functional group being part of an oximinopropenoxy system, and the deoxygenation temperature requirements is discussed. The significant decrease of th e deoxygenation temperature caused by the pressure of 12 kbar in the c ase of 2 is supposed to indicate the concerted character of the transf ormation.