| Summary: | The synthesis of new phenanthr[9,10-<i>e</i>][1,3]oxazines was achieved by the direct coupling of 9-phenanthrol with cyclic imines in the modified <i>aza</i>-Friedel–Crafts reaction followed by the ring closure of the resulting bifunctional aminophenanthrols with formaldehyde. Aminophenanthrol-type Mannich bases were synthesised and transformed to phenanthr[9,10-<i>e</i>][1,3]oxazines via [4 + 2] cycloaddition. Detailed NMR structural analyses of the new polyheterocycles as well as conformational studies including Density Functional Theory (DFT) modelling were performed. The relative stability of <i>ortho</i>-quinone methides (<i>o</i>-QMs) was calculated, the geometries obtained were compared with the experimentally determined NMR structures, and thereby, the regioselectivity of the reactions has been assigned.
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