Structural studies on phenanthro[9,10-e]pyrene and its 9,10-dihydro-derivative: dependence of chemical shift on degree of planarity of and buttressing effect in the polycyclic aromatic compounds

Abstract

The first example of a transannular reaction of a syn-[2,2]metacyclophane derivative via photochemical iodination has been employed in the preparation of 9,10-dihydrophenanthro[9,10-e]-pyrene (2). The structural studies of 2 and the phenanthropyrene 1 were carried out by 1D and 2D NMR spectroscopic analyses. Qualitative correlation between tilting of the fused moieties and the change in deshielding effect was observed by probing the chemical shifts of H3 and H1′(H6 and H8′). Buttressing effects resulting from the steric interaction of H3 and H1′(H6 and H8′), although differing in magnitudes for the two groups of protons (H3→H2→H1→H10 and H1′→H2′→H3′→H4′), seem to transmit evenly among those on the same moiety according to a simple additivity rule.