Equatorenes: Synthesis and Properties of Chiral Naphthalene, Phenanthrene, Chrysene, and Pyrene Possessing Bis(1-adamantyl) Groups at the Peri-position

Chiral polycyclic aromatic hydrocarbons
containing bis­(1-adamantyl)
groups at the peri-positions, named equatorenes, were synthesized
in optically pure form starting from optically pure 4,5-bis­(1-adamantyl)-8-methoxy-1-naphthol.
A sequential Diels–Alder reaction of furan and arynes generated
from 1,2-bromotriflates provided tricyclic and tetracyclic epoxides,
and acid-catalyzed aromatization gave phenanthrol and chrysenol. Deoxygenation
reactions involving the hydrogenolysis of triflates gave 1,8-bis­(1-adamantyl)­naphthalene,
1,10-bis­(1-adamantyl)­phenanthrene, and 1,12-bis­(1-adamantyl)­chrysene.
3,4-Bis­(1-adamantyl)­pyrene was synthesized from phenanthrol by Sonogashira
coupling and Pt-catalyzed cyclization. Essentially no racemization
occurred during the synthesis. X-ray analysis indicated the distorted
naphthalene moiety possessing the peri-diadamantyl groups and the
flat structure of the other benzene rings. UV–vis analysis
of the equatorenes showed considerable redshifts compared with that
of the corresponding achiral arenes. Electrochemical analysis of the
naphthalene and pyrene indicated that the distortion decreased the
highest occupied molecular orbital stability with no marked effect
on the lowest unoccupied molecular orbital energy level, and the origin
was discussed on the basis of calculation results.