Proton magnetic resonance of some 9,10-dihydroanthracenes

Abstract

Reaction of dilithio- or disodio-anthracene with t-butyl chloride affords a mixture of 9-t-butyl- and 9,10-di-t-butyl-9,10-dihydroanthracene with some 1,4-di-t-butyl-1,4-dihydroanthracene. The nuclear magnetic resonance (n.m.r.) spectrum of the 9,10-di-t-butyl compound shows that it has either a planar conformation of the central ring or the trans configuration with rapid interconversion of the two conformers. Homo-allylic coupling is observed in the n.m.r. spectra of 9-t-butyl-9,10-dihydroanthracene and 1-phenyl-1,4-dihydronaphthalene, in the latter case with a coupling constant of 6 c./sec.