Synthesis of potentially basic hydrocarbons by sulphur extrusion and/or bis-Wittig reactions. Two syntheses of benz[5,6]indeno[2,1-a]phenalene and a new synthesis of dibenzo[de,mn]naphthacene (zethrene)

Abstract

Macrocyclic bis-sulphides have been prepared from 1,2-, 2,3-, and 1,8-bis(bromomethyl)naphthalenes. Methylation of the bis-sulphides, followed by the Stevens rearrangement, gave the corresponding carbocycles with extra-annular sulphide groups; removal of these sulphide groups by Hofmann elimination led to spontaneous trans-annular condensation. Using this general method, two hydrocarbons were synthesized: benz[5,6]indeno[2,1-a]-phenalene and dibenzo[de,mn]naphthacene (or zethrene). An alternative synthetic route led to the synthesis of benz[5,6]indeno[2,1-a]phenalene, using the Wittig reaction between naphthalene-2,3-carbaldehyde and 1,8-bis(triphenylphosphoniomethyl)naphthalene dibromide.