SYNTHESIS OF 2-ARYL-10B,10C-DIMETHYL-10B,10C-DIHYDROPYRENES AND A STUDY OF THEIR CONJUGATION BEHAVIOR - LINEAR RELATIONSHIP BETWEEN THE DEGREE OF CONJUGATION AND THE ELECTRONIC NATURE OF SUBSTITUENTS

A new Gomberg-Bachmann reaction between 10b,10c-dimethyl-10b,10c-dihyd ropyrene (3) and an arenediazonium salt under acidic conditions afford ed a mixture of mono- and diarylated derivatives of 3. The major produ ct was 2-aryl-10b,10c-dimethyl-10b,10c-dihydropyrene 6. The desired pr oducts were obtained only from diazonium salts prepared from anilines with at least one strongly electron-withdrawing substituent. The combi ned conjugation and electronic effects of the arene substituent on the diatropicity of the dihydropyrene moiety in the monoarylated product is insignificant. The conjugation effect in 6 is, however, readily obs erved by the color appearance of 6 in the solid state and tile signifi cant red shift in the absorption bands between 300 and 520 nm in its e lectronic spectrum. A linear relationship was in fact obtained when th e degree of conjugation (rho band lambda(max) values) is correlated wi th the electronic nature (sigma(+) values) of the corresponding substi tuents.