Protonation, quaternisation, and stereochemistry of 2,2′-biphenylylene-bisdimethylamine. The thermal decomposition of related salts and the mechanism of cyclisation of 2,2′-diaminobiphenyl to carbazole

Abstract

The reaction of the ditertiary amine, 2,2′-biphenylylenebisdimethylamine, with methyl iodide has been re-examined and shown to give both the monohydriodide and monomethiodide. The H n.m.r. spectra of the above salts have been studied and provide examples of magnetic nonequivalence of methyl groups attached to nitrogen in a dissymmetric system.The thermal decomposition of the above salts, and of 2,2′-diaminobiphenyl dihydrobromide, has been examined; the results suggest that the formation of carbazole from 2,2′-diaminobiphenyl on heating with acid proceeds via an SNi mechanism, as has been suggested for the conversion of related bisphosphonium salts to phosphafluorenes.