The Gomberg–Bachmann reaction, named for the Russian-American chemist Moses Gomberg and the American chemist Werner Emmanuel Bachmann, is an aryl-aryl coupling reaction via a diazonium salt.
[1][2][3] The arene compound (here benzene) is reacted with a diazonium salt in the presence of a base to provide the biaryl through an intermediate aryl radical.
For example, p-bromobiphenyl may be prepared from 4-bromoaniline and benzene:[4] The reaction offers a wide scope for both diazonium component and arene component but yields are generally low following the original procedure (less than 40%), given the many side-reactions of diazonium salts.
One possibility is to employ diazonium tetrafluoroborates in arene solvent together with a phase-transfer catalyst,[5] another is to use 1-aryl-3,3-dialkyltriazenes.
[6] One intramolecular variation which gives better results is the Pschorr cyclization:[7][8][9] The group Z can be CH2, CH2CH2, NH and CO (to fluorenone[10]) to name just a few.