[mana]

hi all
does coupling reaction of diazonium with other substituted aromatic compounds has any limitation?
I mean is it important that what substituent is on the aromatic compound which is coupling with diazonium salt? or vice versa?

[rolnor]

Yes, the molecule coupling with diazoniumsalts must be activated by electrondonating groups.

[mana]

Yes, the molecule coupling with diazoniumsalts must be activated by electrondonating groups.

I have seen somewhere (in google images) that only the NR₂ and OH can be on the molecule which coupled with diazonium salt!!! is it true? for example toluene can not couple with diazonium salt?

[wildfyr]

Hm... so wikipedia shows that the resonance form of phenol (a quinone) is part of the mechanism. The amine version of this resonance form (name escaping me) would impart similar stability at the para location, and explain why the reaction tends to be pretty specific for that location.

I'm racking my brain but cannot come up with an example of an azo coupling that doesn't contain a phenol or aniline. It is possible that you just need a group that will stabilize the resonance form enough to make it a viable spot. In that case alkoxy substitution, thiols and even halides may be reactive under the right conditions.