Arene from arenediazonium salts

Arylamines are converted by diazotization with nitrous acid into arenediazonium salts, ArN2+ X-. The diazonio group can then be replaced by many other substituents in the Sandmeyer reaction to give a wide variety of substituted aromatic compounds. Aryl chlorides, bromides, iodides, and nitriles can be prepared from arenediazonium salts, as can arenes and phenols. In addition to their reactivity toward substitution reactions, diazonium salts undergo coupling with phenols and arylamines to give brightly colored azo dyes. 

We have seen that primary arylamines react with nitrous acid to form stable arene-diazonium salts (Section 16.12). Arenediazonium salts are useful to synthetic chemists because the diazonium group can be replaced by a wide variety of nucleophiles. This reaction allows a wider variety of substituted benzenes to be prepared than can be prepared solely from electrophilic aromatic substitution reactions. 

Arenediazonium salts ArN2Bp4 are an excellent substrate available from aromatic amines for carrying out oxidative addition under mild conditions. The desired cross-coupling with aryl(trifluoro)borates (ArBp3)K is achieved at room temperature with 5 mol% of Pd(OAc)2 or with the paradacycle shown in Eq. 26 (Eq. 46). Biaryl coupling of arene... 

---