Toluene reaction with benzenediazonium

In refluxing toluene, thiopivalophenones yield both 2H-l-benzothietes and lH-2-benzothiopyrans. Using benzenediazonium-2-carboxylate, as a benzyne precursor, the reaction with 4111 yields a 4H-3,l-benzoxathian-4-one, and selenobenzophenone derivatives18,111 give 4H-3,l-benzooxaselenin-4-ones (see later Scheme 34). 

Most of the side reactions have already been discussed in Section 26.1.3.3. (dediazoniation in organic solvents). Chlorinated aliphatic solvents, such as 1,2-dichloroethane and dichloro-methane, lead to an extensive formation of chloroaromatics, and aromatic solvents, even halogenated examples, can be arylated to some extent by arenediazonium tetrafluoroborates (vide supra). For example, during dediazoniation of benzenediazonium tetrafluoroborate in toluene, chlorobenzene, bromobenzene or anisole, 3-5 % of substituted biphenyls Ph-C6H4-X (X = Me, Cl, Br, OMe) are formed together with 0.5-0.8% of fluorobiphenyls.5 Fluorobiphenyls are formed through an ionic pathway (only 2- and 4-isomers are formed) whereas chlorobiphenyls result from a radical process (X = Cl, 2-/3-/4-isomer 26 47 27).243... 

Write down the formulae of the products of the reaction of p-cresol (4) with each of the following reagents (a) toluene-4-suI-fonyl chloride and dil. sodium hydroxide (b) bromine water (c) benzenediazonium chloride (d) chloroform and aq. sodium hydroxide at 70 °C (e) carbon dioxide and aq. sodium hydroxide at 125 °C under pressure (f) alkaline potassium ferricyanide. 

In basic solutions, of an activated aromatic substrate, diazonium salts decompose and eouple to give biaryls (Ar-Ar).2 9 Reaction of benzenediazonium ion (398) and toluene gave a 67% yield of 411, along with 19% of 412 and 14% of 413. This result suggests the coupling is rather unselective. Selectivity is observed only when the substituent is part of the aryl diazonium ion, as in the eonversion of 414 to 415. ... 

---