Direct arylations silver nitrate

We have seen (Sec. 14.24) that an alkyl halide is conveniently detected by the precipitation of insoluble silver halide when it is warmed with alcoholic silver nitrate. The reaction occurs nearly instantaneously with tertiary, allyl, and benzyl bromides, and within five minutes or so with primary and secondary bromides. Compounds containing halogen joined directly to an aromatic ring or to a doubly-bonded carbon, however, do not yield silver halide under these conditions. Bromo-benzene or vinyl bromide can be heated with alcoholic AgN03 for days without the slightest trace of AgBr being detected. In a similar way, attempts to convert aryl... 

Nitric acid (70 %) or the mixture of nitric acid and sulfuric acid or other mixed acids with catalytic function can nitrate secondary nitroalkanes directly into gem-inal dinitroalkane [8]. With the sodium alkoxide and tetranitromethane, primary nitroalkanes can be nitrated into dinitroalkanes and trinitroalkanes [9]. In a neutral or basic solvent, primary, secondary nitroalkane salts can be nitrated, step by step, into gem-dinitroalkanes by silver nitrate and sodium nitrite [10]. Alkali metal salts of aryl nitroalkanes can be nitrated, step by step, into dinitroalkanes and trinitroalkanes by dinitrogen tetroxide [11]. 

A new approach for direct arylation of pyridine W-oxides with arylboronic acids through C-H functionalization has been developed (Scheme 45) [99]. This reaction can be performed at room temperature using catalytic silver (I) nitrate in the presence of potassium persulfate, thus giving 2-aryl derivatives of pyridine W-oxides. 

Benzoyliminopyridinium ylide couples with phenylboronic acids at C-2 and C-4 (Scheme 37).This direct C-H arylation occurs at room temperature with an inexpensive catalyst silver nitrate with potassium persulfate. An excess of the phenylboronic acid was necessary for a high conversion additionally, using phenylboronic acid pinacol ester decreased the yield. Coupling a quinoline ylide also resulted in a mixture of C-2 and C-4 arylation, with a slight preference for the C-2. Alkylated pyridine ylides also coupled with a mixture of C-2 and C-4 arylations when possible (14SL1413). 

Positive tests for aryl halides are difficult to obtain directly, and some of the best evidence for their presence involves indirect methods. Elemental analysis indicates the presence of halogen. If both the silver nitrate and sodium iodide-acetone tests are negative, the compound is most likely a vinyl or an aromatic halide, both of which are very unreactive toward silver nitrate and sodium iodide. Distinction between a vinyl and an aromatic halide can be made by means of the aluminum chloride-chloroform test. 

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