Aromatic compounds chemoselective acylation

Bottom reaction (as a reminder) chemoselective acylation of an aromatic compound with an activated carboxylic chloride (Friedel-Crafts acylation, cf. Section 5.2.7). 

Aggen DH, Arnold JN, Hayes PD, Smoter NJ, Mohan RS (2004) Bismuth compounds in organic synthesis. Bismuth nitrate catalyzed chemoselective synthesis of acylals from aromatic aldehydes. Tetrahedron 60 3675-3679... 

In a bifunctional compound, if a reagent reacts with one functional group preferentially, even though the other is apparently susceptible to the reaction conditions, the reaction is said to be chemoselective. Two illustrative examples are the reduction of a carbonyl group in the presence of a cyano, nitro or alkoxycarbonyl group (Section 5.4.1, p. 519 see also Metal hydrides, Section 4.2.49, p. 445) and the acylation of an aromatic amino group in the presence of a phenolic group (Section 6.9.3, p. 984). 

One of the effective reagents for highly chemoselective dithioacetalization of carbonyl compounds is ceric ammonium nitrate (CAN) in chloroform. When a mixture of benzaldehyde and acetophenone was allowed to react with 1,2-ethanedithiol and a catalytic amount of CAN, the 1,3-dithiolane derived from the aldehyde was obtained in 84% yield while the ketone was recovered unchanged. It is noteworthy that aromatic ketones, 7-lactones, and acylic ketones did not react at all under these conditions and even at elevated temperatures for longer reaction times <1995T7823>. 

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