The catalytic hydrogenation of salicyloyl chloride at a mild temperature gave a high yield of salicylaldehyde. A similar partial reduction of substituted salicyloyl chlorides provided the corresponding salicylaldehydes in appreciable yields. Attempts to prepare other isomeric hydroxybenzoyl chlorides were, however, unsuccessful. The relationship between the structure of salicyloyl chlorides and the ease of their conversion to salicylaldehydes is discussed. Moreover, the formylation of phenol with dichloromethyl methyl ether and the selective ortho-formylation are described.
The aluminum chloride-catalyzed reaction of aromatic compounds, such as benzene and phenols, with β-chlorocarboxylic acids was investigated. Although the reactions of benzene, toluene, and chlorobenzene with β-chloropropionic acid were found to give the corresponding dihydrocinnamic acids in high yields, attempts to prepare dihydrocoumarin by a similar reaction of phenol were unsuccessful. Similarly, β-arylbutyric acids were obtained in good yields by means of the aluminum chloride-induced reaction of aromatic hydrocarbons with β-chlorobutyric acid (Ib). In contrast, phenols, such as phenol, o- and m-cresols, reacted with Ib under similar conditions to provide the corresponding β-(p-hydroxyphenyl)butyric acids in 22–60% yields, while a 51% yield of β-(5-hydroxy-2-methylphenyl) butyric acid was obtained upon a similar treatment of p-cresol with the acid Ib.
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