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The Friedel-Crafts Reaction of 2,3-Dimethylbenzofuranyl Ketones and the Corresponding Carboxylic Esters

1970; Oxford University Press; Volume: 43; Issue: 9 Linguagem: Inglês

10.1246/bcsj.43.2884

1348-0634

Yoshiyuki Kawase, Tomoko Okada, Toshio Miwa,

Multicomponent Synthesis of Heterocycles

Abstract The acetylation of methyl 2,3-dimethyl-4- and -7-benzofurancarboxylates was carried out by the action of acetyl chloride and aluminum chloride in carbon disulfide at room temperature to afford the 6-acetyl compounds; these compounds were converted to keto-acids by hydrolysis, and then to the known dicarboxylic acid or to the known 6-acetylbenzofuran. The alkylation of acetyl and methoxycarbonyl derivatives of 2,3-dimethylbenzofuran was carried out by the action of n- or iso-propyl bromide and aluminum chloride in carbon disulfide at reflux temperature, both the bromides furnishing the same isopropylated product. The crude products from the 4-acetyl- and 4-methoxycarbonyl-benzofurans could not be purified, but 2,3-dimethyl-6-isopropyl-4-benzofurancarboxylic acid was obtained by the hydrolysis of the product from the latter. In the cases of 5-acetyl- and 5-methoxycarbonyl-benzofurans, the isopropylation occurred at the 7-position and the products were converted to the same carboxylic acids, while the isopropylation occurred at the 4-position in the cases of 6-acetyl- and 6-methoxycarbonylbenzofurans, and diisopropylation occurred in the case of 7-methoxycarbonylbenzofuran.