Synthesis and Analgesic Activity of Some Substituted 1-Benzofurans and 1-Benzothiophenes

Abstract

2-Benzoyl- and 2-(pyridylcarbonyl)-1-benzofuran-3-amines were prepared from 2-hydroxybenzonitrile and corresponding bromoethanone derivatives. 2-Benzoyl- and 2-(pyridylcarbonyl)-1-benzothiophene-3-amines were prepared analogously from 2-sulfanylbenzonitrile. 2-Benzoyl-1-benzofuran-3-amine treated with acetic anhydride or ethyl chloroformate provided the corresponding N-acetyl or N-ethoxycarbonyl derivatives. These N-activated compounds were alkylated with ethyl bromoacetate to provide ethyl N-acetyl-N-(2-benzoyl-1-benzofuran-3-yl)glycinate and ethyl N-(2-benzoyl-1-benzofuran-3-yl)-N-ethoxycarbonylglycinate, respectively. Their mild hydrolysis gave the corresponding glycine derivatives. Methylation of ethyl N-(2-benzoyl-1-benzofuran-3-yl)carbamate gave the corresponding N-methyl carbamate, which was hydrolyzed to N-methyl-(2-benzoyl-1-benzofuran-3-yl)amine. 2-Benzoyl-7-methoxy-1-benzofuran-3-amine and 2-(4-methoxybenzoyl)-1-benzofuran-3-amine were demethylated with boron tribromide to the corresponding hydroxy derivatives; their O-alkylation with ethyl bromoacetate than gave ethyl [(3-amino-2-benzoyl-1-benzofuran-7-yl)oxy]acetate and ethyl {4-[(3-amino-1-benzofuran-2-yl)carbonyl]phenoxy}acetate, respectively. The mild hydrolysis of these esters provided corresponding acids. Similarly, alkylation of the hydroxy derivatives with (dimethylamino)propyl chloride gave corresponding (dimethylamino)propoxy derivatives. 2-Hydroxybenzonitrile treated with 2-bromo-1-(2-, 3-, or 4-pyridyl)ethan-1-one provided the respective 2-(pyridylcarbonyl)-1-benzofuran-3-amine. Similar 2-(pyridylcarbonyl)-1-benzothiophene-3-amines were prepared analogously from 2-sulfanylbenzonitrile. 2-Benzoyl-3-(bromomethyl)-1-benzofuran treated with dimethylamine, 1-methylpiperazine, and sodium 1-methylpiperidine-4-thiolate gave the corresponding alkylation products. Several compounds were found to exhibit considerable analgesic activity.