Condensed diazepines. synthesis of 1-aryl-3,5-dihydro-4H-1-benzofuro-[2,3-d][1,2]diazepin-4-ones

Abstract

Keywords:(2-aroyl-1-benzofuran-3-yl)-acetic acids, 1-aryl-3,5-dihydro-4H-1-benzofuro [2,3-d][1,2]diazepin-4-ones, hydrazine hydrate, condensed diazepines, polyphosphoric acid, benzoylation, cyclization.1-Aryl-3,5-dihydro-4H-2,3-benzodiazepin-4-ones are actively studied in connection with the anticonvulsive activity detected in them [1][2][3][4]. Known routes to obtain them are based on the interaction of 2-aroyl-4,5-dimethoxyphenylacetic acids or their esters with hydrazine [1-6]. Of the heterocyclic analogs of 2,3-benzodiazepin-4-ones only 3H-[1,2]diazepino[5,6-b]indoles, obtained by the cyclocondensation of the ethyl ester of [2-formyl(acetyl)indol-2-yl]acetic acid with hydrazine hydrate are known [7-9]. Similar conversions have not been described in the 1-benzofuran series. As was shown in our preliminary publication [10], heterocyclization of hydrazones of (2-acyl-1-benzofuran-3-yl)acetic acid leads to the corresponding azine, but heterocyclization of hydrazones of arylamides of (2-acetyl-1-benzofuran-3-yl)acetic acid, depending on the conditions, takes place with the formation of 2-amino-1-methyl-1-benzofuro[2,3-c]pyridin-3-one or azines of arylamides of (2-acetyl-1-benzofuran-3-yl)acetic acid.In the present work the reaction of methyl esters of (2-aroyl-1-benzofuran-3-yl)acetic acids 2a-g and (2-aroyl-1-benzofuran-3-yl)acetic acids 4a-c with hydrazine hydrate has been investigated. The initial esters 2a-g were obtained by acylation of the methyl ester of (6-methyl-1-benzofuran-3-yl)acetic acid (1) with aroyl(heteroyl) chlorides in the presence of aluminum chloride.Acylation of methyl ester 1 with benzoic, veratric, and thiophene-2-carboxylic acids in polyphosphoric acid (PPA) leads to 7-methyl-1-phenyl-3H-pyrano [3,4-b][1]benzofuran-3-one (3a), 7-methyl-1-(thien-2-yl)-3H-pyrano [3,4-b][1]benzofuran-3-one (3b), and 1-(3,4-dimethoxyphenyl)-7-methyl-3H-pyrano [3,4-b][1]benzofuran-3-one (3c), from which (2-aroyl-1-benzofuran-3-yl)acetic acids 4a-c were obtained by alkaline hydrolysis.