METHOD OF PRODUCING 4-FORMYL-6,7-DIHYDROXY-BENZO[B]THIOPHENE-3-CARBOXYLIC ACID ESTER Russian patent published in 2020 - IPC C07D333/68 

FIELD: chemistry.

SUBSTANCE: invention relates to organic synthesis, specifically to a method of producing ester of 4-formyl-6,7-dihydroxy-benzo[b]thiophene-3-carboxylic acid of structural formula

, where R is C1-C6 alkyl. Method includes reaction of 2,3-dialkoxythiophenol of formula , where R1 and R2 independently represent C1-C6 alkyl, with alkyl propiolate of formula in medium of acetonitrile in presence of radical reaction initiator to obtain 6,7-dialkoxy-benzo[b]thiophene-3-carboxylic acid ester of formula , followed by bromation and obtaining 4-bromo-6,7-dialkoxy-benzo[b]thiophene-3-carboxylic acid ester of formula , followed by cross-coupling with an alkyl ester of acrylic acid of formula , where R3 is C1-C6 alkyl, in the presence of a palladium-based catalyst to obtain (E)-4-(3-alkoxy-3-oxoprop-1-en-1-yl)-6,7-dialkoxybenzo[b]thiophene-3-carboxylic acid ester of formula , followed by oxidation with a mixture of alkali metal osmate and alkali metal periodate to obtain 4-formyl-6,7-dialkoxy-benzo[b]thiophene-3-carboxylic acid ester of formula , followed by dealkylation with boron trichloride or tribromide to obtain 4-formyl-6,7-dihydroxy-benzo[b]thiophene-3-carboxylic acid ester.

EFFECT: proposed method enables to synthesize ester from available starting substances with high output.

6 cl, 1 tbl, 5 ex