Thieno pyridine-5-carboxylates 4-chloro

In 1972 Wright prepared 3-chlorothieno[3,2-6]thiophene-2-carbonyl chloride (94) in 11-13% yield by heating 3-(2-thienyl)acrylic acid, thionyl chloride, and pyridine, a method of synthesis of benzo[6]-thiophene-2-carbonyl chloride derivatives. " Methyl 3,5-dichloro-thieno[3,2-6]thiophene-2-carboxylate (95) and methyl 2-chloro-3-(5-chloro-2-thienyl)acrylate were also isolated. When fte reaction was carried out in refluxing toluene or chlorobenzene, the acid chloride (94)... 

Later Gronowitz and Maltesson reported the extension of this method to the preparation of thieno[2,3-6]thiophene (1) derivatives. A mixture of 3-(3-thienyl)acrylic acid, thionyl chloride, and pyridine was heated for 24 hours. 2-Chloro-3-(3-thienyl)-acrylic acid (4.5%), 3,5-dichlorothieno[2,3-6]thiophene-2-carbonyl chloride (99) (9.5%), 3-chlorothieno[2,3-Z)]thiophene-2-carbonyl chloride (100) (79.1%), and other compounds were detected by GLC among the reaction products [Eq. (31)]. Hydrolysis of the reaction mixture gave 3-chlorothieno[2,3-Z>]thiophene-2-carboxylic acid in 63% yield dechlorination of the latter by copper in propionic acid converted it into thieno[2,3-6]thiophene-2-carboxylic acid. 

Chloro-4-hydroxy-2-methyl-1,1 -dioxo-1,2-dihydro-1 l6-thieno[2,3 e][1,2]thiazine-3-carboxylic acid pyridin-2-ylamide, 6-chloro-4-hydroxy-2-methyl-/V-(2-pyridyl)-2H-thieno[2,3-e]-1,2-thiazine-3-carbox-amide-1,1-dioxide, CnH,oC N30AS2, Mr 371.81, mp 225-230 °C (decomp.)... 

Thieno[2,3-6]pyridine-5-carboxylic acid, 4-chloro-2-methyl-... 

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