Yield:-

Reaction Conditions:

with potassium carbonate in N,N-dimethyl-formamide at 20; for 18 h;

Steps:

1.1.A

A) Methyl 4,5-dibromo-3-methoxythiophene-2-carboxylate 9.97 ml of a solution of iodomethane and then 29.44 g of K₂CO₃ are added, dropwise, to a solution of 34.35 g of methyl 4,5-dibromo-3-hydroxythiophene-2-carboxylate in 150 ml of DMF and the mixture is left to stir for 18 hours at AT. After cooling, the reaction mixture is diluted in 100 ml of ethyl ether and filtered, and the filtrate is concentrated under vacuum. The reaction crude is purified by silica gel chromatography, elution being carried out with heptane and then with a heptane/EtOAc mixture (85/15; v/v). 28.70 g of the expected compound are obtained.

References:

US2012/115906,2012,A1 Location in patent:Page/Page column 17