Dimethylformamide → 2-Formyl-3,5-dimethoxy-6-methylbenzoic acid methyl ester

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Reaction Steps

To a solution of 340 ml of N,N-dimethylformamide in 1 l of dichloromethane were added slowly 404 ml of phosphoryl chloride. The solution was stirred for 1.5 h at room temperature, and then, a solution of 618 g of 3,5-dimethoxy-2-methylbenzoic acid methyl ester in 200 ml of dichloromethane was added within 10 min. The mixture was heated for 72 h at reflux temperature. After cooling, the mixture was slowly poured into 3 l of ice-water and subsequently extracted with 3.6 l of dichloromethane. The organic layer was washed with 2 l of saturated sodium carbonate solution and twice with 2 l of water. The organic layer was dried over sodium sulfate and the solvent was evaporated in vacuo. The solid residue was triturated in 3 l of ethyl acetate at 60° C., and after cooling, 1.5 l of hexane were added. The solid was isolated by filtration to yield 646 g of 2-formyl-3,5-dimethoxy-6-methylbenzoic acid methyl ester, m.p. 164°-165° C.

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