Aluminum(III) Chloride → HCID 136053481, compound

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Reaction Steps

In accordance with the Flowchart I, 2,5-dimethyl furan (formula 12) is reacted in step A with CH3CO2 (--C≡C--)CO2CH3 (formula 13) to produce 1,4-dimethyl-7-oxabicyclo[2,2,1]octa-2,5-diene-2,3-dicarboxylic acid, dimethyl ester (formula 14). The latter is catalytically hydrogenated in ethyl acetate (step B) to produce 2,5-dimethyl-3,4-furandicarboxylic acid, dimethyl ester (formula 15), which is treated with aqueous base at reflux for several hours and then acidified to produce 2,5-dimethyl-3,4-furandicarboxylic acid (formula 16). The latter is then treated (Step D) with thionyl chloride at reflux to produce 2,5-dimethyl-3,4-furandicarbonyl chloride (formula 17), which is then reacted in Step E with 1,4-dimethoxybenzene and anhydrous stannic chloride in dichloromethane at 0°-5° C. for several hours, and then acidified under an inert atmosphere. The product is extracted at 40°-45° C. in chloroform and chromatographed, to produce 1,3-dimethyl-5,8-dimethoxynaphtho[2,3-c]furan-4,9-dione (formula 18). Such dione (18) is then treated in step F with anhydrous aluminum chloride in dichloromethane at 40°-45° C. for several hours, acidified and extracted at 50°-55° C. into chloroform and crystallized from glacial acetic acid, to produce 1,3-dimethyl-5,8-dihydroxynaphtho[2,3-c]furan-4,9-dione (formula 19). The latter is then treated in step G with lead tetraacetate in acetic acid and extracted with dichloromethane, to produce 1,3-dimethylnaphtho-[2,3-c]furan-4,5,8,9-tetrone (formula 20).

Provenance & Evidence