Patent GB-615901-A (GB)
Title: Manufacture of 2-substituted furane-3:4-dicarboxylic acids and their corresponding tetrahydrofurane compounds
IPC: C07D307/68
Filed: 1945-09-19
Abstract: 2-Substituted furane and tetrahydrofurane-3 : 4-dicarboxylic acids are manufactured from starting materials of the general formula <FORM:0615901/IV(b)/1> (wherein R represents a carboxyl group or, as a substituent convertible (and, if desired, subsequently converted) into a carboxyl group a carboxylic acid ester or amide group, an aldehyde or acetal group, a nitrile group (convertible by hydrolysis, e.g. with an acid such as hydrochloric or sulphuric acid), a primary carbinol group (convertible by oxidation, e.g. with chromium trioxide in acetic acid or with potassium permanganate in alkaline solution) or a halogen atom (convertible by treatment with an alcoholic solution of potassium cyanide and hydrolysis of the resulting nitrile), and x represents a whole number, (e.g. 2, 3 or especially 4), by heating such a compound with an acetylene dicarboxylic acid ester, partially hydrogenating the resulting product in the presence of a hydrogenation catalyst (e.g. metals of the platinum group, as such, or on carriers, or catalytic forms of nickel), heating the hydrogenation product to eliminate one molecular proportion of ethylene therefrom and hydrolysing the resulting 2-substituted furane dicarboxylic acid ester to form the free dicarboxylic acid, which, if desired, is catalytically hydrogenated to give the corresponding tetrahydrofurane derivative.  In examples: (1) furyl-2-n-valeric acid ethyl ester is heated with acetylene dicarboxylic acid diethyl ester, the product is hydrogenated in ethyl acetate in the presence of palladium black, the hydrogenation product is distilled in vacuo and the resulting triethyl ester of furane-3 : 4-dicarboxy-2-n-valeric acid is saponified with alcoholic caustic potash and acidified to liberate the tricarboxylic acid, which is hydrogenated in aqueous caustic potash in the presence of Raney nickel and the product heated with methanol and sulphuric acid to produce 3 : 4-dicarbomethoxytetrahydrofurane - 2 - n - valeric acid methyl ester; (2) furyl-2-n-valeric acid is similarly converted to furane-3 : 4-dicarboxy-2-n-valeric acid (but using palladium supported on calcium carbonate as catalyst in the partial hydrogenation); (3) furyl-2-n-valeric acid piperidide is boiled with acetylene dicarboxylic acid dimethyl ester in benzene, the product is hydrogenated in methanol in the presence of Raney nickel, the hydrogenation product is distilled in vacuo and the resulting ester is saponified to furane-3 : 4-dicarboxy-2-n-valeric acid piperidide, which is hydrolysed with a mixture of glacial acetic and concentrated hydrochloric acid to yield the product of (2); (4) furyl-2-n-valeraldehyde dimethyl acetal is heated in a sealed tube with acetylene dicarboxylic acid dimethyl ester, the product is hydrogenated in ethyl alcohol in the presence of platinum black, the hydrogenation product is distilled in vacuo and the product is saponified to 3 : 4-dicarboxyfuryl-2-n-valeraldehyde, which is oxidized to the acid by means of silver oxide in caustic soda; (5) furyl-2-n-butyric acid is refluxed with acetylene dicarboxylic acid diethyl ester in toluene, the product is hydrogenated in ethyl alcohol in the presence of palladium supported on barium sulphate, the hydrogenation product is distilled in vacuo and the resulting ester is hydrolysed to 3 : 4-dicarboxyfurane-2-n-butyric acid. Additional starting materials specified are, on the one hand, furane derivatives in which R in the general formula above represents a carboxylic acid methyl, propyl, phenyl or benzyl ester or amide, mono- or di-methylamide, diethylamide, anilide or N-methylanilide group, and, on the other hand, the propyl, isopropyl, phenyl and benzyl esters of acetylene dicarboxylic acid.  The Specification as open to inspection under Sect. 91 comprises also the hydrogenation of 3 : 4 - dicarbethoxyfurane - 2 - n - valeric acid piperidide in ethyl alcohol in the presence of nickel on kieselguhr, producing the corresponding tetrahydrofurane derivative.  This subject-matter does not appear in the Specification as accepted.