Patent GB-594697-A (GB)
Title: Alkamine esters of 1-alkylpyrrole-3,4-dicarboxylic acids
IPC: C07D207/34
Filed: 1944-06-24
Abstract: Dialkamine esters of pyrroledicarboxylic acids, of the general formula <FORM:0594697/IV/1> (wherein R represents an alkyl group, R1 and R2 represent lower alkyl groups of not more than 6 carbon atoms, and X represents a dialkylaminoalkyl radical in which the two alkyl groups attached to nitrogen contain not more than 6 carbon atoms each), are manufactured by (a) reacting a dialkyl ester of the same acid, in the presence of a catalytic amount of alkali metal alcoholate, with such a proportion (preferably 10-12 molecular proportions) of the desired dialkylaminoalcohol as will yield substantially the dialkamine ester, or by (b) transforming the dicarboxylic acid (obtainable by hydrolysis the dialkyl esters) into the acid chloride and esterifying this with a dialkylaminoalcohol. Some of the products are useful as activators for rubber accelerators, and others as local an sthetics, preferably in the form of their salts, e.g. the hydrochlorides obtained by passing dry hydrogen chloride into a solution of the ester in dry ether.  In examples: (1) diethyl 1 : 2 : 5-trimethylpyrrole-3 : 4-dicarboxylate is refluxed with excess of b -diethylaminoethanol in which a small amount of sodium has been dissolved, and the product is isolated in the form of its hydrochloride; (2) the potassium salt of 1 : 2 : 5-trimethylpyrrole-3 : 4-dicarboxylic acid is treated with thionyl chloride, the product is warmed with g -diethylaminopropanol in benzene and the resulting ester is isolated in the form of its hydrochloride, from which the free base may be regenerated with sodium hydroxide solution; the g -diethylaminopropanol may be replaced by b -diethylaminoethanol; (3) the b -diethylaminoethanol in (1) is replaced by g -diethylaminopropanol; (4) diethyl 1-ethyl-2 : 5-dimethylpyrrole-3 : 4-dicarboxylate is treated as in (1); (5) the corresponding 1-n-butyl compound is similarly treated; (6) 1-n-butyl-2 : 5-dimethylpyrrole-3 : 4-dicarboxylic acid is treated with thionyl chloride and the product is warmed with b -diethylaminoethanol in benzene; (7) the b -diethylaminoethanol in (5) is replaced by g -diethylaminopropanol; (8) 1-isoamyl-2 : 5-dimethyl-3 : 4-dicarbethoxypyrrole is treated as in (1); (9) as in (8) but using a smaller excess of b -diethylaminoethanol; (10) diethyl 1-n-hexyl-2 : 5-dimethylpyrrole-3 : 4-dicarboxylate is treated as in (1) (but omitting the conversion to hydrochloride); (11) the corresponding 1-n-decyl compound is similarly treated. Instead of dissolving the sodium initially in the dialkylaminoalcohol, it may be added to the reaction mixture, or it may be dissolved in a separate amount of dialkylaminoalcohol or in ethyl alcohol and the preformed alcoholate added to the reaction mixture, or potassium may be used instead of sodium. Specification 594,698 is referred to.  The dialkyl esters employed as starting materials are obtainable by condensation of primary alkylamines with diacylsuccinates, e.g. with diacetosuccinates (in which case R1=R22CH3) or with dipropionosuccinates or higher members of the series, up to the diheptoylsuccinates. Thus diethyl 1-ethyl-, 1-n-butyl-, 1-isoamyl- and 1-n-decyl-2 : 5-dinethylpyrrole-3 : 4-dicarboxylates are obtainable by condensing diethyl diacetosuccinate with ethylamine, n-butylamine, isoamylamine and n-decylamine, respectively, e.g. in glacial acetic acid.