GB649551A - Improvements in halogen containing derivatives of dicarboxylic acids - Google Patents

Abstract

1 : 1 : 1-Tri-chloro-3-bromo-2 : 3-dicarbalkoxy propanes and 1 : 1 : 1 - trichloro - 5 - bromo-2 : 3 : 4 : 5-tetracarbalkoxy pentanes are prepared from a dialkyl ester of maleic or fumaric acid and trichlorobromomethane by subjecting them to either actinic light or a peroxide polymerization catalyst used at a temperature at which it will decompose. The products may be dehydrobrominated with sodium methoxide. Suitable peroxide catalysts include the diacyl peroxides, e.g. dibenzoyl peroxide, hydrogen peroxide, and peroxysulphates. The dialkyl maleates or fumarates may be the di-isopropyl, di-n-butyl, diamyl, dihexyl, or mixed esters, e.g. the methyl hexyl ester. In the examples, dimethyl maleate or fumarate is treated with trichlorobromomethane in presence of actinic light or a peroxide to give 1 : 1 : 1-trichloro-3-bromo-2 : 3-dicarbomethoxypropane or 1 : 1 : 1-trichloro - 5 - bromo - 2 : 3 : 4 : 5 - tetracarbomethoxypentane; the latter compound is treated with sodium methoxide to give 1 : 2 : 3 : 4-tetracarbomethoxy - 5 : 5 : 5 - trichloropentene - 1, further treatment of which with sodium methoxide gives 1 : 2 : 3 : 4 : 4-pentacarbomethoxybutene-1, which after hydrogenation is hydrolysed and decarboxylated to give butane 1 : 2 : 3 : 4-tetracarboxylic acid. Specification 14281/47 (as open to inspection under Sect. 91) is referred to.