Abstract: Methyl-[2-(2,4,6-tribromophenylcarbamoyl-)ethyl-]phosphinic acid is made continuously. To this end, molten 2-methyl-2,5-dioxo-1-oxa-2-phospholane is reacted with molten 2,4,6-tribromoaniline at 210.degree. to 250.degree. C. in the absence of a solvent.

Abstract: Production of N-substituted 2-carbamoyl phosphinic acids of the general formula: ##STR1## in which R.sup.1 stands for an alkyl group having 1 to 4 carbon atoms or an aryl group; R.sup.2 and R.sup.3 stand independently of each other for an alkyl group having 1 to 4 carbon atoms, an aryl group or a hydrogen atom; R.sup.4 stands for an alkyl group having 1 to 18 carbon atoms, an aryl group or a hydrogen atom; and R.sup.5 stands for an alkyl group having 1 to 18 carbon atoms or an aryl group. More specifically, a 2-chloroformyl phosphinic acid chloride of the general formula ##STR2## is reacted at 120.degree. to 170.degree. C with an amine of the general formula ##STR3## and resulting N-substituted 2-carbamoyl phosphinic acid chloride of the general formula ##STR4## the latter compound being obtained while hydrogen chloride is split off, is hydrolyzed with water.

Abstract: Continuous production of 2,5-dioxo-1-oxa-2-phospholanes of the general formula ##STR1## from a beta-halogenoformyl-ethyl phosphinic acid halide of the general formulaR.sup.1 XP(O)--CHR.sup.2 --CHR.sup.3 --CO--Xin which formula R.sup.1 stands for an alkyl radical having 1, 2, 3 or 4 carbon atoms, or a phenyl radical, R.sup.2 and R.sup.3 each stands for hydrogen or CH.sub.3, and X stands for chlorine or bromine, by reacting the said acid halide with acetic anhydride. The phospho lanes are produced by introducing, into a heatable circulation reactor, an initial quantity of the desired 2,5-dioxo-1-oxa-2-phospholane and circulating it therein at a temperature of 110.degree. to 190.degree. C; separately preheating the respective beta-halogenoformyl-ethyl phosphonic acid halide and acetic anhydride starting materials to a temperature of 60.degree. to 160.degree.

Abstract: Beta-halogenoformyl-ethyl phosphinic acid halides of the general formula:R.sup.1 XP(O)--CHR.sup.2 --CHR.sup.3 --CO--X,in which R.sup.1 stands for an alkyl radical having 1, 2, 3 or 4 carbon atoms or a phenyl radical, R.sup.2 and R.sup.3 each stand for hydrogen or CH.sub.3, and X stands for chlorine or bromine, are produced by reacting an alkyldihalogenophosphine having 1, 2, 3 or 4 carbon atoms in its alkyl radical, or a phenyldihalogenophosphine, with acrylic acid, methacrylic acid or crotonic acid. To this end, a quantity of the desired beta-halogenoformyl-ethyl phosphinic acid halide is introduced into a reaction zone and circulated in the form of a melt at 50.degree. to 120.degree. C and at a flow rate of 0.1 to 3 m/s.