Method for producing phosphorus-containing flame retardants

A method for producing compounds of formula (I) in which the radical R1 is selected from -NH2, -NH2-zAz, and monovalent alkyl and aryl radicals, the radicals A are selected in each case independently of one another from the phosphoryl radicals DOPO-, DPhPO- and DPhOPO-, and the indices x, y and z, in each case independently of one another, stand for 0 or 1, wherein at least one of the indices is ≠0, by reacting, in a first step, melamine or, when R1 is an alkyl or aryl radical, the corresponding alkyl or aryl guanamine, with one or more of the corresponding phosphinyl chlorides DOP-CI, DPhP-Cl and DPhOP-CI, in order to bond one or more phosphinyl radicals to the amino groups(s) of the melamine or guanamine, and in a second step oxidizing the phosphinyl radical(s) by reaction with an oxidizing agent to give the corresponding phosphoryl radical(s).