Aryl phosphonites, a process for their production and their use for stabilizing plastics

A process for the preparation of aryl phosphonites of the formula (V)

• in which A is non-existent or a direct bond or a divalent hydrocarbon bridge having 1 to 6 carbon atoms which may be substituted by groups mentioned further below under R.sup.1, or is a hetero atom, cycloalkylidene having 4 to 8 carbon atoms or phenylalkylidene having 7 to 12 carbon atoms, n is 1 or 2, R.sup.1 as monovalent radical is a non-aromatic hydrocarbon radical having 1 to 18 carbon atoms, a phenyl or benzyl radical, each of which can carry 1 to 3 substituents, or is .alpha.-methylbenzyl, .alpha.,.alpha.-dimethylbenzyl, naphthyl or a naphthyl radical carrying 1 to 5 substituents, in which the substituents are identical or different and are a non-aromatic hydrocarbon radical, an alkoxy radical, an alkylthio radical or a dialkylamino radical, in which the alkyl radicals each have 1 to 8 carbon atoms, aryl or aryloxy each having 6 to 10 carbon atoms or halogen having an atomic number from 9 to 35, and as divalent radical a phenylene radical which is unsubstituted or is substituted by up to 2 non-aromatic hydrocarbon radicals each having 1 to 8 carbon atoms or a naphthylene radical which is unsubstituted or carries 1 to 4 non-aromatic hydrocarbon radicals each having 1 to 8 carbon atoms as substituents;
• or, if both phenyl radicals are bonded via A, can also be biphenylene,
• R.sup.2 is a non-aromatic hydrocarbon radical having 1 to 18 carbon atoms, aryl, arylmethyl, arylethyl or arylisopropyl, in which the aryl in each case contains 6 to 10 carbon atoms, and
• R.sup.3 is hydrogen or a group mentioned under R.sup.2,
• which comprises reacting in a first step a hydrocarbon halide R.sup.1 (-Hal).sub.n, in which R.sup.1 has the above-mentioned meaning, n is=1 or 2 and the halogen has an atomic weight of at least 35, under Grignard conditions with at least molar amounts of magnesium to give the corresponding Grignard compounds R.sup.1 (MgHal).sub.n and reacting these in a second step with bisaryl halophosphonites of the formula VI ##STR4## in which A, R.sup.2, R.sup.3 and Hal have the above-mentioned meaning, with the formation of the aryl phosphonites (V).