Substituted cyclic phosphine oxides

#This invention relates to new substituted cyclic phosphine oxides corresponding to the general formula (I): ##STR4## in which R.sup.1 represents an alkyl or an aryl radical having up to 14 carbon atoms,

#R.sup.2 r.sup.3 and R.sup.4 represent a C.sub.1 -C.sub.4 -alkyl radical, hydrogen, chlorine or bromine,

#R.sup.5 represents a C.sub.1 -C.sub.12 -alkyl radical and, where a = 0, an aryl radical and, where a = 1, 1/n of an n-valent cation, such as a metal, ammonium, guanidinium, phosphonium or hydrogen,

#The process according to the invention is illustrated by the following Examples:

#A total of 117 g of an approximately 1:1-mixture of 1-methyl-1-oxophospholine-2 and 1-methyl-1-oxophospholine-3 is added dropwise with intensive stirring over a period of 1 hour at a temperature of 113.degree. to 115.degree. C to 550 g of dimethyl phosphite accommodated in a 1 liter glass flask. At the same time, a suspension of 8 g of dibenzoyl peroxide in silicone oil is added dropwise over the reaction time. All the materials used have been freed from traces of oxygen by repeated evacuation and venting with nitrogen.

#On completion of the reaction, first the dimethyl phosphite and then the unreacted part of the 1-methyl-1-oxophospholine (81 g), which consists of substantially equal parts of the two isomers, are distilled off in vacuo. 28 g of an almost colorless oil (b.p. .sub.0.5 :185.degree. to 190.degree. C) distil over during distillation of the residue, thickening in the receiver into a white crystalline paste which becomes liquid again between 40.degree. and 55.degree. C.