A process for the preparation of bis-acylphosphanes of formula
R.sup.1P(COR.sup.2).sub.2 wherein R.sup.1 is unsubstituted phenyl or
phenyl substituted by one to five halogen, C.sub.1-C.sub.8-alkyl,
C.sub.1-C.sub.8-alkylthio and/or C.sub.1-C.sub.8-alkoxy; R.sup.2 is
C.sub.1-C.sub.18-alkyl or C.sub.2-C.sub.18-alkenyl;
C.sub.1-C.sub.18-alkyl or C.sub.2-C.sub.18-alkenyl substituted once or
more than once by halogen --OR.sup.10, --OCO--R.sup.10, --OCO-Hal,
--COO--R.sup.10, --N(R.sup.11)--CO--R.sup.10, --N(R.sup.11)--CO-Hal,
--CO--NR.sup.11R.sup.10, --CH.dbd.CH--CO--OR.sup.10 or
--CH.dbd.CH-phenyl;
--C(C.sub.1-C.sub.4alkyl)=C(C.sub.1-C.sub.4alkyl)-CO--OR.sup.10 or
--C(C.sub.1-C.sub.4alkyl)=C(C.sub.1-C.sub.4alkyl)-phenyl;
C.sub.5-C.sub.12cycloalkyl, C.sub.2-C.sub.18alkenyl,
phenyl-C.sub.1-C.sub.4alkenyl, phenyl, naphthyl, biphenyl or a 5- or
6-membered --O--, S-- or N-containing heterocyclic ring, the radicals
phenyl, naphthyl, biphenyl or the 5- or 6-membered -0-, S-- or
N-containing heterocyclic ring being unsubstituted or substituted by one
to five halogen, C.sub.1-C.sub.8alkyl, C.sub.1-C.sub.8alkoxy and/or
C.sub.1-C.sub.8alkylthio; the process comprises the steps in a) selective
reduction of dichlorophenylphosphanes of the formula R.sup.1P(CI).sub.2
by means of hydrogen at a temperature in the range from 20 to 200.degree.
C. and under hydrogen pressure of atmospheric pressure to 20 bar in the
presence of a hydrogenation catalyst, a tert. aliphatic amine or an
aromatic amine and in the presence of a non protic solvent which is
unreactive under the hydrogenation conditions to obtain cyclic
phenylphosphanes (R.sup.1P).sub.n (n=4 to 6); or b) selective reduction
of R.sup.1P(CI).sub.2 by means of hydrogen at a temperature in the range
from 80 to 250.degree. C. and under hydrogen pressure of 25 to 250 bar in
the presence of a hydrogenation catalyst, a tert. aliphatic amine or an
aromatic amine and in the presence of a non protic solvent which is
unreactive under the hydrogenation conditions to obtain R.sup.1PH.sub.2;
c) subsequent reaction with an acid halide of formula in the presence of
an apropriate base R.sup.2COHal wherein R.sup.2 is as defined above.
