and r 45 independently of one another denote hydrogen alkyl aryl halogen alkoxy aryloxy acyl or acyloxy preferably hydrogen methyl ethyl propyl or isopropyl or together with the substituted carbon atoms can form a saturated or unsaturated isocyclic or heterocyclic ring having 5 to 8 ring atoms r 46 denotes hydrogen alkyl aryl or alkyl or aryl substituted silyl preferably hydrogen and in addition the co catalysts used can be for example compounds of the formula r 51 and r 52 independently of one another denote hydrogen hydroxyl amino cyano halogen nitro alkylsulfonyl phenylsulfonyl alkyl sulfoxyl phenylsulfoxyl tosyl mercapto carboxyl halogeno carbonyl carboxyamide alkoxycarbonyl thiocarboxyamide alkyl aryl heteroaryl alkoxy aryloxy heteroaryloxy acyloxy alkylthio arylthio heteroarylthio acylthio acyl thioacyl or acylamino r 53 represents hydrogen or chlorine and in addition with one of the radicals r 51 or r 52 and together with the substituted carbon atoms can form an anellated saturated unsaturated or aromatic isocyclic or heterocyclic ring having 5 to 8 ring atoms r 54 denotes hydrogen alkyl aryl heteroaryl acyl thioacyl halogeno carbonyl or alkoxycarbonyl x 51 and x 52 independently of one another represent double bonded oxygen sulfur or r 57 substituted nitrogen where r 57 has the scope of the.