1: ethylene dibromide; dicyclohydroxymethylphosphine With 1,1,1,3,3,3-hexamethyl-disilazane T=100 - 110°C; silylation, phosphonylation; 4 h; 2: ethanol in water solvolysis; 0.5 h; Heating;

(i) PBr3, (ii) /BRN= 1730731/, (iii) /BRN= 1718733/; Multistep reaction;