triethylamine in benzene 0.25 h;

1: 4-Methoxy-thiobenzoic acid S-(5,5-dimethyl-2-thioxo-2λ5-[1,3,2]dioxaphosphinan-2-yl) ester in benzene 1 h; Heating; 2: diethylamine in benzene cooling; Further stages.;