maleic anhydride; dihydrogen peroxide in chloroform 1.) room temperature, overnight; 2.) reflux, 5 h;

1: 82 percent / 90percent H2O2, maleic anhydride / CHCl3 / 1.) room temperature, overnight; 2.) reflux, 4 h 2: 89 percent / POCl3 / 0.5 h / Heating 3: 96 percent / 90percent H2O2, maleic anhydride / CHCl3 / 1.) room temperature, overnight; 2.) reflux, 5 h View Scheme

tetrakis(triphenylphosphine) palladium(0); potassium carbonate in N,N-dimethyl-formamide 6 h; Heating;

trichlorophosphate 0.5 h; Heating;