triphenylphosphine in chloroform a) -50 deg C, 15 min, b) to 20 deg C;

1: 1) O2, tetraphenyl phosphine; 2) conc. H2SO4 / 1) chloroform, -5 degC to 0 degC, irradiation 2: 27 percent / Ph3P / CHCl3 / -40 degC to room temp. View Scheme