iodine; triethylamine in ethyl acetate T=-10 - 5°C; 1 h;

1: 1.) thiourea, 2.) aq. NaOH / 1.) 180-200 deg C, 2.5 h, 2.) H2O, reflux, 2.5 h 2: 1.) N,N'-dicyclohexylcarbodiimide, 2.) K2CO3 / 1.) AcOEt, RT, 40 min, 2.) water, DMF, RT, overnight 3: 63.2 percent / I2, Et3N / ethyl acetate / 1 h / -10 - 5 °C View Scheme

1: 1.) N,N'-dicyclohexylcarbodiimide, 2.) K2CO3 / 1.) AcOEt, RT, 40 min, 2.) water, DMF, RT, overnight 2: 63.2 percent / I2, Et3N / ethyl acetate / 1 h / -10 - 5 °C View Scheme