PPA 1.) 100 deg C, 1 h, 2.) 120 deg C, 15 min;

1: 73 percent / 10percent NaOH / ethanol / 2 h / Heating 2: 74 percent / polyphosphoric acid / 1.) 100 deg C, 1 h, 2.) 120 deg C, 15 min View Scheme

1: 73 percent / 10percent NaOH / ethanol / 2 h / Heating 2: 74 percent / polyphosphoric acid / 1.) 100 deg C, 1 h, 2.) 120 deg C, 15 min View Scheme