1: With toluene-4-sulfonic acid in isopropyl mesylate 24 h; Heating / reflux; 2: With sodium methylate in isopropyl mesylate T=20°C; 72 h; Heating / reflux; 3: With acetic acid in isopropyl mesylate; water pH=5;

ammonium sulfate; formic acid; 1,1,1,3,3,3-hexamethyl-disilazane 1) 3 deg C, 1 h, 2) reflux, 5 h; Yield given. Multistep reaction;

hydrogenchloride