1: 85 percent / 48percent hydrobromic acid / 1 h / Heating 2: 95 percent 3: 85 percent / pyridine / 1.) 0 deg C, 2 h, 2.) r.t., 24 h 4: 80 percent / tetrabutylammonium fluoride / acetonitrile / 3 h / Heating 5: 1.) methanesulfonic acid, 2.) hydrochloric acid / 1.) 100 deg C, 30 min, 2.) ethanol View Scheme