1: 85 percent / tetrahydrofuran / 0.5 h / Ambient temperature 2: 85 percent / DDQ, CSA / benzene / 5 h / Heating 3: 87 percent / 1N HCl / 12 h / Heating View Scheme

With  hydrogenchloride  1.) THF, RT, 30 min; 2.) THF, RT, 10 min;  Yield given. Multistep reaction;   

Multi-step reaction with 2 steps 1: 2.) 3 M HCl / 1.) THF, RT, 30 min; 2.) THF, RT, 10 min2: 85 percent / dl-10-camphorsulfonic acid (CSA), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) / benzene / 5 h / Heating