1: 98 percent 2: 95 percent / tetrahydrofuran / 0.25 h / -78 °C / -50 deg C, 10 min 3: 80 percent / tetrabutylammonium fluoride / tetrahydrofuran / 24 h / 25 °C 4: 88 percent / lithium, liquid NH3 / 2-methyl-propan-2-ol; tetrahydrofuran / 0.25 h / -78 °C 5: 57 percent / O2, sodium bicarbonate / Pt / acetone; H2O / 2 h / 57 °C View Scheme

With  dimethylboron bromide in  dichloromethane T=-78°C; 1 h;   

 

Multi-step reaction with 2 steps 1: 98 percent2: 95 percent / tetrahydrofuran / 0.25 h / -78 °C / -50 deg C, 10 min  

Multi-step reaction with 3 steps 1: 98 percent2: 95 percent / tetrahydrofuran / 0.25 h / -78 °C / -50 deg C, 10 min3: 80 percent / tetrabutylammonium fluoride / tetrahydrofuran / 24 h / 25 °C