ozone in methanol T=-78°C; 0.25 h;

Multi-step reaction with 2 steps 1.1: NaH / dimethylformamide / 1 h / 0 °C1.2: 83 percent / dimethylformamide / 2 h / 20 °C2.1: 77 percent / (R,S)-norephedrine; BH3 / tetrahydrofuran / 48 h / 30 °C