1: With oxalyl dichloride; dimethyl sulfoxide in dichloromethane T=-78°C; 0.5 h; 2: With triethylamine in dichloromethane T=-78 - 20°C;

Multi-step reaction with 3 steps 1.1: sodium hydride / 0 - 20 °C1.2: 20 °C1.3: 150 °C2.1: water; sodium chloride / dimethyl sulfoxide / 150 °C3.1: diisobutylaluminium hydride / tetrahydrofuran; toluene / -50 °C