dipyridinium dichromate in dichloromethane 20 h; Ambient temperature;

1: 65 percent / pyridinium dichromate / CH2Cl2 / 20 h / Ambient temperature 2: 41 percent / CuSO4 / methanol / 20 h View Scheme

1.1: 93 percent / PBr3 / diethyl ether / 0 °C 2.1: 63 percent / 160 °C 3.1: LDA / tetrahydrofuran; hexane / 15 h / -78 °C 3.2: 77 percent / tetrahydrofuran; hexane / -78 - 20 °C View Scheme