Yield given. Multistep reaction;

2: 61 percent / potassium tert-butoxide / hexamethylphosphoric acid triamide / 2 h / Ambient temperature 3: 1.) NaBH4, cerium (III) chloride hydrate, 2.) triethylamine, 2,4-dinitrobenzenesulfenyl chloride / 1.) methanol, 10 min, 2.) a) dichloromethane, -35 deg c, 0.5 h, b) RT, 3 h View Scheme

Multi-step reaction with 2 steps 1: 1.) lithium aluminium hydride, 2.) pyridine, p-toluenesulfonyl chloride / 1.) ether, 45 min, 2.) RT, 4 d2: 78 percent Chromat. / N-bromosuccinimide, benzoyl peroxide / CCl4 / 1.5 h / Heating  

Multi-step reaction with 3 steps 1: 1.) t-BuLi / 1.) hexane, THF, from -50 deg c to -20 deg C, 2.) THF, hexane, from -20 deg C to RT2: 1.) lithium aluminium hydride, 2.) pyridine, p-toluenesulfonyl chloride / 1.) ether, 45 min, 2.) RT, 4 d3: 78 percent Chromat. / N-bromosuccinimide, benzoyl peroxide / CCl4 / 1.5 h / Heating  

Multi-step reaction with 2 steps 2: 61 percent / potassium tert-butoxide / hexamethylphosphoric acid triamide / 2 h / Ambient temperature