1: potassium carbonate / acetone / 20 h / 50 °C 2: borane dimethyl sulfide complex; (S)-3,3-diphenyl-1-methyltetrahydro-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborol / tetrahydrofuran; toluene / 4 h / 0 - 20 °C 3: dipotassium hydrogenphosphate; 3-chloro-benzenecarboperoxoic acid / tetrahydrofuran / 2 h / 20 °C 4: potassium hydroxide / 5 h / 20 °C View Scheme