1: trifluoroacetic acid / CH2Cl2 / 3 h / Ambient temperature 2: triethylamine, 1-hydroxybenzotriazole, N,N'-dicyclohexylcarbodiimide / dimethylformamide / 23 h / 0 °C 3: 83 percent / tetrabutylammonium fluoride / dimethylformamide; tetrahydrofuran / 2 h / Ambient temperature View Scheme

piperidine; N,N-dimethyl-formamide 12 h; Ambient temperatureother reagent; Product distribution;