1.1: N-ethyl-N,N-diisopropylamine; O-(6-chloro-1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate / N,N-dimethyl-formamide / 16 h / 23 °C 2.1: piperidine / N,N-dimethyl-formamide / 0.5 h / 23 °C 3.1: silica gel / ethanol / 3 h / 90 °C 4.1: potassium tert-butylate / tetrahydrofuran / 0.5 h / -78 - 23 °C 4.2: 0.75 h / -10 °C 4.3: 2 h / 23 - 90 °C View Scheme

morpholine; sulfur in ethanol T=23 - 70°C; 12 h;