1: thiophene-2-carboxylic acid With 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; triethylamine; 4-(N,N-dimethlyamino)pyridine in dichloromethane T=20°C; 2 h; 2: 4-oxo-piperidine in dichloromethane T=20°C; 18 h;

sodium hydroxide in toluene 0.5 h;