A mixture of tert-butyl 3-(aminocarbonyl)azetidine-1-carboxylate (156 mg, 0.779 mmol) and triethyloxonium tetrafluoroborate (280 mg, 1.5 mmol) in tetrahydrofuran (0.4 mL) was stirred at room temperature for 1 h and then concentrated. A mixture of {trans-4-[(6-aminothieno[3,2-b]pyridin-7-yl)amino]cyclohexyl}acetonitrile (39 mg, 0.14 mmol) and the above made reagent in ethanol (0.70 mL) was heated at reflux for 2 h. The mixture was cooled to room temperature, diluted with EtOAc, washed with sat. NaHCO3 solution, dried over MgSO4, concentrated and purified on silica gel column (0-5% MeOH in methylene chloride) to give the desired product. LCMS calculated for C24H30N5O2S (M+H)+: m/z=452.2. Found: 452.1.
