The reaction mixture was allowed to slowly warm up to r.t. and stirred overnight. The obtained mixture was then cooled to 0 °C, and aq. NH4Cl (10 mL) was added dropwise. After additional stirring for 1 h, the resulting mixture was filtered, and the solution was concentrated under reduced pressure. The residue was mixed with H2O (5 mL) and the aqueous layer was extracted with EtOAc (3 × 5 mL). Combined organic layers was washed with brine (5 mL), dried with the anhydrous Na2SO4 and concentrated under vacuum. The obtained crude was used in the next step without purification.