To a solution of N′-(4-azido-1-phenylbutylidene)-5-chloro-2-methyl benzohydrazide (100 mg, 0.28 mmol) in pyridine (1 mL) was added pivaloyl chloride (70 μL, 0.56 mmol). After stirring at room temperature for 16 hours the heterogeneous mixture was treated with water (10 mL) and extracted with EtOAc (3×10 mL). The combined organic phases were washed successively with 10% NaHSO4 (2×10 mL), NaHCO3 (10 mL) and brine (10 mL) then dried over Na2SO4 and concentrated. The residue was purified by preparative TLC (9:1 hexanes/EtOAc) to afford the product (62 mg, 50%) as a colorless oil.
