General procedure for the synthesis of 3-cyclopropylmethoxy-4-hydroxybenzaldehyde from 3-cyclopropylmethoxy-4-phenylmethoxybenzaldehyde: Unpurified 3-cyclopropylmethoxy-4-phenylmethoxybenzaldehyde was added directly to a 100 mL three-neck flask. Subsequently, ethyl acetate (EtOAc, 20 mL) and 10% Pd/C catalyst (136 mg, 0.13 mmol) were added. Hydrogen was introduced at room temperature and the reaction mixture was stirred for 2 h. The progress of the reaction was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the solvent in the filtrate was removed by distillation under reduced pressure to afford a light yellow oily liquid 3-cyclopropylmethoxy-4-hydroxybenzaldehyde (Z-5, 1.69 g, 92% yield).
