Compound 7 (CAS:1542705-83-8, 180 mg, 0.46 mmol) was used as a raw material and dissolved in a mixed solvent of ethanol (8 mL) and water (1 mL). Palladium acetate (Pd(OAc)2, 11 mg, 0.046 mmol), triphenylphosphine (PPh3, 14 mg, 0.053 mmol), and acetaldehyde oxime (53 mg, 0.92 mmol) were then added sequentially. The reaction mixture was heated to reflux for 2 hours. After completion of the reaction, the mixture was concentrated and the residue was purified by fast column chromatography (silica gel as stationary phase and dichloromethane/methanol=20:1 as eluent) to afford the target product 1-(4-(benzylamino)-7,8-dihydro-5H-pyrano[4,3-d]pyrimidin-2-yl)-2-methyl-1H-indole-4-carboxamide (II, 110 mg, Yield 58%). Mass spectrometry (LRMS) analysis of the product showed that the calculated value of (M+H)+ m/z was 414.19 and the measured value was 414.20. Nuclear magnetic resonance hydrogen spectrometry (1H-NMR, 300 MHz, D3COD) data were as follows: δ 7.72 (d, 1H), 7.44 (d, 1H), 7.41 (m, 1H), 7.31 (m, 3H), 7.25 (m, 1H), 6.96 (t, 1H), 6.77 (s, 1H), 4.71 (d, 2H), 4.63 (s, 1H), 4.05 (t, 2H), 2.11 (t, 2H), 2.45 (s, 3H).