The general procedure for the synthesis of 6-iodo-3,4-dihydronaphthalen-1(2H)-one from 6-amino-1,2,3,4-tetrahydro-1-naphthalenone is as follows:[Synthesis Example 1 - Synthesis of Intermediates for Specific Compounds 1] Compound (2) was synthesized according to the formula of the reaction (Scheme).6-Amino-1,2,3,4-tetrahydro-1-naphthalenone (20 g, 119.0 mmol) Purchased from SIGMA Aldrich Co. and untreated before use. 6-Amino-1,2,3,4-tetrahydro-1-naphthalenone and 15% HCl (96 mL) were added to a 500 mL beaker. The aqueous sodium nitrite solution (9.9 g, 143.0 mmol dissolved in 42 mL of water) was added slowly and dropwise under the cooling of an ice bath, keeping the temperature of the reaction mixture below 5 °C. After the dropwise addition, the mixture was stirred at 0 °C for 30 min. Subsequently, a one-time addition of aqueous potassium iodide solution (23.7 g, 143.0 mmol dissolved in 77 mL of water) was added. The ice bath was removed and the reaction mixture continued to be stirred for 2.5 hours. Then, the mixture was heated to 60 °C maintained for 0.5 h until nitrogen gas stopped being produced. After completion of the reaction, it was cooled to room temperature and extracted three times with ether. The organic layer was washed sequentially with 5% aqueous sodium thiosulfate (100 mL x 3) and saturated brine (100 mL x 2). The organic layer was dried over sodium sulfate and filtered, and the filtrate was concentrated to obtain a red oil. The oily substance was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=9/1) to give a light orange solid. Further recrystallization with 2-propanol gave pale orange crystalline compound (2) (yield: 11.4 g, 35.2%). The structure of compound (2) was confirmed by the following analytical results: 1H NMR (500 MHz, CDCl3, TMS, δ): 2.13 (quintuple peak, 2H, J=5.7 Hz), 2.64 (t, 2H, J=6.3 Hz), 2.92 (t, 2H, J=6.0 Hz), 7.66 (d, 1H, J=8.0 Hz), 7.67 (s , 1H), 7.72 (d, 1H, J=8.0Hz); melting point: 74.0°C-75.0°C; mass spectrum: GC-MS m/z=272 (M+). The analytical results were consistent with the structure of compound (2).
