[Mg].II.Br[CH2:5][CH2:6]Br.Br[C:9]1[CH:17]=[C:16]([CH3:18])[C:12]([N:13]([CH3:15])[CH3:14])=[C:11]([CH3:19])[CH:10]=1.[P:20]([O-:27])(OCC)OCC>O1CCCC1.C1(C)C=CC=CC=1.O>[CH3:14][N:13]([CH3:15])[C:12]1[C:11]([CH3:19])=[CH:10][C:9]([PH:20](=[O:27])[C:9]2[CH:17]=[C:16]([CH3:18])[C:12]([N:13]([CH3:15])[CH3:14])=[C:11]([CH3:19])[CH:10]=2)=[CH:17][C:5]=1[CH3:6]
Under an argon atmosphere, a solution of magnesium (2.4 g, 0.75 equivalent), a small amount of iodine and a small amount of 1,2-dibromoethane in tetrahydrofuran (15 mL) was stirred at room temperature for 1 hr. A solution of 4-bromo-N,N,2,6-tetramethylaniline (31.2 g, 0.137 moL) synthesized in Reference Example 2 in tetrahydrofuran (50 mL) was added to the mixture at 25° C. to 30° C. over 1 hr, and the mixture was stirred at 40° C. for 1 hr. Then, a solution of diethyl phosphite (4.69 g, 0.25 equivalent) in tetrahydrofuran (15 mL) was added at 25° C. to 30° C. over 1 hr. Water (60 mL) was added to the mixture at 0° C. to 5° C., and then toluene (100 mL) was added to the mixture, and the insoluble material was removed by filtration. The filtrate was partitioned, and the organic layer was washed with water (30 mL) and concentrated under reduced pressure. The residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate) to give the title compound (4.6 g, colorless liquid). yield 40%.
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