[Mg].[CH3:2]I.[CH2:4]([N:11]1[C:19]2[C:14](=[CH:15][C:16]([O:20][CH3:21])=[CH:17][CH:18]=2)[CH:13]=[C:12]1C(OCC)=O)[C:5]1[CH:10]=[CH:9][CH:8]=[CH:7][CH:6]=1.Cl.C(O[CH2:31][CH3:32])C>O1CCCC1.O.C(OCC)(=O)C>[CH2:4]([N:11]1[C:19]2[C:14](=[CH:15][C:16]([O:20][CH3:21])=[CH:17][CH:18]=2)[CH:13]=[C:12]1[C:31]([CH3:32])=[CH2:2])[C:5]1[CH:6]=[CH:7][CH:8]=[CH:9][CH:10]=1
8.95 g of magnesium was suspended in 160 ml of anhydrous diethyl ether. To the suspension was dropwise added 52.3 g of methyl iodide in 1 hour with stirring under refluxing. The resulting mixture was refluxed for 1 hour. Thereto was dropwise added a solution of 38 g of 1-benzyl-2-ethoxycarbonyl-5-methoxyindole dissolved in 110 ml of anhydrous tetrahydrofuran in 40 minutes at room temperature. The resulting mixture was refluxed for 1 hour and then cooled with ice cooling. Thereto was added 400 ml of ethyl acetate and to the resulting mixture was dropwise added 300 ml of water in 1 minute with stirring at 0° C. The resulting mixture was adjusted to pH 7.0 with diluted hydrochloric acid. The organic layer was separated, washed with an aqueous saturated sodium chloride solution and dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure. The residue was dissolved in 190 ml of methylene chloride. To the solution was added 29.8 g of triethylamine, and to the resulting mixture was dropwise added 16.9 g of methanesulfonyl chloride in 20 minutes with stirring at 0° C. The resulting mixture was stirred for 20 minutes at room temeprature. The reaction mixture was washed with 1N hydrochloric acid, an aqueous saturated sodium hydrogencarbonate solution and an aqueous saturated sodium chloride solution in this order and dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure. The residue was recrystallized from acetonitrile to obtain 26.8 g (yield: 79%) of 1-benzyl-2-isopropenyl-5-methoxyindole as light yellow crystals.
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