反应详情

To 12 mL (24 mmol) of 2M allylmagnesium chloride in tetrahydrofuran, cooled in an ice bath, was added, with stirring, a solution of 4.95 g (14.98 mmol) of rac-2-chloro-3,4-dihydro-2,5,7,8-tetramethyl-6-(phenylmethoxy)-2H-1-benzopyran in 60 mL of anhydrous ether. The reaction mixture was stirred at 0° C. for 6 hr then worked up by being poured into cold, saturated NH4Cl solution and ether extraction. The product (5.4 g of a pale-yellow oil) was dissolved in 40 mL of methanol and 10 mL of ether containing 10 mg of p-toluenesulfonic acid monohydrate. The solution was stirred at room temperature for 21 hr then concentrated in vacuo. The residue was chromatographed on 75 g of silica gel. Elution with 40:1 parts by volume hexane-ether gave 2.88 g (57.2% yield) of rac-3,4-dihydro-6-(phenylmethoxy)-2-(2-propenyl)-2,5,7,8-tetramethyl-2H-1-benzopyran as a colorless oil.

1. additionwas added
2. stirringThe reaction mixture was stirred at 0° C. for 6 hr
3. additionby being poured into cold,
4. extractionsaturated NH4Cl solution and ether extraction
5. dissolutionThe product (5.4 g of a pale-yellow oil) was dissolved in 40 mL of methanol
6. stirringThe solution was stirred at room temperature for 21 hr
7. concentrationthen concentrated in vacuo
8. customThe residue was chromatographed on 75 g of silica gel
9. washElution with 40:1 parts by volume hexane-ether