Water → (R)-(-)-3,4-Dihydro-2-(4-methoxybenzyl)-2H-benzopyran

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Reaction Conditions

Reaction Steps

(R)-(-)-3,4-Dihydro-2-trifluoromethanesulfonyloxymethyl-2H-benzopyran (23.0 g, 78 mmol) and copper (I) bromide dimethyl sulfide complex (2.8 g, 13 mmol) were dissolved in tetrahydrofuran (400 ml) under a nitrogen atmosphere and cooled to -10° C., 4-Anisylmagnesium bromide (215 ml of a 1M solution in tetrahydrofuran, 0.215 mol) was added dropwise over 30 minutes, keeping the temperature below -5° C. The solution was stirred for 3 hours at 0° C. and then slowly poured into a mixture of water (800 ml) containing ammonium chloride (96 g, 1.8 mol) and methylene chloride (400 ml). The layers were separated and the aqueous portion was extracted with methylene chloride (400 ml). The combined organics were washed with 10% ammonium chloride (2×400 ml), water (250 ml), and brine (250 ml). The methylene chloride layer was dried (MgSC4), filtered and concentrated in vacuo. The residue was purified on silica gel using hexanes/methylene chloride (1:1) as eluent to afford 18.5 g (92% yield) of the title product as an oil. [α]D -99.2° (c 1.7, MeOH); 1H NMR (300 MHz, CDCl3) δ1.6-1.7 (m, 1H), 1.9-2.0 (m, 1H), 2.7-2.8 (m, 3H), 3.1 (dd, 1H), 3.8 (s, 3H), 4.1 (m, 1H), 6.8 (m, 3H), 7.0 (m, 2H), 7.2 (m, 2H) .

Provenance & Evidence