7,8-difluoro-3-methyl-2H-1,4-benzoxazine → (3S)-3-Methyl-7,8-difluoro-2,3-dihydro-4H-1,4-benzoxazine

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Reaction Steps

To an argon-purged pressure-resistant glass vessel (100 mL) equipped with a magnetic stir bar, RuCl[(R)-daipena][(R)-dm-segphos] (2.8 mg, 2.3 μmol) and KO(t-Bu) (13.2 mg, 0.118 mmol) were added, and the vessel was purged with argon again. To this vessel, a toluene (0.9 mL) solution containing 7,8-difluoro-3-methyl-2H-1,4-benzoxazine (84.9 mg, 0.464 mmol) and being degassed by the freeze-pump-thaw technique in advance was added by pressure transfer using a cannula. An operation in which hydrogen was introduced into the pressure-resistant vessel up to 0.8 MPa and then released was repeated 10 times to completely substitute the inside with hydrogen. Then, hydrogen was introduced up to 2.0 MPa, and the vessel was starred in a water bath at 40° C. for 23 hours. After hydrogen was released, the solution was concentrated under reduced pressure, and the residue was purified through a silica gel short path column (hexane:ethyl acetate=1:1) to obtain (S)-7,8-difluoro-3,4-dihydro-3-methyl-2H-1,4-benzoxazine (84.1 mg, 98%). A result of an analysis was conducted by high performance liquid chromatography (column: CHIRALCEL OD-H, mobile phase: hexane:IPA=98:2, 1 mL/min) showed that the optical purity of this product was 98% ee.

Provenance & Evidence