Oxygen → (R)-2-(6-Cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4yl)-pyridine 1-oxide

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Reaction Steps

100 mg (359 mmol) of 2-(6-cyano-2,2-dimethyl-2H-1-benzopyran-4-yl)pyridine 1-oxide, 9 ml of toluene, 1 ml of dichloromethane, 5.8 mg (14.4 mmol) of [Rh(COD)2 ]BF4 and 6.1 mg (14,4 mmol) of (R)-BIPHAS were placed in a 30 ml autoclave in a glove box (O2 content <1 ppm). The autoclave was sealed and the hydrogenation was carried out at 40° while stirring and a pressure of 40 bar. The hydrogenation was interrupted after 20 h. In order to determine the e.e. value and the conversion, a sample of the hydrogenation solution was evaporated and analyzed by HPLC on a chiral phase (Chiralcel OD-H). (R)-2-(6-Cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4yl)-pyridine 1-oxide was obtained in quantitative yield: e.e.=85%; chem. purity >99%.

Provenance & Evidence