Ethanol → Ethyl [(3S)-7-chloro-3,4-dihydro-2H-1,4-benzoxazin-3-yl]acetate

Participants

Reaction Conditions

Reaction Steps

Zinc trifluoromethanesulfonate (2.87 g, 7.91 mmol) was added to a well-stirred solution of (2E or Z)-(7-chloro-2H-1,4-benzoxazin-3(4H)-ylidene)acetate (Intermediate 19, 20 g, 79.1 mmol) in EtOH (150 mL, HPLC grade) at 20° C. The resulting mixture was evacuated and purged with N2 for several times, then (+)-1,2-bis(2s, 5s)-2,5-diphenylphospholanol ethane(1,5-cyclooctadiene) rhodium(I)tetrafluoroborate (0.51 g, 0.63 mmol) was added at 20° C. The resulting solution was evacuated and purged with N2 for several times again. Then the reaction was stirred at 60° C. for 16 h under H2 (15 bar pressure). The mixture was concentrated. The crude product was purified by silica gel column chromatography with EtOAc in PE from 0 to 20%. The pure product fraction was concentrated. This resulted in the title compound (18.9 g, 93.6%) as an orange oil.

Provenance & Evidence