Hydrogen Peroxide → (S)-3-((S)-1-(4-bromophenyl)ethyl)-6-(2-hydroxy-2-methylpropyl)-6-phenyl-1,3-oxazinan-2-one

Participants

Reaction Conditions

Reaction Steps

To a 2.0 L 3-neck oven-dried RBF was charged the crude (S)-3-[(S)-1-(4-bromo-phenyl)-ethyl]-6-(2-methyl-oxiranylmethyl)-6-phenyl-perhydro-1,3-oxazin-2-one (G) and 750 mL of anhydrous tetrahydrofuran. The resulting solution was agitated and cooled to Tint=2-3° C. To the agitated clear solution was charged 1.0 M lithium triethylborohydride in tetrahydrofuran (Super Hydride, 348 mL, 348 mmol, 1.8 equiv). The addition is exothermic and addition controlled to maintain Tint=<8° C. The resulting solution was agitated at Tint=2-3° C. for 1.5 h and then allowed to warm to Tint=10-13° C. over a 2.5 h, which HPLC analysis indicates ˜94 A % (220 nm) conversion. To the agitated solution was charged a solution of hydrogen peroxide (95.7 mL of a 35 wt % aqueous solution diluted with 400 mL of water, 1.08 mol, 5.60 equiv). The addition is highly exothermic and addition controlled to maintain Tint=<25° C. The resulting solution was diluted with 1.00 L of methyl tert-butyl ether (MTBE) and washed with 1.00 L of water followed by 500 mL of a ˜30 wt % solution of sodium thiosulfate. The organic solution was dried with anhydrous sodium sulfate, filtered, and then concentrated via reduced pressure. The resulting material was subjected to flash silica chromatography (10-60% ethyl acetate, 600 g of silica) to produce 68 g of material consisting of both diastereomers (1.98:1 dr) and 41 g of the desired diastereomer (>99:1 dr). The material consisting of the mixed fractions was recrystallized from 250 mL of isopropyl acetate (IPAC) and 200 mL of heptane (anti-solvent) to produce upon filtration 31.3 g of product (95.7 A % at 220 nm, 74:1 dr). The two samples were combined to produce 72.3 g of product (83.6% yield for the two step operation). Analytical data for H: 1H-NMR spectroscopy (400 MHz, CDCl3) δ 7.37-7.29 (m, 5H), 7.25-7.21 (m, 2H), 6.82-6.79 (m, 2H), 5.61 (q, J=6.9 Hz, 1H), 2.83 (ddd, J=2.5, 5.4 and 11.6 Hz, 1H), 2.39 (ddd, J=5.7, 12.0 and 14.1 Hz, 1H), 2.27 (ddd, J=2.6, 4.8 and 14.0 Hz, 1H), 2.21-2.14 (m, 3H), 2.08 (s, 1H), 1.49 (d, J=7.0 Hz, 3H), 1.18 (s, 3H), 1.13 (s, 3H). 13C-NMR spectroscopy (100 MHz, CDCl3) δ 153.2, 142.6, 138.5, 131.6, 129.13, 129.10, 128.0, 125.3, 121.6, 84.2, 71.4, 54.1, 53.3, 36.4, 33.6, 32.1, 30.8, 15.6.

Provenance & Evidence