反应详情

To a 250 mL 3-neck round bottom flask equipped with magnetic stir bar, nitrogen inlet and thermocouple, is added tert-butyl (1S)-3-chloro-1-(3,5-difluorobenzyl)-2-oxopropylcarbamate (III, EXAMPLE 2, 4.4 g, 0.0132 moles, 1 equivalent) followed by THF (20 mL) and ethanol (30 mL) then cooled to −78°. Once the mixture is cooled, sodium borohydride (2.0 g, 0.0527 moles, 4 equivalents) is added as a solid portion wise over 30 min keeping the internal temperature below −70°. Once this addition is complete, the contents are stirred for 2 hr at −78° then warmed to 0° and stirred an additional 1 hr. The mixture is quenched by the addition of saturated potassium bisulfate (15 mL) and water (15 mL). This slurry is stirred for 30 min at 20-250 then concentrated under reduced pressure to half its volume. The mixture is then cooled to 0° and stirred for 30 min. After this time, the resultant solids are collected by filtration and washed with water (2×50 mL) then dried under reduced pressure at 50° to give crude product. A syn/anti ratio of 4-9:1 has been observed. The desired product is recrystallized from hexanes/ethanol (25/1) to give the title compound, mp=149°; NMR (DMSO-d6) δ 6.89-7.16, 5.61, 3.64-3.83, 3.19, 2.69 and 1.41; CMR (DMSO-d6) δ 163.67, 161.24, 155.44, 112.70, 101.55, 78.04, 72.99, 54.29, 48.24, 35.97 and 28.37.

1. customTo a 250 mL 3-neck round bottom flask equipped with magnetic stir bar, nitrogen inlet
2. temperaturethen cooled to −78°
3. temperatureOnce the mixture is cooled
4. customthe internal temperature below −70°
5. additionOnce this addition
6. temperaturethen warmed to 0°
7. stirringstirred an additional 1 hr
8. customThe mixture is quenched by the addition of saturated potassium bisulfate (15 mL) and water (15 mL)
9. stirringThis slurry is stirred for 30 min at 20-250
10. concentrationthen concentrated under reduced pressure to half its volume
11. temperatureThe mixture is then cooled to 0°
12. stirringstirred for 30 min
13. filtrationAfter this time, the resultant solids are collected by filtration
14. washwashed with water (2×50 mL)
15. customthen dried under reduced pressure at 50°
16. customto give crude product
17. customThe desired product is recrystallized from hexanes/ethanol (25/1)