Reaktion #164476

Reaktionsgleichung

(R)-tert-butyl 2-(3,4-dichlorophenyl)-2-hydroxyethyl(2-hydroxyethyl)-carbamate

(2R,3R)-2,3-bis[(4-methylbenzoyl)oxy]butanedioic acid

isopropyl N-isopropoxycarbonyliminocarbamate

HCl

triphenylphosphine

→

(R)-2-(3,4-dichlorophenyl)morpholine (2R,3R)-2,3-bis[(4-methylbenzoyl)oxy]butanedioic acid salt

Ausbeute 22.4%

Lösungsmittel

acetic acid

MTBE

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeIn a 3 neck flask equipped with a mechanical stirrer
2. 2
   workup.ADDITIONthermocouple and addition funnel
3. 3
   workup.ADDITIONDuring the addition
4. 4
   Temperaturthe reaction temperature gradually increased
5. 5
   Temperaturto reflux
6. 6
   Temperaturthe mixture was chilled with an ice bath to 15° C
7. 7
   FiltrationThe resulting precipitate was filtered
8. 8
   Waschenthe filter cake was washed with 2 L of MTBE
9. 9
   EinengenThe filtrate was concentrated to approximately 2 L in vacuo
10. 10
    workup.STIRRINGthe mixture was stirred at 55° C. for 3 h
11. 11
    workup.STIRRINGto stir at RT for 10 h
12. 12
    Sonstigequenched with 1 L of 5M NaOH
13. 13
    SonstigeThe phases were separated
14. 14
    Waschenthe organic phase was washed with 1 L of brine
15. 15
    Einengenconcentrated in vacuo
16. 16
    Sonstigeaffording an oil which
17. 17
    SonstigeIn a 3 neck flask equipped with a mechanical stirrer
18. 18
    Temperaturthermocouple and heating mantle
19. 19
    workup.ADDITIONwas added crude yellow oil
20. 20
    Temperaturwas heated and to the mixture
21. 21
    Sonstigeaffording a white slurry
22. 22
    TemperaturThe mixture was heated
23. 23
    Temperaturto reflux
24. 24
    Sonstigeaffording a clear amber solution
25. 25
    Sonstigetransferred to a clean 5 L flask
26. 26
    Sonstigea course sparge tube as a filter
27. 27
    Temperaturto cool to −45° C. at ambient temperature
28. 28
    Temperaturcooled with an ice-bath to 12° C
29. 29
    FiltrationThe resulting mixture was filtered over a medium fritted funnel
30. 30
    Waschenwashed with 500 mL of glacial acetic acid
31. 31
    Filtrationfiltered
32. 32
    Sonstigedried

Vorschrift

In a 3 neck flask equipped with a mechanical stirrer, thermocouple and addition funnel using a water bath was added (R)-tert-butyl 2-(3,4-dichlorophenyl)-2-hydroxyethyl(2-hydroxyethyl)-carbamate (588 g, 1.679 mol) followed by MTBE (2.5 L). To the mixture was added triphenylphosphine (528 g, 467 mL, 2.02 mol) followed by isopropyl N-isopropoxycarbonyliminocarbamate (407 g, 390 mL, 2.02 mol) dropwise. During the addition, the reaction temperature gradually increased to reflux. The reaction mixture was allowed to stir at ambient temperature for 1 h. A precipitate occurred and the mixture was chilled with an ice bath to 15° C. The resulting precipitate was filtered, and the filter cake was washed with 2 L of MTBE. The filtrate was concentrated to approximately 2 L in vacuo and returned to the reaction vessel. HCl (1.26 L of 4 M in dioxane, 5.04 mol) was added and the mixture was stirred at 55° C. for 3 h. Effervescence occurred. The mixture was allowed to stir at RT for 10 h and quenched with 1 L of 5M NaOH. The phases were separated and the organic phase was washed with 1 L of brine, and concentrated in vacuo affording an oil which was 98% ee (chiral HPLC). In a 3 neck flask equipped with a mechanical stirrer, thermocouple and heating mantle was added crude yellow oil using glacial acetic acid (2.5 L) The solution was heated and to the mixture was added (2R,3R)-2,3-bis[(4-methylbenzoyl)oxy]butanedioic acid (649 g, 1.68 mol) affording a white slurry. The mixture was heated to reflux affording a clear amber solution. The mixture was vacuum transferred to a clean 5 L flask using a transfer tube and a course sparge tube as a filter. The mixture was seeded and allowed to cool to −45° C. at ambient temperature and then cooled with an ice-bath to 12° C. The resulting mixture was filtered over a medium fritted funnel and washed with 500 mL of glacial acetic acid. The filter cake was slurried with MTBE (500 mL twice), filtered and dried affording (R)-2-(3,4-dichlorophenyl)morpholine (2R,3R)-2,3-bis[(4-methylbenzoyl)oxy]butanedioic acid salt (233 g) as a white solid. The combined mother liquors were concentrated to 2 L in vacuo. The solution was allowed to sit for 12 h, filtered and the filter cake washed with 1 L of MTBE. This afforded an additional 186 g of product for a total of 419 g (40%, >99% ee) of product. To prepare the free base, the salt (178 g, 288 mmol) was added to a 2 L Erlenmeyer flask and diluted with 1 L of MTBE. 2M NaOH (400 mL) was added and the mixture was stirred until clear. The organic phase was separated and the aqueous phase was extracted with 500 mL of MTBE. The combined organic phases were dried over MgSO4 and concentrated in vacuo to afford the free base (R)-2-(3,4-dichlorophenyl)-morpholine (66 g, 100%) as a colorless oil. 1H-NMR (400 MHz, CDCl3) δ 7.50-7.49 (m, 2H), 7.19 (dd, J=1.6, 8.3 Hz, 1H), 4.47 (dd, J=2.4, 10.4 Hz, 1H), 4.09 (s, 1H), 4.08 (dd, J=1.9, 12.9 Hz, 1H), 3.82-3.75 (m, 1H), 3.09 (dd, J=2.5, 12.5 Hz, 1H), 2.97 (dd, J=3.1, 10.2 Hz, 2H), 2.72-2.69 (m, 1H). LC/MS (10%-99% CH3CN (0.035% TFA)/H2O (0.05% TFA)), m/z: M+1 obs=232.3; tR=0.67 min. Chiral HPLC (Astec Chirobiotic V2 column (25 cm×4.6 mm, 5 um), 100% methanol (0.1% NH4TFA, 1.5 mL/min) tR (R)=10.81 min; tR (S)=13.65 min.

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