Isobutyryl chloride → ethyl (2R*)-2-(dibenzylamino)-4-methyl-3-oxo-pentanoate

HRID 530556Notes

Reaction equation

HRID 530556 reaction equation
[Li]CCCC.[CH2:6]([N:13]([CH2:20][C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1)[CH2:14][C:15]([O:17][CH2:18][CH3:19])=[O:16])[C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1.[CH3:27][CH:28]([CH3:32])[C:29](Cl)=[O:30]>C1COCC1>[CH2:20]([N:13]([CH2:6][C:7]1[CH:8]=[CH:9][CH:10]=[CH:11][CH:12]=1)[C@H:14]([C:29](=[O:30])[CH:28]([CH3:32])[CH3:27])[C:15]([O:17][CH2:18][CH3:19])=[O:16])[C:21]1[CH:22]=[CH:23][CH:24]=[CH:25][CH:26]=1

Participants

5

Reactant 3

HCID 62325Isobutyryl chlorideHCID 3553452Ethyl 2-(dibenzylamino)acetateHCID 178418339Butyllithium

Product 1

HCID 86699997ethyl (2R*)-2-(dibenzylamino)-4-methyl-3-oxo-pentanoateYield 116.1%

Reagents, catalysts & solvents 1

HCID 8028TetrahydrofuranSolvent2×

Procedure

In a round bottomed flask, at −78° C., under argon atmosphere, a solution of DIPA (1.6 ml, 9.3 mmol) in dry THF (40 ml) was treated with n-BuLi (2.5 M in n-hexane, 3.4 ml, 8.5 mmol). After 30 min a solution of ethyl 2-(dibenzylamino)-acetate [prepared as described in Example 47, step 1] (2.2 g, 7.8 mmol) in dry THF (40 ml) was added dropwise via cannula. After 15 min, 2-methyl-propanoyl chloride (2.4 mL, 23.3 mmol) was added dropwise at −78° C. and the mixture stirred for 10 min at rt. The reaction was then quenched with H2O, and Et2O was subsequently added. The organic layer was washed with brine, dried over Na2SO4, filtered, and concentrated in vacuo to give a crude product, as an oil. Purification by column chromatography using a Teledyne ISCO apparatus, eluting with Cy:AcOEt (98:2) gave a crude compound (3.2 g) as a mixture of two tautomers (ketone:enol=ca. 65:35), as a colorless oil, which was used without further purification in the following step. Ketone isomer: MS (ESI) m/z: 354 [M−H]+; (ESI) m/z: 352 [M−H]−. 1H NMR (DMSO-d6) δ 0.86 (d, J=6.73 Hz, 3H), 0.91 (d, J=7.01 Hz, 3H), 1.22 (t, J=7.11 Hz, 3H), 2.99 (hept, J=6.90 Hz, 1H), 3.78 (d, J=14.11 Hz, 2H), 3.84 (d, J=14.13 Hz, 2H), 4.10-4.24 (m, 2H), 4.29 (s, 1H), 7.17-7.48 (m, 10H). Enol isomer: MS (ESI) m/z: 354 [M−H]+; (ESI) m/z: 352 [M−H]−. 1H NMR (DMSO-d6) δ 0.48 (s, 3H), 0.50 (s, 3H), 1.43 (t, J=7.09 Hz, 3H), 3.16-3.28 (m, 1H), 3.90 (d, J=12.66 Hz, 2H), 3.96 (d, J=12.66 Hz, 2H), 4.38 (q, J=7.08 Hz, 2H), 7.10-7.46 (m, 10H), 12.32 (s, 1H).

Workup

  1. customThe reaction was then quenched with H2O, and Et2O
  2. additionwas subsequently added
  3. washThe organic layer was washed with brine
  4. dry with materialdried over Na2SO4
  5. filtrationfiltered
  6. concentrationconcentrated in vacuo
  7. customto give a crude product
  8. customPurification by column chromatography
  9. washeluting with Cy

Sources & evidence

ORD record
ord-409dcec562b340a497f1966c5dc21a7b
Source dataset
uspto-grants-2016_05
Patent number
US09353075B2

Reaction notes

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