Red-Al → 4-(3,5-Difluoro-pyridin-2-yl)-piperazine-1-carboxylic acid tert-butyl ester
Reaction equation
[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][N:11]([C:14]2[C:19]([F:20])=[CH:18][C:17]([F:21])=[C:16](F)[N:15]=2)[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].COCCO[AlH2-]OCCOC.[Na+]>C1(C)C=CC=CC=1.[Cl-].[Cl-].C1([Ti+2]C2C=CC=C2)C=CC=C1>[C:1]([O:5][C:6]([N:8]1[CH2:9][CH2:10][N:11]([C:14]2[C:19]([F:20])=[CH:18][C:17]([F:21])=[CH:16][N:15]=2)[CH2:12][CH2:13]1)=[O:7])([CH3:4])([CH3:2])[CH3:3]Participants
Reactant 2
Product 1
Reagents, catalysts & solvents 2
Procedure
(Analogous to the procedure of Hee-Gweon Woo; Bo-Hye, Kim and Sun-Jung Song, Bull. Korean Chem. Soc. 1999, 20, 865-866). 4-(3,5,6-Trifluoro-pyridin-2-yl)-piperazine-1-carboxylic acid tert-butyl ester from step (a) above (950 mg, 3 mmol) was added to a mixture of bis(cyclopentadienyl)titanium dichloride (37 mg, 0.15 mmol, Aldrich) and Red-Al (1.32 mL, Aldrich) in toluene (3 mL). The reaction mixture was stirred at room temperature for 3 h and quenched by the addition of water (50 mL). The mixture was extracted with EtOAc (2×40 mL) and the combined organic phases were washed with brine (50 mL), dried over Na2SO4, and filtered. The filtrate was concentrated in vacuo and the residue was purified by silica gel chromatography, eluting with 20% EtOAc/hexane to give the title compound as a light-yellow oil. MS (ESI, pos. ion) m/z: 300 (M+1).
Workup
- customquenched by the addition of water (50 mL)
- extractionThe mixture was extracted with EtOAc (2×40 mL)
- washthe combined organic phases were washed with brine (50 mL)
- dry with materialdried over Na2SO4
- filtrationfiltered
- concentrationThe filtrate was concentrated in vacuo
- customthe residue was purified by silica gel chromatography
- washeluting with 20% EtOAc/hexane
Sources & evidence
- ORD record
- ord-d411c2838ff14a84aff82541adc2efab
- Source dataset
- uspto-grants-2011_09
- Patent number
- US08026241B2
Reaction notes
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