Cornforth reagent → toluene-4-sulfonic acid 5-acetyl-4-cyclopentyl-1H-pyrazol-3-yl ester
Reaction equation
[CH:1]1([C:6]2[C:7]([O:14][S:15]([C:18]3[CH:23]=[CH:22][C:21]([CH3:24])=[CH:20][CH:19]=3)(=[O:17])=[O:16])=[N:8][NH:9][C:10]=2[CH:11]([OH:13])[CH3:12])[CH2:5][CH2:4][CH2:3][CH2:2]1.[Cr](O[Cr]([O-])(=O)=O)([O-])(=O)=O.[NH+]1C=CC=CC=1.[NH+]1C=CC=CC=1>ClCCl>[C:11]([C:10]1[NH:9][N:8]=[C:7]([O:14][S:15]([C:18]2[CH:19]=[CH:20][C:21]([CH3:24])=[CH:22][CH:23]=2)(=[O:17])=[O:16])[C:6]=1[CH:1]1[CH2:5][CH2:4][CH2:3][CH2:2]1)(=[O:13])[CH3:12]Participants
4
Procedure
To toluene-4-sulfonic acid 4-cyclopentyl-5-(1-hydroxyethyl)-1H-pyrazol-3-yl ester (3.65 g, 10.43 mmol) in dichloromethane (250 ml) was added pyridinium dichromate (3.92 g, 1 molar eq) and the resulting slurry was stirred at room temperature for 1 h. The mixture was poured directly onto a column of silica gel, and the crude product was eluted off with ethyl acetate. Evaporation and further purification on silica gel using 0 to 20% ethyl acetate in isohexane as eluent yielded toluene-4-sulfonic acid 5-acetyl-4cyclopentyl-1H-pyrazol-3-yl ester as a colourless oil (1.36 g). 1H NMR (400 MHz, CDCl3) δ 1.62-1.91 (8H, m), 2.46 (3H, 8), 2.53 (3H, s), 3.26 (1H, m), 7.37 (2H, d, J=6.8 Hz), 7.90 (2H, d, J=6.8 Hz); MS (ES+) m/e 349 [MH]+.
Workup
- additionThe mixture was poured directly onto a column of silica gel
- washthe crude product was eluted off with ethyl acetate
- customEvaporation and further purification on silica gel using 0 to 20% ethyl acetate in isohexane as eluent
Sources & evidence
- ORD record
- ord-cfb77b20db63406c98f038bf80cf49fa
- Source dataset
- uspto-grants-2005_03
- Patent number
- US06872720B2
Reaction notes
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