2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 3-Tert-butyl-4-cyano-isoxazole-5-carboxylic acid ethyl ester

HRID 570198Notes

Reaction equation

[CH2:1]([O:3][C:4]([CH:6]1[O:10][N:9]=[C:8]([C:11]([CH3:14])([CH3:13])[CH3:12])[CH:7]1[C:15]#[N:16])=[O:5])[CH3:2].C(C1C(=O)C(Cl)=C(Cl)C(=O)C=1C#N)#N>C1(C)C=CC=CC=1>[CH2:1]([O:3][C:4]([C:6]1[O:10][N:9]=[C:8]([C:11]([CH3:13])([CH3:12])[CH3:14])[C:7]=1[C:15]#[N:16])=[O:5])[CH3:2]

Participants

Conditions

Temperature: 110 °C

Procedure

3-tert-Butyl-4-cyano-4,5-dihydro-isoxazole-5-carboxylic acid ethyl ester (1.51 g, 2.56 mmol corrected for the measured purity, prepared as described in the previous step) was dissolved in toluene (10 mL) and DDQ (2.41 g, 10.6 mmol) was added as a solid. The resulting mixture was heated to 110° C. for 16 h and then cooled to room temperature and diluted with hexanes (2 mL). The resulting suspension was filtered and the precipitate was washed once with toluene (4 mL). The filtrates were combined and concentrated under reduced pressure. The resulting residue was chromatographed on a 24-g SiO2 pre-packed column eluting with 0:1-1:4 EtOAc-hexanes to yield 3-tert-butyl-4-cyano-isoxazole-5-carboxylic acid ethyl ester. 1H-NMR (400 MHz, CDCl3) δ: 4.52 (q, J=7.1 Hz, 2H), 1.49 (s, 9H), 1.43-1.48 (t, J=7.1 Hz, 3H).

Workup

customprepared
temperaturecooled to room temperature
filtrationThe resulting suspension was filtered
washthe precipitate was washed once with toluene (4 mL)
concentrationconcentrated under reduced pressure
customThe resulting residue was chromatographed on a 24-g SiO2 pre-packed column
washeluting with 0:1-1:4 EtOAc-hexanes

Sources & evidence

ORD record: ord-4771b36d99a740d1847d928a81d205d0
Source dataset: uspto-grants-2015_05
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US09023846B2

Reaction notes

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