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

HRID 1481518Notes

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-b009a73e84644b1989cbeb8c078624fd
Source dataset: uspto-grants-2016_08
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US09409915B2

Reaction notes

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