Methanol → 5-(3,5-dimethylisoxazol-4-yl)-N'-hydroxy-1-(4-hydroxyphenyl)-3-methyl-1H-pyrazole-4-carboximidamide

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Reaction Conditions

Reaction Steps

A hydroxylamine solution was prepared. Hydroxylamine-HCl (26 mg, 0.37 mmol) and NaHCO3 (32 mg, 0.37 mmol) dissolved in water (0.2 mL), methanol (0.4 mL) was stirred 2 min until gas ceased to evolve, the mixture was filtered and degassed (N2). This was added to the 5-(3,5-dimethylisoxazol-4-yl)-1-(4-methoxyphenyl)-3-methyl-1H-pyrazole-4-carbonitrile (11 mg, 0.037 mmol) and stirred at 130° C. for 30 min in the microwave. EtOAc and brine were added and the phases were separated. Purification using preparative HPLC gave E1 5-(3,5-dimethylisoxazol-4-yl)-N′-hydroxy-1-(4-hydroxyphenyl)-3-methyl-1H-pyrazole-4-carboximidamide (2.52 mg, 7.71 μmol, 21%) ES/MS m/z: 328.19 (M+H), 326.22 (M−H); 1H NMR (acetone-d6, 500 MHz): 7.10 m 2H; 6.84 m 2H, 2.36 s 3H, 2.10 s 3H, 1.89 s 3H. Starting material 5-(3,5-dimethylisoxazol-4-yl)-1-(4-hydroxyphenyl)-3-methyl-1H-pyrazole-4-carbonitrile was recovered (0.99 mg, 3.36 μmol) as well as E2 5-(3,5-dimethylisoxazol-4-yl)-1-(4-hydroxyphenyl)-3-methyl-1H-pyrazole-4-carboxamide (3.22 mg, 0.01 mmol) ES/MS m/z: 313.17 (M+H), 311.22 (M−H); 1H NMR (acetone-d6, 500 MHz): 7.10 m 2H, 6.85 m 2H, 2.47 s 3H, 2.12 s 3H, 1.95 s 3H. Identification of Example 6 by 1H-NMR showed that the oxime product was a single isomer, but did not confirm whether the (E) or (Z) oxime isomer had been obtained.

Provenance & Evidence