Selectfluor → 3-fluoro-1-(4-nitro-1H-pyrazol-5-yl)piperidin-4-one

Participants

Reaction Steps

FIG. 10 shows an exemplary synthesis of 3-fluoro-1-(4-nitro-1H-pyrazol-5-yl)azepan-4-amine 52 from 5-chloro-4-nitro-1H-pyrazole 3. Heating 3 with piperidin-4-one hydrochloride hydrate and potassium fluoride in a suitable solvent such as dimethylsulfoxide or using methods described in the literature gives 1-(4-nitro-1H-pyrazol-5-yl)piperidin-4-one 46. Heating 46 with trimethylsilyl chloride and triethylamine in a suitable solvent such as DMF or using methods described in the literature gives 1-(4-nitro-1H-pyrazol-5-yl)-4-(trimethylsilyloxy)-1,2,3,6-tetrahydropyridine 47. Fluorination of 47 using SelectFluor® in acetonitrile at a suitable temperature or using methods described in the literature gives 3-fluoro-1-(4-nitro-1H-pyrazol-5-yl)piperidin-4-one 48. Ring expansion of 48 to ethyl 6-fluoro-1-(4-nitro-1H-pyrazol-5-yl)-5-oxoazepane-4-carboxylate 49 may be achieved using ethyl diazoacetate and boron trifluoride diethyl etherate in a suitable solvent such as dichloromethane at suitable temperatures or using methods described in the literature. Decarboxylation of 49 by heating with hydrochloric acid at a suitable temperature or by methods described in the literature to give 3-fluoro-1-(4-nitro-1H-pyrazol-5-yl)azepan-4-one 50. Reductive amination of 50 by methods described in the literature gives 3-fluoro-1-(4-nitro-1H-pyrazol-5-yl)azepan-4-amine 51. The amine of 51 can be protected with a suitable protecting group such as trifluoroacetamide using trifluoroacetic anhydride with diisopropylethylamine in a suitable solvent such as dichloromethane, or using other methods described in the literature, to give amine-protected 52.

Provenance & Evidence