p-Toluenesulfonic acid → Methyl 4-nitro-1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazole-3-carboxylate

Participants

Reaction Steps

A suspension of 4-nitro-1H-pyrazole-3-carboxylic acid methyl ester (1.3 g, Reference Example 55) and p-toluene sulfonic acid (144 mg) in chloroform (30 ml) at 0° C. was treated with 3,4-dihydropyran (1.04 ml) dropwise. The reaction mixture was allowed to warm to room temperature overnight. The reaction mixture was washed with saturated sodium bicarbonate (40 ml) and water (3×40 ml). The combined aqueous layers were extracted with dichloromethane (3×60 ml). The organic layers were combined, dried over magnesium sulfate and concentrated to yield 4-nitro-1-(tetrahydro-pyran-2-yl)-1H-pyrazole-3-carboxylic acid methyl ester (2.23 g) as a viscous brown oil. LC-MS (Method H): RT=2.79 minutes, 278.21 (M+H+Na)+. (b) 4-Formyl-1-(tetrahydro-pyran-2-yl)-1H-pyrazole-3-carboxylic acid ethyl ester

Provenance & Evidence