4-Bromo-3,5-dimethyl-1-(THP)-1H-pyrazole

4-Bromo-3,5-dimethyl-1-(THP)-1H-pyrazole is a key intermediate for the preparation of 3,5‑dimethyl‑4‑aryl/heteroaryl‑1H‑pyrazoles, a scaffold frequently encountered in kinase inhibitors, phosphodiesterase inhibitors, and agrochemicals. The THP‑protected form of 4-Bromo-3,5-dimethyl-1-(THP)-1H-pyrazole is preferred over the free N–H pyrazole because it eliminates the acidic proton and prevents the formation of N‑arylated side products during Suzuki‑Miyaura or Buchwald‑Hartwig couplings. Process chemists value 4-Bromo-3,5-dimethyl-1-(THP)-1H-pyrazole as a bench‑stable, easy‑to‑handle liquid that can be directly charged into a reactor without pre‑activation. The bromine atom of 4-Bromo-3,5-dimethyl-1-(THP)-1H-pyrazole is sufficiently activated to undergo coupling under mild conditions (e.g., Pd(PPh₃)₄, K₂CO₃, dioxane/water, 80 °C), delivering biaryl products in high yield.

Product Parameters

Synthetic Route

4-Bromo-3,5-dimethyl-1-(THP)-1H-pyrazole is prepared by THP protection of 4‑bromo‑3,5‑dimethyl‑1H‑pyrazole. The pyrazole is dissolved in dichloromethane containing a catalytic amount of p‑toluenesulfonic acid or PPTS, and 3,4‑dihydro‑2H‑pyran is added dropwise. After stirring at room temperature until complete, the reaction is washed with sodium bicarbonate, dried, and concentrated. The crude product is purified by distillation or flash chromatography to give the title compound as a colorless oil.

FAQ

Q1: Can the THP group be removed under standard Suzuki coupling conditions?

A: The THP acetal is generally stable to the mildly basic conditions of Suzuki couplings. It can be removed afterwards by treatment with aqueous HCl in THF or methanol at room temperature.

Q2: What is the typical reactivity of the C4‑bromine?

A: It participates readily in Suzuki couplings with arylboronic acids at 80–100 °C using Pd(PPh₃)₄ or Pd(dppf)Cl₂ and aqueous carbonate bases.

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Looking for a reliable THP‑protected bromopyrazole to serve as your Suzuki partner? Get in touch with Cosperpharm’s heterocycle specialist — we can provide a retention sample, impurity profile, and volume quote within your required timeline.