3,5-Dimethylpyrazole is an organic compound with the formula (CH3C)2CHN2H. It is one of several isomeric derivatives of pyrazole that contain two methyl substituents. The compound is unsymmetrical but the corresponding conjugate acid (pyrazolium) and conjugate base (pyrazolide) have C2v symmetry. It is a white solid that dissolves well in polar organic solvents.
It is a precursor to a variety of ligands that are widely studied in coordination chemistry including trispyrazolylborate, a trispyrazolylmethane, and a pyrazolyldiphosphine.
Condensation of acetylacetone and hydrazine gives 3,5-dimethylpyrazole:
CH3C(O)CH2C(O)CH3 + N2H4 → (CH3C)2CHN2H + 2 H2OIt has found use as a blocking agent for isocyanates.
References
Reger, Daniel L.; Grattan, T.Christian; Brown, Kenneth J.; Little, Christine A.; Lamba, Jaydeep J.S.; Rheingold, Arnold L.; Sommer, Roger D. (2000). "Syntheses of tris(pyrazolyl)methane ligands and {[tris(pyrazolyl)methane]Mn(CO)3}SO3CF3 complexes: Comparison of ligand donor properties". Journal of Organometallic Chemistry. 607 (1–2): 120–128. doi:10.1016/S0022-328X(00)00290-4. /wiki/Doi_(identifier) ↩
Schenck, Terry G.; Downes, J. M.; Milne, C. R. C.; MacKenzie, Peter B.; Boucher, Terry G.; Whelan, John; Bosnich, B. (1985). "Bimetallic reactivity. Synthesis of bimetallic complexes containing a bis(phosphino)pyrazole ligand". Inorganic Chemistry. 24 (15): 2334–2337. doi:10.1021/ic00209a003. /wiki/Doi_(identifier) ↩
Johnson, William S.; Highet, Robert J. (1951). "3,5-Dimethylpyrazole". Organic Syntheses. 31: 43. doi:10.15227/orgsyn.031.0043. /wiki/Organic_Syntheses ↩
"Blocked Isocyanates" (PDF). Lanxess. June 2020. Archived (PDF) from the original on 2020-09-27. https://ure.lanxess.com/wp-content/uploads/sites/26/2020/07/Blocked-Isocyanates.pdf ↩