1.3.4- Trimethylpyrazole

The reaction was conveniently carried out in DME in the presence of benzophenone, and the yields were in the range 20-30%. In ethanol solution, 1,3,5-trimethylpyrazole (177 R = R = R = Me, R = H) yielded (183) and (184) (69T3287). In contrast with the previously observed sensitized photorearrangements (67HCA2244, 67CC488), this last reaction was not sensitized by acetophenone or benzophenone. 

Trimethylpyrazole 1.2.3.5- Trimethylpyrazolium Nitration occurs on the conjugate acid at the 4-position 71JCS(B)2365... 

Synthesis of the coumarin derivative 11.58 containing two isomeric triazolyl rings is indicated in Scheme 11.24- The substituted pyrazolyl derivative of naphthalimide 11.59 is prepared by a reaction sequence somewhat similar in principle to that already shown in Scheme 11.14, using 4-amino-1,3,5-trimethylpyrazole in the penultimate step followed by quaternisation. 

A catalytic amount of glacial acetic acid was added to a solution of diacetylpyridine (1 mmol) and 4-amino-1,3,5-trimethylpyrazole (4 mmol) in 10 ml of absolute ethanol and then refluxed 16 hours in a test tube containing a suspended Soxhlet thimble filled with activated 3A molecular sieves. The mixture was next concentrated, and an oily orange sohd was isolated. The crude material was triturated with petroleum ether, and the product was isolated as a sandy-colored solid. 

The Favorsky reaction should be considered a general method for producing pyrazolyl-a-acetylenic alcohols because even the less reactive 4-ethynyl-1,3,5-trimethylpyrazole, additionally deactivated by three donor methyl groups, reacts with acetone (Scheme 61). 

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