Pyrazole 3.4- trimethylene

Pyrazole, 3-(trifluoromethyl)-4,5-trimethylene as amebicide, 5, 291 Pyrazole, 3-triflyl-4-phenyl-synthesis, 5, 282 Pyrazole, 1,3,4-triiodo-synthesis, 5, 234 Pyrazole, 1,3,5-trimethyl-isomerization, 5, 221 Pyrazole, 3,4,5-trimethyl-bromination, 5, 240 halogenation, 5, 89 reactions... 

The tautomerism between 3-trifluoromethyl-5-methylpyrazole (44a) and 3-methyl-5-trifluoro-methylpyrazole (44b) has been discussed in detail <83IC774> the authors favor tautomer (44a). In the case of 3(5),4-polymethylenepyrazoles <91JHC647>, the position of the tautomeric equilibrium is directed by the Mills-Nixon effect thus, the 3,4-trimethylene tautomer (65b) is much more stable than the 4,5-one (65a) (AG = 1.3 kcal moU ) <94NJC269> (the x-ray structure of its hydrochloride has been determined <93Mi 30i-02 . The fact that campho[c]pyrazole (221) (see Section 3.01.10.1.2(ii)) exists in the solid state and in solution as the 2//-tautomer is another consequence of the Mills-Nixon effect <93AX(C)724>. 

The Buchner reaction resulted from his pioneering contribution to the reactions of arenes with a-diazoketones. Eduard Buchner (1860-1917) obtained his Ph.D. in Munich in 1888 under the supervision of Theodor Curtius (1857-1928). His graduate studies resulted in A New Synthesis of Trimethylene Derivetives, in which he demonstrated the existence of a cyclopropanol ring. As a postdoctoral researcher, Buchner synthesized pyrazole for the first time in 1891. Since then, Buchner had taken over and further developed the chemistry of doazoalkanes from his mentor Theodor Curtius. 

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