3,5-tert-butylpyrazole

Tp )FeMe] [Tp = phenyltris(3-tert-butylpyrazol-l-yl)borate] (98JA10561) and [(> -Tp )FeR] [Tp = hydrotris(3,5-diisopropylpyrazol-l-yl)borate R = Ft, CH2CHCH2, CH2T0I-P] [98JCS(CC)973, 99JCS(CC)417] are prepared by methods similar to those described for the similar non-transition and late-transition metal alkyls. 

Scheme 7. Synthesis of bis(3,5-di-tert-butylpyrazol-l-yl)acetic acid Hbdtbpza (3c) (41).

The reaction of (3,5-di-tert-butylpyrazol-l-yl)(3, 5 -dimethylpyrazol-l-yl)acetic acid Hbpa (3d) with dimethyl zinc resulted in the chiral zinc methyl complex [Zn(bpa )(CH3)] (15) (Fig. 17) as racemic mixture (47). 

The reaction of magnesium bromide with potassium 3,5-di-tert-butylpyrazolate, K[Bu 2pz], in toluene affords Mg2(Bu 2pz)4 in THF the product is Mg2(Bu 2pz)4(THF)2." Both of these are dinuclear complexes with two bridging pyrazolato and two chelating ry -pyrazolato ligands. TMEDA binds to the unsolvated compound or displaces THF from the solvate to give Mg(Bu 2pz)2 (TMEDA), which is a mononuclear species with two ry -pyrazolates and chelating TMEDA. 

The methyne proton of tris(pyrazolyl)methane is sufficiently acidic to be removed by raBuLi, and the resulting reactive intermediate readily reacts with electrophiles. Klaui prepared two new anionic tripodal nitrogen water-soluble ligands (the lithium salts of tris(pyrazolyl)- and tris(3-tert-butylpyrazol)-methanesulfonic, Tpms and Tmps B" respectively) by addition of lithiated tris(pyr-azolyl)methane to a sulfur trioxide-trimethylamine complex (Scheme 25).146... 

Molecular structures of4-tert-butylpyrazoles. Trofimenko and co-workers reported an interesting study of the buttressing effects observed for three tert-huiy substituted pyrazoles in both the solution and solid state that employed X-ray crystallography and measurements. The authors found that the major tautomers in solution were consistent with the X-ray single crystal tautomeric preferences for the three analogues. The shifts shown... 

The flexible loop of AtHPPD allows C-terminal helix movement whereas the RnHPPD C-terminal helix is less flexible and caimot readily accommodate this rotation. The third important feature involves position and flexibility of the backbone near a proline residue which interacts with the pyrazole portion of the ligands. DAS869 and DAS645 with M-tert-butylpyrazoles butt up to AtPro259/RnPro239 and require rearrangement. In AtHPPD, the protein backbone shifts away to accommodate this bulky substitution. For RnHPPD it... 

Polynuclear Copper(l) Catalysts. Apart from mononuclear copper-catalyzed cyclopropanation, more recently polynuclear copper catalysts have been demonstrated to give characteristic diastereoselectivity. [Cu(dtbpz)]4, derived from 3,5-di-tert-butylpyrazole, gave high transicis ratio of 88 12 with slyrene and nonbulky EDA (19). In contrast, trinuclear triangular complexes, [Cu3( i3-OH)()u-pz)s(MeCOO)(MeO)(Hpz)] (Hpz = pyrazole), gave the same cyclopropanes in cis selectivity (trans cis = 38 62) (20). 

It has to be emphasized that the resulting bis(pyrazoI-l-yI)acetic acid Hbpza (3a) (Fig. 4) would not be available via the Otero route, since his synthesis is restricted to pyrazoles with substituents in 5-position of the p5rrazoIes. Other bis(pyrazoI-l-yI)methanes would be deprotonated at the CH2 bridge but also in position five of the pyrazole, due to ortho metallation. For the sterically more hindered bis(3,5-di-fert-butylpyrazole)acetic acid (3c) we followed Otero s synthetic pathway. In analogy to the synthesis of bis(3, 5-dimethylpyrazoI-l-yI)methane (2b) (72) 3,5-tert-butyIpyrazoIe... 

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