Ligand-Dependent Site-Selective Suzuki Cross-Coupling of 4-Bromopyrazol-5-yl Triflates
Ligand-dependent Suzuki cross-coupling of 4-bromopyrazol-5-yl triflates has been developed. This approach enabled selective introduction of an aryl substituent at the C4 or C5 position in pyrazoles. This protocol is the first example in which the cross-coupling proceeded predominantly at the C4 position in pyrazoles, which is generally recognized as the least reactive position. The selection of phosphine ligands switched the order of arylation. This method should be highly useful for preparing diverse poly-substituted pyrazole derivatives.
Reactions of (E)-4-(p-Substitutedphenyl)-3-Phenyl-3-Buten-2-Ones with Hydrazine Derivatives
Reactions of (E)-4-(p-substitutedphenyl)-3-phenyl-3-buten-2-ones 1a-d with hydrazine hydrate, p-substituted aroylhydrazines and phenylhydrazine afforded the corresponding substituted azine 2a-d, the aroylhydrazone 3a-p as
Elba, M. E.,Darwish, A. I.,Mohamed, A. A.,El-Sadany, S. K.
p. 483 - 500
(2007/10/03)
Pyrazoles by Cyclisation of Benzoin Phenylhydrazone with Aldehydes
By fusing (E)- or (Z)-benzoin phenylhydrazone and aldehydes, 3-substituted 1H-pyrazoles (2) are obtained.The structure of 2d was confirmed by X-ray analysis.
Gnichtel, Horst,Brockmanns, Manfred,Salem, Widah I.,Luger, Peter
p. 589 - 592
(2007/10/02)
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