The Mechanism of the Transition Metal-catalyzed Reaction of 1,1′-Carbonyldipyrazoles with Aldehydes and Ketones

Abstract

The metal-catalyzed reaction of 1,1′-carbonyldipyrazoles with aldehydes or ketones to give 1,1′-alkylidenedipyrazoles and carbon dioxide, the latter being derived from the amide carbonyl group as shown by labeling experiments, is sensitive to electronic and to steric substituent effects. Under comparable reaction conditions, 1,1′-carbonyldiimidazole, N-acetylpyrazole, and 1-pyrazole-N,N-diethylcarbonamide do not react with acetone while pyrazole-1-carbo(N′-phenylhydrazide) yields an anilino isocyanate dimer. These results are interpreted in terms of a mechanism that involves coordination of the metal ion at the 2,2′-nitrogen atoms of the pyrazole rings and heterolytic cleavage of an amide bond, followed by formation of a carbamate intermediate, decarboxylation, and metal ion exchange. Unsymmetrically substituted 1,1′-carbonyldipyrazoles were found to equilibrate thermally with their respective symmetrical analogs by an intermolecular exchange mechanism.

Redox‐Active p‐Quinone‐Based Bis(pyrazol‐1‐yl)methane Ligands: Synthesis and Coordination Behaviour

“…For the preparation of 2 a to 2 c, a synthetic protocol based on that of Peterson et al [41][42][43] was employed. Treatment of aldehydes 1 a to 1 c (Scheme 1) with bis(pyrazol-1-yl)methanone (1.2 equiv) in the presence of a catalytic amount of anhydrous CoCl 2 gave 2 a to 2 c in yields of between 23 and 36 %.…”

Reactivity of bis(pyrazol-1-yl)methanes functionalized by 2-hydroxyphenyl and 2-methoxyphenyl on the methine carbon atom with W(CO)5THF

“…no proton signal is observed for isomer 4A in the region markedly upfield relative to the phenyl group like those in isomer 4B and complex 5. However, the interconversion is observed in DMSO-d 6 .…”

Syntheses of bispyrazolyl monotriazolyl heteroscorpionate platinum(IV) complexes including an unusual Pt-CH2CH2-Pt bridge

“…The addition of thionyl chloride presumably generated the bispyrazolyl sulfonyl intermediate,3. Treating 3 with 1,2,3-triazole aldehyde 2-L1 and a catalytic amount of cobalt chloride [40][41][42] while refluxing overnight produced4-(bis(3,5-dimethyl-1Hpyrazol-1-yl)methyl)-1-phenyl-1H-1,2,3-triazole 4-L1in 87% yield, which we will abbreviate as bpztz Ph (eq 3). The analogous bpztz Cy ligand 4-L2 was produced in 56% yield while the bpztz C6F5 ligand 4-L3 was produced in 72% yield.…”