A facile route to 4,4'-bipyrazole (H2bpz) and other symmetric bipyrazoles is achieved via the palladium-catalyzed homocoupling of a pyrazole boronic ester in the presence of air and water, enabling us to provide the first crystal structures and evidence of structural phase changes in the bipyrazolate-based metal-organic framework Co(bpz).
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http://dx.doi.org/10.1039/c9cc08614e | DOI Listing |
Molecules
August 2022
Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, 420008 Kazan, Russia.
Elaboration of a convenient route towards donor-substituted pyrazoles from heteropropargyl precursors is challenging due to a number of thermodynamically favorable side reactions (e.g., acetylene-allene isomerization and Glaser homocoupling).
View Article and Find Full Text PDFMolecules
December 2020
Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark.
Pyrazole, a member of the structural class of azoles, exhibits molecular properties of interest in pharmaceuticals and materials chemistry, owing to the two adjacent nitrogen atoms in the five-membered ring system. The weakly basic nitrogen atoms of deprotonated pyrazoles have been applied in coordination chemistry, particularly to access coordination polymers and metal-organic frameworks, and homocoupling reactions can in principle provide facile access to bipyrazole ligands. In this context, we summarize recent advances in homocoupling reactions of pyrazoles and other types of azoles (imidazoles, triazoles and tetrazoles) to highlight the utility of homocoupling reactions in synthesizing symmetric bi-heteroaryl systems compared with traditional synthesis.
View Article and Find Full Text PDFChem Commun (Camb)
January 2020
Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.
RSC Adv
March 2019
Institute of Pharmaceutical Chemistry, University of Szeged, Interdisciplinary Excellence Center Eötvös u. 6 H-6720 Szeged Hungary +36-62-545-705 +36-62-545-768 +36-62-545-562.
A flow chemistry-based approach is presented for the synthesis of 3,5-disubstituted pyrazoles sequential copper-mediated alkyne homocoupling and Cope-type hydroamination of the intermediary 1,3-diynes in the presence of hydrazine as nucleophilic reaction partner. The proposed multistep methodology offers an easy and direct access to valuable pyrazoles from cheap and readily available starting materials and without the need for the isolation of any intermediates.
View Article and Find Full Text PDFDalton Trans
September 2017
Departament de Química, Unitat de Química Inorgànica, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193-Bellaterra, Barcelona, Spain.
In this work, we describe the synthesis of a new N-heterocyclic carbene (NHC) ligand, derived from a hybrid pyrazole-imidazolium scaffold, namely 1-[2-(3,5-dimethylpyrazol-1-yl)ethyl]-3-((S)-1-phenylethyl)-3H-imidazol-2-ylidene (L). This ligand has been used as a stabilizer for the organometallic synthesis of palladium(0) nanoparticles (Pd NPs). L presents a better stabilizing effect than its pre-carbenic HLCl counterpart, allowing the formation of isolated Pd NPs while HLCl yields aggregated ones.
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