Stepwise Effective Molarities in Porphyrin Oligomer Complexes: Preorganization Results in Exceptionally Strong Chelate Cooperativity
摘要:
Complexes of zinc porphyrin oligomers with multivalent ligands can be denatured by adding a large excess of a monodentate ligand, such as quinuclidine. We have used denaturation titrations to determine the stabilities of the complexes of a cyclic zinc-porphyrin hexamer with multidentate ligands with two to six pyridyl coordination sites. The corresponding complexes of linear porphyrin oligomers were also investigated. The results reveal that the stepwise effective molarities (EMs) for the third through sixth intramolecular coordination events with the cyclic hexamer are extremely high (EM = 10(2)-10(3) M), whereas the values for the linear porphyrin oligomers are modest (EM approximate to 0.05 M). The speciation profiles for the denaturation reactions demonstrate that intermediate species are not significantly populated and that these equilibria are well described by a highly cooperative two-state model.
Stepwise Effective Molarities in Porphyrin Oligomer Complexes: Preorganization Results in Exceptionally Strong Chelate Cooperativity
摘要:
Complexes of zinc porphyrin oligomers with multivalent ligands can be denatured by adding a large excess of a monodentate ligand, such as quinuclidine. We have used denaturation titrations to determine the stabilities of the complexes of a cyclic zinc-porphyrin hexamer with multidentate ligands with two to six pyridyl coordination sites. The corresponding complexes of linear porphyrin oligomers were also investigated. The results reveal that the stepwise effective molarities (EMs) for the third through sixth intramolecular coordination events with the cyclic hexamer are extremely high (EM = 10(2)-10(3) M), whereas the values for the linear porphyrin oligomers are modest (EM approximate to 0.05 M). The speciation profiles for the denaturation reactions demonstrate that intermediate species are not significantly populated and that these equilibria are well described by a highly cooperative two-state model.
Construction of Heterobiaryl Skeletons through Pd-Catalyzed Cross-Coupling of Nitroarenes and Heterocyclic Arylborononate Esters with a Sterically Demanding NHC Ligand
作者:Wei Chen、Wanzhi Chen、Miaochang Liu、Huayue Wu
DOI:10.1021/acs.orglett.2c02796
日期:2022.9.30
cross-couplings of nitroarenes and heteroarylboronate esters has been developed. A number of heterobiaryl compounds containing pyridine, pyrimidine, quinoline, furan, thiophene, and pyrazole were prepared using [Pd(cinnamyl)Cl]2/2-aryl-5-(2,4,6-triisopropylphenyl)-2,3-imidazolylidene[1,5-a]pyridines as the catalysts in good to excellent yields. The synthetic practicality of this approach is demonstrated through
已经开发了钯催化的硝基芳烃和杂芳基硼酸酯的 Suzuki-Miyaura 交叉偶联。使用[Pd(肉桂基)Cl] 2 /2-芳基-5-(2,4,6-三异丙基苯基)-2,3-制备了许多含有吡啶、嘧啶、喹啉、呋喃、噻吩和吡唑的杂二芳基化合物咪唑亚基[1,5- a ]吡啶作为催化剂,收率良好。这种方法的合成实用性通过类药物分子的合成得到证明。
Application of hindered ether solvents for palladium catalyzed Suzuki–Miyaura, Sonogashira and cascade Sonogashira cross-coupling reactions
作者:Suwiwat Sangon、Nontipa Supanchaiyamat、James Sherwood、Duncan J. Macquarrie、Pakin Noppawan、Andrew J. Hunt
DOI:10.1039/d3ob00118k
日期:——
substrates, 71–89% in TMO and 63–92% in DEDMO. In addition, a Sonogashirareaction exhibited the excellent yields of 85–99% performed in TMO, which was significantly higher than traditional volatile organic solvents, THF or toluene, and higher than those reported for another non-peroxide forming ether, namely eucalyptol. Cascade Sonogashirareactions utilizing a simple annulation methodology were particularly
Stepwise Effective Molarities in Porphyrin Oligomer Complexes: Preorganization Results in Exceptionally Strong Chelate Cooperativity
作者:Hannah J. Hogben、Johannes K. Sprafke、Markus Hoffmann、Miłosz Pawlicki、Harry L. Anderson
DOI:10.1021/ja209254r
日期:2011.12.28
Complexes of zinc porphyrin oligomers with multivalent ligands can be denatured by adding a large excess of a monodentate ligand, such as quinuclidine. We have used denaturation titrations to determine the stabilities of the complexes of a cyclic zinc-porphyrin hexamer with multidentate ligands with two to six pyridyl coordination sites. The corresponding complexes of linear porphyrin oligomers were also investigated. The results reveal that the stepwise effective molarities (EMs) for the third through sixth intramolecular coordination events with the cyclic hexamer are extremely high (EM = 10(2)-10(3) M), whereas the values for the linear porphyrin oligomers are modest (EM approximate to 0.05 M). The speciation profiles for the denaturation reactions demonstrate that intermediate species are not significantly populated and that these equilibria are well described by a highly cooperative two-state model.