Pyrazole-tethered arylphosphine ligands for Suzuki reactions of aryl chlorides: how important is chelation?

Mukherjee, Anuradha; Sarkar, Amitabha

doi:10.1016/j.tetlet.2004.11.016

Cited by 38 publications

(7 citation statements)

References 28 publications

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“…Pyrazole is a five-membered heterocyclic compound containing two nitrogen atoms. 1 The growth of pyrazole chemistry over the last 25 years has been significant, mainly as a result of the roles played by its derivatives in coordination chemistry as ligands 2 and in medicinal chemistry. For example, amino-pyrazole derivatives were found to be potentially useful in preventing brain-protein aggregation which is the first phase in the development of Alzheimer's disease.…”

Section: Introductionmentioning

confidence: 99%

Theoretical studies on proton transfer reaction of 3(5)-substituted pyrazoles

Chermahini

Teimouri

2014

J Chem Sci

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The inter and intra molecular proton transfer reactions of a series of pyrazole derivatives have been studied by using density functional theory (DFT) and MP2 methods implementing 6-311++G(d,p) atomic basis set. The substituents have been selected to cover a wide range of electronic effects. Proton transfer process was studied for mechanisms including single proton transfer, double proton transfer and proton transfer assisted by a water or ammonia molecule. The results showed single proton transfer reactions for interconversion pyrazole derivatives need highest activation energies in the range of 45.7−51.59 and 49.4−53.96 kcal/mol at B3LYP and MP2 levels, respectively. It was found that for the 3-substituted pyrazoles, electron withdrawing groups form stronger dimers but in the 5-substituted tautomers electron donating groups form stronger hydrogen bond. The double proton transfer reactions between dimers were studied and transition states calculated. The ranges of activation energies were found to be 17.51−19.36 and 17.02−17.80 kcal/mol for the C→E and D→D reactions respectively. In addition, the activation energies for the proton transfer reaction assisted by water or ammonia molecules were found to be in the range of 26.62−31.78 and 17.25−22.46 kcal/mol, respectively, calculated at MP2/6-311++G(d,p) level of theory.

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Section: Introductionmentioning

confidence: 99%

Theoretical studies on proton transfer reaction of 3(5)-substituted pyrazoles

Chermahini

Teimouri

2014

J Chem Sci

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“…A large number of metal complexes containing potentially hemilabile hybrid bidentate P−N donor ligands have been reported. − These studies have mainly focused on cases where the nitrogen donors are the sp 2 -N atom from pyridines , or oxazolines , and the P-donors are phosphines. Many late transition metal complexes (e.g., Ru, Rh, Pd, Ir) with mixed donor sp 2 -N−P ligands are efficient catalysts for a range of organic transformations including allylic substitutions, ,, hydrogenation, ,,− transfer hydrogenation, , and hydroboration. − , The chemistry of metal complexes with bidentate ligands with mixed pyrazolyl−phosphine metal donors has been, however, underexplored. − Examples of the application of pyrazolyl−phosphine donor ligands in homogeneous catalysis include palladium-catalyzed hydration of terminal alkynes, hydrosilylation of norbornene, allylic amination, , Suzuki reactions, nickel-promoted polymerization, and rhodium-catalyzed hydroboration. , …”

Section: Introductionmentioning

confidence: 99%

Rhodium(I) and Iridium(I) Complexes with Bidentate Phosphine−Pyrazolyl Ligands: Highly Efficient Catalysts for the Hydroamination Reaction

et al. 2007

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A range of rhodium(I) and iridium(I) complexes containing bidentate phosphine-pyrazolyl ligands of general formulas [M(R 2 PyP)(COD)]BPh 4 (R ) Me, iPr, Ph, M ) Ir, 3b-3d and M ) Rh, 4b-4d), [Ir(R 2 PyP)(CO) 2 ]BPh 4 (R ) Me, iPr, 5b,5c), and [M(R 2 PyP)(CO)Cl] (R ) Me, iPr, Ph, M ) Ir, 6b-6d and M ) Rh, 7b-7d) were successfully synthesized. A number of these complexes and their analogues with unsubstituted ligands are extremely active as catalysts for the intramolecular hydroamination of alkynes. The air-stable cationic iridium complexes containing 1,5-cyclooctadiene, COD, as co-ligands, [Ir(R 2 PyP)(COD)]BPh 4 (R ) H, Me, iPr, and Ph, 3a-3d), are efficient as catalysts for the cyclization of 4-pentyn-1-amine (8) to 2-methyl-1-pyrroline (9) with the turnover rate at 50% conversion (N t ) of up to 3100 h -1 , at 60°C. The cationic iridium complexes containing carbonyl co-ligands, [Ir(R 2 PyP)(CO) 2 ]-BPh 4 (R ) H, Me, iPr, 5a-5c), are moderately effective in catalyzing this reaction, and the neutral complexes [M(R 2 PyP)(CO)Cl] (M ) Ir, 6a Ir, 7a) are ineffective. Generally, an increase in steric bulk of the substituent R near the nitrogen donor leads to an improvement in catalytic performance of the resulting metal complexes.

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“…The first step of the process involves the insertion of a palladium species between a carbon-halogen bond -or a carbon-oxygen bond in some cases -through oxidative addition. The substrates most frequently used include aryl iodides, bromides and triflates; recently, however, aryl chlorides [3][4][5] have enabled great advances in this context by virtue of their being less expensive and readily available than the corresponding bromides and iodides. On the other hand, only a few, very recent references to Suzuki cross-coupling reactions involving aryl fluorides appear to exist [6][7][8].…”

Section: Introductionmentioning

confidence: 99%