Novel two step synthesis of pyrazoles and isoxazoles from aryl methyl ketones

Lin, Yang‐I; Lang, Stanley A.

doi:10.1002/jhet.5570140240

Cited by 118 publications

(43 citation statements)

References 2 publications

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“…The latter compound 2 was obtained from condensation of 1,4-diacetylbenzene with N,N-dimethylformamidine dimethylacetal [27,28]. For example, the reaction of the dienaminone 2 with 5 equivalents of acetamidine chloride (1a) in the presence of 5 equivalents of sodium ethoxide in boiling ethanol (for 18 h) afforded a solid with the empirical formula C 16 H 14 N 4 , and whose mass spectrum showed a strong molecular ion peak, as the base peak at m/z 262.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of some new 4,4′-(1,4-phenylene)dipyrimidine and 6,6′-(1,4-phenylene)-di(pyridin-2(1H)-one) derivatives

Shaker

2005

Heteroatom Chem.

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Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of some new 4,4′-(1,4-phenylene)dipyrimidine and 6,6′-(1,4-phenylene)-di(pyridin-2(1H)-one) derivatives

Shaker

2005

Heteroatom Chem.

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“…Ba[Cr(bpy)(ox) 2 ] 2 ·3H 2 O and bpp were synthesized according to previously described methods. [14,15] Physical Measurements: Dc magnetic susceptibility measurements were performed on polycrystalline samples using a magnetometer (Quantum Design MPMS-XL-5) equipped with a SQUID sensor. Variable-temperature measurements were carried out in the temperature range 2-400 K in a magnetic field of 0.1 T. The temperature sweeping rate was the same for the experiments performed on the original and methanol-solvated samples: 0.5 K·min -1 (2-10 K), 1 K·min -1 (10-50 K), 5 K·min -1 (50-200 K), 2 K·min -1 (200-400 K).…”

Section: Methodsmentioning

confidence: 99%

Structural Transformations and Magnetic Effects Induced by Solvent Exchange in the Spin Crossover Complex [Fe(bpp)₂][Cr(bpy)(ox)₂]₂

et al. 2005

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Keywords: Spin crossover / Iron / Solvent sensing / Hydration / Magnetic properties Structural, thermal, magnetic and solvent-exchange properties of the spin crossover compound [Fe(bpp) 2 ][Cr(bpy)(ox) 2 ] 2 containing paramagnetic anions are given. This complex salt 1 crystallises as a dihydrate with two inequivalent (high-spin and low-spin) Fe II sites. The dehydrated compound is a spincrossover material with T 1/2 Ȇ = 369 K and T 1/2 ȇ = 353 K. Rehydration takes place without loss of crystallinity, yieldingThe spin crossover between the diamagnetic low-spin (LS, S = 0) and the paramagnetic high-spin (HS, S = 2) states in iron(ii) complexes has attracted much interest. [1] Although the purely molecular origin of the effect is clearly established by its observation in solution, cooperativity plays a key role in the solid state, where the phenomenon may be accompanied by a structural phase transition. The transition is triggered by a given external perturbation (light irradiation, pressure or temperature change) and the response (change of the optical and magnetic properties) may be observed abruptly with a hysteretic behaviour. These materials can then be considered as bistable systems suitable for practical applications.In the search of increasing cooperativity, high-dimensional structures have been designed in which the functional molecular units are linked by bridging ligands.[2] Using this strategy, some nanoporous frameworks displaying spin crossover effects that are influenced by the reversible exchange of solvate molecules have been obtained.[3] Another approach relies on hydrogen bonding. In this context, the abrupt and hysteretic spin transitions of [Fe(bpp) 2 ]X 2 complex salts [bpp = 2,6-bis(pyrazol-3-yl)pyridine; X = anion] are well documented.[4] The amino groups of the pyrazolyl moieties can set up hydrogen bonds with its environment and this gives rise to a cooperative behaviour and a marked [a] dependence of the spin transition on the nature of the anion and the extent of hydration.[5] This family of compounds may provide good candidates for the study of solvation effects in spin crossover that can lead to interesting applications in molecular sensing. Further, these salts exhibit Light-Induced Excited Spin State Trapping (LIESST) effects at high temperatures with relatively long lifetimes of the photoinduced metastable states. [6] In this report, we give evidence for the strong dependence of the electronic configuration of the Fe 2+ cations on the exchange of guest solvent molecules in the salt [Fe(bpp) 2 ][Cr(bpy)(ox) 2 ] 2 (1) (bpy = 2,2Ј-bipyridine; ox = oxalate dianion). The complex anion has been chosen for its ability to form hydrogen bonds and π-π stacking interactions. [7] Compound 1 crystallises as a dihydrate [Fe(bpp) -complexes and water molecules. Two crystallographically independent octahedral iron(ii) sites, Fe(1A) and Fe(1B), were found ( Figure 1a). Both sites have a pseudo C 2v symmetry, with the tridentate bpp ligand binding to the iron ion in meridional positions. The Fe(1...

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“…Although several N-linked 2,6-bis(1 -pyrazolyl)pyridines were recently prepared by facile reactions of pyrazolate ions with pyridyl halides (4), the linkage in Scheme 1 (i.e., at the pyrazole 3-position) was dictated by a desire to apply the same methodology to develop both monotopic (X = N) and ditopic (X = CH) varieties of ligands. The parent 2,6-bis(3-pyrazoly1)pyridine has been prepared by a Mannich-type condensation (5). However, we additionally required substituents at the pyrazole 4-and 5-positions to ensure good liposolubility and poor solubility in water, and the Mannich reaction was not amenable to this.…”

Section: Introductionmentioning

confidence: 99%

Short syntheses of rigid acyclic or macrocyclic poly-imine ligands and their use in Ru(II), Fe(III), and alkali metal complexation

Dash¹,

Potvin²

1992

Can. J. Chem.

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ROBERT DASH and PIERRE G. POTVIN. Can. J. Chem. 70, 2249 (1992. Lipophilic derivatives of 2,6-bis(3-pyrazoly1)pyridine and 1,3-bis (3-pyrazoly1)benzene were obtained in acceptable yields by Stork reactions and transformed by N-alkylations into three pentadentates, three bis(bidentates), and one macrocyclic octadentate ligand. The parent bis(pyrazoly1) pyridine constituted a terpyridine analogue and readily formed a Ru(I1) complex. By comparison of 'H nuclear magnetic resonance patterns, it was found that the alkylations in the bis(pyrazoly1)pyridine series conferred an anti,anti conformation of the imino nitrogens. The pentadentates were then able to extract alkali metal ions into CHCI, with only modest strength and selectivity, but the preferred extraction of Li' by one of these was notable. By variation of the reaction conditions, a tri-iron(II1) and a di-iron(II1) complex were obtained from a bis(bidentate).ROBERT DASH et PIERRE G. POTVIN. Can. J. Chem. 70, 2249Chem. 70, (1992. Des derives lipophiles de la 2,6-bis(3-pyrazo1yle)pyridine et du 1,3-bis(3-pyrazoly1e)benzkne furent prepares en rendements acceptables par des reactions de Stork, puis N-alkylks pour fournir trois pentadentates, trois bis(bidentate) et un octadentate macrocyclique. En tant qu'analogue de la terpyridine, la bis(pyrazolyle)pyridine forma aisement un complexe au Ru(I1). D'aprks la resonance magnetique nuclkaire, les alkylations de la bis(pyrazoly1e)pyridine ont force l'adoption de conformations anti,anti et les pentadentates etaient donc de modestes recepteurs pour les cations alkalins et ont demontrk une faible sClectivit6 en extraction dans le chloroforme. Neanmoins, on souligne l'extraction preferentielle du Li' par l'un d'eux. Un bis(bidentate1 forma, selon les conditions employees, des complexes bi-et tri-nuclkaires avec le Fe(II1).

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Novel two step synthesis of pyrazoles and isoxazoles from aryl methyl ketones

Cited by 118 publications

References 2 publications

Synthesis and characterization of some new 4,4′-(1,4-phenylene)dipyrimidine and 6,6′-(1,4-phenylene)-di(pyridin-2(1H)-one) derivatives

Synthesis and characterization of some new 4,4′-(1,4-phenylene)dipyrimidine and 6,6′-(1,4-phenylene)-di(pyridin-2(1H)-one) derivatives

Structural Transformations and Magnetic Effects Induced by Solvent Exchange in the Spin Crossover Complex [Fe(bpp)₂][Cr(bpy)(ox)₂]₂

Short syntheses of rigid acyclic or macrocyclic poly-imine ligands and their use in Ru(II), Fe(III), and alkali metal complexation

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Novel two step synthesis of pyrazoles and isoxazoles from aryl methyl ketones

Cited by 118 publications

References 2 publications

Synthesis and characterization of some new 4,4′-(1,4-phenylene)dipyrimidine and 6,6′-(1,4-phenylene)-di(pyridin-2(1H)-one) derivatives

Synthesis and characterization of some new 4,4′-(1,4-phenylene)dipyrimidine and 6,6′-(1,4-phenylene)-di(pyridin-2(1H)-one) derivatives

Structural Transformations and Magnetic Effects Induced by Solvent Exchange in the Spin Crossover Complex [Fe(bpp)2][Cr(bpy)(ox)2]2

Short syntheses of rigid acyclic or macrocyclic poly-imine ligands and their use in Ru(II), Fe(III), and alkali metal complexation

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Structural Transformations and Magnetic Effects Induced by Solvent Exchange in the Spin Crossover Complex [Fe(bpp)₂][Cr(bpy)(ox)₂]₂