p-t-Butylcalix[4]arene tetra-acetamide: a new strong receptor for alkali cations [1]

From the reaction ofp-t-butylcalix[4]arene with -chloro-N,N-diethyl acetamide a new lipophilic ether-amide ligand (2) has been obtained in high yield. Solution studies show (2) to be a very strong cation receptor for alkali cations, especially sodium and potassium. The X-ray crystal structure determination of the free ligand (2) and two potassium complexes (KI and KSCN) shows the calix[4]arene in a fixed cone structure and the cation completely encapsulated in a polar cavity of eight oxygen atoms. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82059 (57 pages).Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Lower Rim Substituted tert-Butyl calix[4]arenes (I). The Structure and Complexing Properties in Ion-Selective PVC Membrane Electrodes

Some di- and tetraamide tert-butylcalix[4]areneswere synthesized and described. Their ionophoric properties were studied in liquid membrane ion-selective electrodes. The correlation between thechemical structure (conformation in solution determined by ¹H NMR) and potentiometric ion-selectivity and complex formation constant havebeen studied. The PVC membrane electrodes based on tetraamides 8–11 show high sodium selectivity, are stable and long lasting. Disubstituted amides 1–7 are selective for larger and more lipophilic ions, as for exampleguanidinium ion. The crystal structure of the diamide 4 was determined by single crystal X-ray analysis. Crystals of 4 are triclinic, spacegroup P-1, with: a = 16,669(8), b = 17.795(10), c = 20.984(8) Å, =91.08(4)°, = 91.60(3)°, = 90.73(4)° and Z = 4. Ionophore 4 posseses a distorted cone conformation and is substituted at the proximal phenol rings.     

Theoretical calculations of95Mo-NMR chemical shifts for compounds [MoO4−n S n ]2−

Summary Theoretical calculation of⁹⁵Mo-NMR chemical shifts for [MoO_4–n S _n ]^2– (n=0–4) compounds is reported here for the first time on the basis of Fenske-Hall method and Sum-Over-State (SOS) perturbation theory. A systematic decrease in shielding of⁹⁵Mo nuclei with increase of number of sulfur in [MoO_4–n S _n ]^2–, which is observed experimentally, can be reasonably explained by our calculation. A good linear relationship between chemical shifts of calculation and experiment is obtained. The electronic structure and bonding in these compounds are also discussed.Supported by Nature Science Foundation of China     

Dibutylphosphinoylmethyloxythiacalix[4]arenes. Synthesis,structure, americium,europium and technetium extraction

A series of thiacalix[4]arenes bearing one, two or four chelating dibutylphopshinoylmethoxy groups have been synthesised and studied in the context of this paper. The synthesis consisted of precise Williamson alkylation of thiacalixarene tetrols with tosylate of dibutylhydroxymethyl phosphine oxide in the presence of alkali metal carbonates or sodium hydride. Stereochemical yield of the reaction (cone or 1,3-alternate conformer) depends on the nature of alkali metal. Small-sized ‘hard’ sodium cation organises the macrocyclic platform in the cone conformation, but larger and ‘soft’ potassium and cesium cations stabilise the macrocycle in the 1,3-alternate conformation. All synthesised compounds (except monophosphine monoxide) possess either moderate or high extraction ability towards pertechnetate ion. The cone-shaped thiacalix[4]arene tetraphosphine tetraoxide due to cooperative (macrocyclic) effect of eight oxygen atoms of the phosphinoylmetoxy-binding groups effectively extract spherical americium, europium cations due to cooperative (macrocyclic) effect of eight oxygen atoms of the phosphinoylmetoxy-binding groups. The extraction ability is very similar to that of calix[5]arene pentaphosphine pentaoxide existing in the cone conformation.     

Mixed ``Amide-phosphoryl' Calix[4]arenes. On the Selectivity of Two Conformers Towards Alkali Ion Complexation

The binding properties of cone-5,11,17,23-tetra-tert-butyl-25,27-bis(diethylcarbamoyl-methoxy)-26,28-bis(diphenylphosphinoylmethoxy)calix[4] arene (cone-1) towards alkali metals have beencompared with those of the corresponding partial-cone conformer (paco- 1). Bothhybrid ligands form stable complexes with alkalipicrates in tetrahydrofuran having a 1 : 1cation/ligand ratio. Regarding extractability, thatpresented by cone-1 decreases continuallyon-going from Li/Na to Cs, while that for paco-1 presents a peak selectivity for Na (withthe following order Na > K > Rb > Li > Cs).These selectivities parallel, respectively, resultsobtained for extraction and transport experiments. Thekinetics of the alkali metal thiocyanate transportthrough a bulk liquid membrane containing theseligands in 1,2-dichloroethane could be rationalised interms of a simple mathematical model. The lowertransfer coefficients found for paco-1 relative to cone-1 reflect the larger sizeof the diffusing paco-complex.     

Hard–Soft Receptors, Tetrakis[(N,N-diethylaminocarbonyl)methoxy] thiacalix[4]arene Derivatives with cone and 1,3-alternate Conformation

Direct O-alkylation of p-tert-butyltetrathiacalix[4]arene with N,N-diethylchloroacetamide afforded two conformational isomers (1,3-alternate and cone) of tetrakis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene and 1,3-disubstituted bis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene, depending on the base used. The complaxation behaviors of the tetrakis isomers were assessed by ¹H NMR titration experiments. Evidence of 1:2 (homo- and hetero-dinuclear) complexes formation of 1,3-alternate-tetrakis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene with alkali (K⁺ and Na⁺) or transition (Ag⁺) metal ions was obtained. Interestingly, it was found that the cone-tetrakis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene required a prior Ag⁺ complexation to form 1:2 heterodinuclear complex. Received in final form: 26 January 2005     

Synthesis, Conformational Studies and Inclusion Properties of Tetrakis[(2-pyridylmethyl)oxy]thiacalix[4]arenes

An attempted O-alkylation of the flexible macrocycle 1with 2-(chloromethyl)pyridine in the presence of Cs₂CO₃ under THF reflux afforded a mixture of twoconformers of tetra-O-alkylated product 4a in a ratio of 91:9 (cone-4a:1,2-alternate-4a)in 70% yield, while other possible isomers were not observed. In the case of Na₂CO₃, there was no reaction product,only the starting compound 1, whereasonly monoalkylated compound 3 was obtained when usingK₂CO₃ as the base. The distribution of cone conformer decreased in the case of O-alkylation of tetraol 1with 4-(chloromethyl)pyridine or benzyl bromide in the presence of Cs₂CO₃ in comparison with that ofO-alkylation with 2-(chloromethyl)pyridine, while the 1,2-alternate conformer increased in the same sequence. The larger Cs⁺might increase the contribution of the metal template effect, which can hold the 2-pyridylmethyl group(s) and theoxide group(s) on the same side of the tetrathiacalix[4]arene 1 through the cation-O^- and -N-interaction in the caseof O-alkylation of tetraol 1 with 2-(chloromethyl)pyridine.Only when the template metal can hold the 2-pyridyl group(s) andthe oxide group(s) on the same side of the tetrathiacalix[4]arene is the conformation immobilized to thecone. The template effect of the cesium cation plays an important role in this alkylation reaction. The structuralcharacterization of these products is also discussed.The two-phase solvent extraction data indicated thattetrakis[(2-pyridylmethyl)oxy]thiacalix[4]arenes 4a show strong Ag⁺ affinity and a high Ag⁺ selectivity wasobserved for cone-4a. A good Job plot proves 1:1 coordination of cone-4a with Ag⁺ cation.¹H-NMR titration of cone-4a with AgSO₃CF₃ also clearly demonstrates that a 1:1complex is formed with retention of the original symmetry. In contrast, the 1,2-alternate-4a can form a 2:1 metal/thiacalix[4]arene complex and the two metal-binding sites display positive allostericity. The conformational changes ofpyridine moiety from the original outward orientation of the ring nitrogen to the inside orientation toward thethiacalixarene cavity were observed in the processof Ag⁺ complexation.     

Paramagnetic Properties and Moderately RapidConformational Dynamics in the Cobalt(II) Calix[4]arene Complex by NMR

¹H NMR measurements are reported for the CD₂Cl₂/CDCl₃ solutions of the Co(II) calix[4]arenetetraphosphineoxide complex (I). Temperature dependences of the ¹H NMR spectra of I have been analyzed using the line shape analysis, taking into account the temperature variation of paramagnetic chemical shifts, within the frame of the dynamic NMR method. Conformational dynamics of the 2:1 Co(II) calix[4]arene complexes was conditioned by the pinched cone ↔pinched cone interconversion of I (with activation Gibbs energy ΔG^≠(298K) = 40 ± 3 kJ/mol. Due to substantial temperature dependence of paramagnetic shifts, complex I can be used as model compound for designing an NMR thermosensor reagent for local temperature monitoring.     

Synthesis and NMR spectra of the hydroxyundecahydro-closo-dodecaborate [B12H11OH]2− and its acylated derivatives

Tetrabutylammonium hydroxyundecahydro-closo-dodecaborate was obtained in high yield via [B₁₂H₁₁NMP]^–(NMP =N-methylpyrrolidone) by the modified method. [B_i2H₁₁OH]^2– is easily acylated by aromatic acyl chlorides to give novel compounds [B₁₂H₁₁OCOAr]^2– in high yields. All the compounds were characterized by standard and special NMR methods.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 722–725, March, 1996.     

Ternary metal borides [La,Ce,Pr,Nd,Sm] Os4B4 and [Y,La,Ce,Pr,Nd,Sm,Gd,Tb] Ir4B4 with NdCo4B4-type structure

New ternary metal borides with compositionR. E. T ₄B₄ (R. E.=rare earth metal,T=transition metal) have been synthesized within the systems [La,Ce,Pr,Nd,Sm]–Os–B and [Y, La, Ce, Pr, Nd, Sm, Gd, Tb]–Ir–B. All compounds were found to be crystallizing with NdCo₄B₄-type structure. Magnetic measurements (80–300 K,Curie-Weiss behaviour, _p ~ 16K and µ_eff=9.94µ_B for TbIr₄B₄) indicate Y andR. E. elements (except Ce) to be trivalent in these compounds. The crystal chemistry of the isotypic series [Y,R. E.] [Os,Ir]₄B₄ is discussed.

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Ternäre Metallboride. [La,Ce,Pr,Nd,Sm] Os₄B₄ und [Y,La,Ce,Pr,Nd,Sm,Gd,Tb] Ir₄B₄ mit NdCo₄B₄-Struktur

Zusammenfassung Es wurden neue Metallboride der ZusammensetzungR. E. T ₄B₄ (R. E.=Seltenerdmetall,T=Übergangsmetall) innerhalb der Systeme [La,Ce, Pr,Nd,Sm]–Os–B und [Y,La,Ce,Pr,Nd,Sm,Gd,Tb]–Ir–B hergestellt. Alle Verbindungen kristallisieren entsprechend dem NdCo₄B₄-Typ. Magnetische Messungen (80–300K,Curie-Weiss-Verhalten, _p ~ 16K und µ_eff=9.94µ_B für TbIr₄B₄) zeigen an daß Y und dieR. E.-Elemente (ausgenommen Ce) in diesen Verbindungen trivalent sind. Die Kristallchemie der isotypen [Y,R. E.][Os,Ir]₄B₄-Verbindungen wird diskutiert.

     

Unusual Disordering of Potassium Ions in the Structures of Cluster Rhenium Thiohalides K3[Re6S7Br7] and K4[Re6S8Cl6]

New cluster compounds — rhenium and potassium thiohalides K₃Re₆S₇Br₇ (I) and K₄Re₆S₈Cl₆ (II) — have been synthesized. Their crystal structures have been determined by single crystal X-ray diffraction. The compounds are monoclinic; (I): space group P2₁/c, a = 9.32(1) Å, b = 13.528 Å, c = 12.413 Å, β = 110.21°, Z = 2, R = 0.038; (II): space group C2/m, a = 10.614 Å, b = 17.268 Å, c = 10.448 Å, β = 110.755°, Z = 2, R = 0.042. In both structures, the potassium ions are considerably distorted. The occupancies of the potassium sites are 0.17-0.34 (I) and 0. 01-0.26 (II), correlating well with the coordination numbers (c.n. 7-10 and 2-7 for I and II, respectively). In I, adjacent positions of potassium atoms are aggregated into discrete tetrahedral and angular clusters; in II, the individual (four-and six-membered) cyclic clusters of potassium sites are present along with bent chains of vertex-and edge-sharing tetrahedral “potassium clusters.” The shortest K-K distances in these “clusters” vary from 1.31 Å to 1.54 Å (I) and from 0.66 Å to 1.65 Å (II). The “instability” of the potassium site suggests that I and II are ion conductors.Original Russian Text Copyright © 2004 by S. F. Solodovnikov, S. S. Yarovoi, Yu. V. Mironov, A. V. Virovets, and V. E. Fedorov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 909–917, September–October, 2004.     

Electrodeposition of Lu on W and Al electrodes: Electrochemical formation of Lu–Al alloys and oxoacidity reactions of Lu(III) in the eutectic LiCl–KCl

The electrodeposition of lutetium on inert electrodes and the formation of lutetium–aluminium alloys were investigated in the eutectic LiCl–KCl in the temperature range 673–823 K. On a tungsten electrode, the electroreduction of Lu(III) proceeds in a single step and electrocrystalization plays an important role. Experimental current–time transients are in good agreement with theoretical models based on either instantaneous or progressive nucleation with three dimensional growth of the nuclei, depending on the working temperature. The diffusion coefficient of Lu(III) was determined by chronopotentiometry by applying the Sand equation. The activation energy for diffusion was found to be 31.5 ± 1.3 kJ mol⁻¹. Al₃Lu and mixtures of Al₃Lu and Al₂Lu, characterized by XRD analysis and SEM, were obtained from the LiCl–KCl melt containing Lu(III) by potentiostatic electrolysis using an Al electrode. The activity of Lu and the standard Gibbs energies of formation for Al₃Lu were estimated from open-circuit chronopotentiometric measurements. The E–pO²⁻(potential–oxoacidity) diagram for Lu–O stable compounds in LiCl–KCl at 723 K has been constructed by combining theoretical and experimental data. In this way, the apparent standard potential for the Lu(III)/Lu system has been determined by potentiometry. Potentiometric titrations of Lu(III) solutions with oxide donors, using a yttria stabilized zirconia membrane electrode “YSZME” as a pO²⁻ indicator electrode, have shown the stability of LuOCl and Lu₂O₃ in the melt and their solubility products have been determined at 723 K.     

Choline Esterase Inhibitors and Synthetic Oxalic Acid Receptors Based on Calix[4]arene Derivatives

New reversible butyrylcholine esterase inhibitors based on calix[4]arene derivatives were suggested. A series of new distally disubstituted calix[4]arenes were prepared in 60–80% yields. Some of these compounds showed properties of reversible choline esterase effectors, activating it at low concentrations and inhibiting at high concentrations. The macrocycles prepared were tested in extraction of d,l-tartaric, glycolic, d,l-mandelic, d,l-glutamic, malonic, oxalic, and succinic acids and of sodium acetate. Oxalic acid is efficiently transferred through a liquid impregnated membrane under the action of calix[4]arenes with nitrogen-containing substituents.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 2, 2005, pp. 305–312.Original Russian Text Copyright © 2005 by Stoikov, Khrustalev, Ibragimova, Stoikova, Evtyugin, Antipin, Konovalov.     

New receptors for anions in water: Synthesis, characterization, X-ray structures of new derivatives of 5,11,17,23-tetraamino-25,26,27,28-tetrapropyloxycalix[4]arene

Syntheses and characterization of ten new compounds from the calixarene family, cone - 5,11,17,23- tetrakis(2-pyridylmethylamino)-25,26,27,28-tetrapropyloxycalix[4]arene 4a; cone - 5,11,17,23-tetrakis(3-pyridylmethylamino)-25,26,27,28-tetrapropyloxycalix[4]arene 4b; cone - 5,11,17,23-tetrakis(4-pyridylmethylamino)-25,26,27,28-tetrapropyloxycalix[4]arene 4c; cone - 5,11,17,23-tetrakis(ferrocenylmethylamino)-25,26,27,28-tetrapropyloxycalix[4]arene 4d; cone - 5,11,17,23-tetrakis(2-pyridylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3a; cone - 5,11,17,23-tetrakis(3-pyridylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3b; cone - 5,11,17,23-tetrakis(4-pyridylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3c; cone - 5,11,17,23-tetrakis(ferrocenylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3d; cone - 5,11,17,23-tetrakis(2-thienylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3e and cone - 5,11,17,23-tetrakis(2-pyrrolylmethimino)-25,26,27,28-tetrapropyloxycalix[4]arene 3f are reported. The target compounds 4a-4d were designed to form complexes with anions based on hydrogen bonds and electrostatic interactions in acidic aqueous solutions and the interaction constant 1770 mol⁻¹ dm³ of a 1:1 complex was obtained for the interaction of 4c with sulfate anion in 5 × 10⁻³ M aqueous HCl. The solid state structures of the compounds 3b, 3e and 3f were determined, their stereochemistry and the stereochemistry of the calix[4]arene frame is generally discussed. Raman, infrared and UV-vis spectra of the target compounds and some intermediates are reported, too.     

Synthesis,structure, and complexation properties of tetraamide derivatives of thiacalix[4]arene in different conformations

The interaction of p-tert-butylthiacalix[4]arene with N,N-diethylchloroacetamide was studied in the presence of alkali metal carbonates in acetone. Three stereoisomers, viz., cone, partial cone, and 1,3-alternate, of the tetraamide derivative of thiacalixarene substituted at the lower rim were synthesized selectively using the template effect of alkali metal cations, as well as a complex of the 1,3-alternate stereoisomer with potassium chloride. The structures of the compounds synthesized were studied by 2D NMR spectroscopy. A high extraction ability of the compounds toward alkali metal cations was demonstrated. Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2041–2049, September, 2005.     

New approaches to synthesis of tris[1,2,4]triazolo[1,3,5]triazines

Thermal cyclization of 3-R-5-chloro-1,2,4-triazoles (R = Cl, Ph) afforded 2,6,10-tri-R- tris[1,2,4]triazolo[1,5-a:1′,5′c:1″,5″-e][1,3,5]triazines 5 (R = Ph) and 7 (R = Cl). These compounds are first representatives of this class of heterocycles, whose structures were unambiguously established. Treatment of these compounds with nucleophiles (H₂O/NaOH, NH₃) results in the triazine ring opening to give compounds consisting of three 1,2,4-triazole rings linked in a chain. For example, treatment of cyclic compound 5 with aqueous alkali affords 3-phenyl-1-3-phenyl-1-(3-phenyl-1H-1,2,4-triazol-5-yl)-1,2,4-triazol-5-yl-1H-1,2,4-triazol-5-one. Treatment of 3,7,11-triphenyltris[1,2,4]triazolo[4,3-a:4′,3′c:4″,3″-e][1,3,5]triazine (2) with HCl/SbCl₅ leads to the triazine ring opening giving rise to 5-(3-chloro-5-phenyl-1,2,4-triazol-4-yl)-3-phenyl-4-(5-phenyl-1H-1,2,4-triazol-3-yl)-1,2,4-triazole. Thermal cyclization of the latter produces 3,7,10-triphenyltris[1,2,4]triazolo[1,5-a:4′,3′c:4″,3″-e][1,3,5]triazine (13). Thermolysis of both cyclic compound 2 and cyclic compound 13 is accompanied by the Dimroth rearrangement to yield 3,6,10-triphenyl-tris[1,2,4]triazolo[1,5-a:1′, 5′-c:4″,3″-e][1,3,5]triazine (14). Compounds 13 and 14 are the first representatives of cyclic compounds with this skeleton. ¹³C NMR spectroscopy allows the determination of the isomer type in a series of tris[1,2,4]triazolo[1,3,5]triazines.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 706–712, March, 2005.     

Synthesis of 2-aryl-6,6-dimethyl-8-oxo-5,6,7,8-tetrahydro-1,2,4-4H-triazolo[3,2-b]benzothiazoles and their 3-aryl-[3,4-b] isomers

Summary Condensation of 3-aryl-5-thio-1,2,4-4H-trizoles (2a–i) and 2-bromodimedone (3) inTHF/benzene gave 2-aryl-6,6-dimethyl-8-oxo-5a-hydroxy-5,5a,6,7,8,8a-hexahydro-1,2,4-4H-triazolo[3,2-b]benzothiazoles (5a–i). These were also obtained by a one step synthesis on heating a mixture of dimedone,NBS, and2a–i in benzene containing a trace of benzoyl peroxide. Thermal dehydration of5a–i inPPA/anhydrous ethanol yielded the corresponding 2-aryl-6,6-dimethyl-8-oxo-5,6,7,8-tetrahydro-1,2,4-4H-triazolo[3,2,b]benzothiazoles (6a–i). The formation of [3,4-b] fused isomers (4a–i) during the reaction of2 with3 was ruled out by an unambiguous synthesis of8a–i. Antibacterial screening of selected compounds againstEscherichia coli andStaphylococcus aureus was not encouraging.

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Synthese von 2-Aryl-6,6-dimethyl-8-oxo-5,6,7,8-tetrahydro-1,2,4-4H-triazolo[3,2-b]benzothiazolen und ihrer 3-Aryl-[3,4-b]-Isomeren

Zusammenfassung Die Kondensation von 3-Aryl-5-thio-1,2,4-4H-triazolen (2a–i) mit 2-Bromdimedon (3) inTHF/Benzol ergab 2-Aryl-6,6-dimethyl-8-oxo-5a-hydroxy-5,5a,6,7,8,8a-hexahydro-1,2,4,-4H-triazolo[3,2-b]benzothiazole (5a–i). Dasselbe Ergebnis wurde durch Erhitzen einer Mischung von Dimedon,NBS und2a–i in Benzol unter Zusatz einer Spur Benzoylperoxid in einer einstufigen Synthese erreicht. Thermische Dehydrierung von5a–i inPPA/Ethanol(abs.) ergab die entsprechenden 2-Aryl-6,6-dimethyl-8-oxo-5,6,7,8-tetrahydro-1,2,4-4H-triazolo[3,2-b]benzothiazole (6a–i). Die Bildung [3,4-b]-kondensierter Isomere (4a–i) während der Reaktion von2 mit3 konnte durch eine eindeutige Synthese von8a–i ausgeschlossen werden. Antibakterielles Screening ausgewählter Verbindungen gegenüberEscherichia coli undStaphylococcus aureus brachte keine ermutigenden Resultate.

     

A new synthesis for 1,2,4-triazolo[1,5-a]-pyridines and 1,2,4-triazolo[1,5-a]isoquinolines

Summary Condensation of cyano acid hydrazide1 with cyclopentanone in refluxing ethanolic piperidine yields hydrazone2. With mixtures of aliphatic aldehydes and different active methylene reagents,2 reacts to 1,2,4-triazolo[1,5-a]pyridines (8a–f). Compound2 also reacts with arylidenes9a–g to give triazolopyridines10a–g. Reaction of2 with aromatic aldehydes affords compounds13a–c. Diazotation of2 with aryldiazonium chloride in ethanol at 0 °C leads to the azo adducts15a–d. The thieno-1,2,4-triazolopyridine16 is obtained by reaction of8a with elementary sulfur.16 undergoes cycloaddition with -nitrostyrene, maleic anhydride, N-arylmalemide, and acrylonitrile yielding the isoquinolines21–24. All new compounds have been characterized by their IR,¹H NMR, and mass spectra.

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Ein neuer Syntheseweg für 1,2,4-Triazolo[1,5-a]pyridine und 1,2,4-Triazolo[1,5-a]isochinoline

Zusammenfassung Kondensation des Cyanohydrazids1 mit Cyclopentanon in ethanolischem Piperidin bei Rückflußtemperatur ergibt das Hydrazon2. Mit Gemischen aus aliphatischen Aldehyden und verschiedenen Verbindungen mit aktiven Methylengruppen reagiert2 zu 1,2,4-Triazolo[1,5-a]pyridinen (8a–f). Verbindung2 reagiert außerdem mit den Arylidenen9a–g zu den Triazolopyridinen10a–g. Umsetzung von2 mit aromatischen Aldehyden führt zu den Verbindungen13a–c. Diazotierung von2 mit Aryldiazoniumchloriden in Ethanol bei 0°C ergibt die Azoaddukte15a–d. Das Thieno-1,2,4-triazolylpyridin16 erhält man durch Reaktion von8a mit elementarem Schwefel.16 geht it -Nitrostyrol, Maleinsäureanhydrid, N-Arylmaleimid und Acrylnitril eine Cycloaddition zu den Isochinolinen21–24 ein. Alle neuen Verbindungen wurden durch ihre IR-,¹H-NMR- und Massenspektren charakterisiert.

     

New host molecules based on the thiacalix[4]arene platform for cation recognition

The synthesis of four new tetra-and di-carbonyl p-tert-butyl thiacalix[4]arenes is reported. The three tetracarbonyl compounds differ as conformational isomers (cone, partial cone, and 1,3-alternate). The influence of the alkali metal ion templates on the formation of the different conformational isomers of the compound was studied by the solvent extraction method.     

Stability and DFT Calculated Structure of Protonated Tetraethyl p-tert-Butyltetrathiacalix[4]arenetetraacetate in the cone Conformation

Summary. From extraction experiments in the two-phase water-nitrobenzene system and γ-activity measurements, the stability constant of protonated tetraethyl p-tert-butyltetrathiacalix[4]arenetetraacetate (cone) in nitrobenzene saturated with water was determined. Three different structures of the resulting complex species were indicated by means of the DFT calculations.