Synthese von Thiazolo[3,2−a]thieno[2,3−d]pyrimidin-Derivaten

Derivatives of 5H-thiazolo[3.2?a]thieno[2.3?d]pyrimidine(A), 5H-[1]benzothieno[2.3?d]thiazolo[3.2?a]pyrimidine (B), 4H-thiazolo[3.2?a]thieno[3.2?e]pyrimidine (C) and 5H-[1]benzo-thieno[3.2?e]thiazolo[3.2?a]pyrimidine (D) were synthesized by various methods. Similar reactions are leading to derivatives of thieno[2′.3′∶4.5]pyrimido[2.1?b][1.3]thiazine (E) and [1]benzothieno[2′.3′∶4.5]pyrimido[2.1?b][1.3]thiazine (F).C, D, E, andF are new heterocyclic ring systems. Detailed papers will appear soon.     

Transition metal cyclopentadienyl complexes bearing perfluoro-4-tolyl substituents

Depending on the ratio of starting materials and the reaction conditions, perfluorotoluene (C₆F₅CF₃) reacts with sodium cyclopentadienide (NaCp; Cp = C₅H₅) and excess sodium hydride to afford, after acidic aqueous workup, moderate to high yields of mono-, bis-, tris-, and tetrakis(perfluoro-4-tolyl)cyclopentadiene (1, 2, 3, and 4, respectively). Treatment of 1 with excess NaH in THF afforded sodium (perfluoro-4-tolyl)cyclopentadienide (5) in 90% yield. Reaction of FeBr₂ with 2 equiv. of 5 afforded a 68% yield of (η⁵-C₅H₄C₇F₇)₂Fe (6). Reaction of ZrCl₄(THF)₂ with 2 equiv. of 5 afforded a 58% yield of (η⁵-C₇F₇C₅H₄)₂ZrCl₂ (7). Reaction of Mn(CO)₅Br with 5 afforded a 74% yield of (η⁵-C₇F₇C₅H₄)Mn(CO)₃ (8). Treatment of 3b with NaH and then with Mn(CO)₅Br in DME afforded a 26% yield of [η⁵-1,2,4-(C₇F₇)₃C₅H₂]Mn(CO)₃ (9). Treatment of 3b with NaH and then with FeBr₂ in DME afforded a trace yield of [η⁵-1,2,4-(C₇F₇)₃C₅H₂]₂Fe (10), which was not fully characterized. Dienes 2a, 3a, and 3b and metal complexes 7, 8, and 9 were structurally characterized by single-crystal X-ray diffraction. Infrared spectroscopic analysis of the substituted CpMn(CO)₃ complexes showed a linear increase of 5 cm⁻¹ in the A-symmteric stretching frequency for each C₇F₇ substituent, compared to the analogous value of 4 cm⁻¹ reported earlier for each pentafluorophenyl (C₆F₅) substituent. Solution voltammetric analysis of the substituted ferrocene 6 revealed a shift in the E_1/2 of 465 mV relative to ferrocene, compared to the analogous value of about 340 mV for 1,1′-bis(pentafluorophenyl)ferrocene.     

Computational and cyclic voltammetry studies of high effective-molarity assisted reversible reductions of [4]- and [5]heli-viologens: Potential building blocks for new materials

Computational and cyclic voltammetry studies have been used to explore electrochemical reductions of three helically chiral homologues, 2²⁺, 3²⁺, and 4²⁺, of methyl viologen. Thermochemical-electrochemical cycles are used as frameworks to describe the reversible redox properties of these helically chiral viologens as novel reversible four-sided ECEC (Electron-transfer Chemical-reaction Electron-transfer Chemical-reaction) processes.     

meso-Indanyl calix[4]pyrrole receptors

Two new meso-indanyl-substituted calix[4]pyrrole receptors, 2 and 3, have been synthesized. A range of calix[4]pyrrole host-neutral molecule complexes crystallise from solutions of 2 in a variety of solvents and the structures of four have been elucidated by X-ray crystallography. The F⁻ and Cl⁻ anion affinities of 2 have been measured in acetonitrile, and are significantly different from the corresponding affinities of the prototypical calix[4]pyrrole, the octamethyl-derivative, 1. ESI-FTICR-MS has been used to determine the relative F⁻ and Cl⁻ anion affinities of receptors 1 and 2 in methanol-acetonitrile solution. Deprotonation of 1 and 2 by fluoride is observed (under the conditions of the MS experiment).     

Easy access to 4-nitrothiochroman S,S-dioxides via ring-enlargement from 3-nitrobenzo[b]thiophene

The (E)-2-aryl-1-[2-(methylthio)phenyl]-1-nitroethylenes 5 can easily be oxidized to the relevant sulfones 6 and effectively subjected to cyclization via an intramolecular Michael addition after metallation with lithium bis(trimethylsilyl)amide in THF. After quenching with ammonium chloride the 3-aryl-4-nitrothiochroman S,S-dioxides 2 are obtained as diastereomeric mixtures in good to excellent yields. Both yields and stereochemistry of the ring-closure step appear to be influenced by steric effects of the 3-aryl moiety. As sulfides 5 derive from an initial ring opening of 3-nitrobenzo[b]thiophene (1), the overall 1 to 2 process can be considered as an effective 5 to 6 ring enlargement of the sulfur heterocycle. A conformational ¹H NMR and molecular-mechanics investigation on the isolated diastereomeric 2 has also been accomplished.     

Orbital control of stereochemistry in acid-catalysed addition reactions of endo -tricyclo[3.2.1.02,4]0ct-6-ene

The reaction of endo-tricyclo[3.2.1.0^2,4]oct-6-ene 1 with methanol in the presence of catalytic amounts of toluene-p-sulphonic acid has been shown to give 2-exo- and endo-methoxybicyclo[3.2.1]oct-3-ene (2c) and (2d) and 2-endo-methoxybicyclo[3.2.1]oct-6-ene (13). The formation of 2-exo- methoxybicyclo[3.2.1]oct-3-ene (2c), the major product of reaction, has been probed by deuterium labelling experiments and a series of 6-exo-7-exo- dideuterobicyclo[3.2.1]oct-3-enes synthesised for ²H, ¹H and ¹³C NMR spectral analysis in order unambiguously to determine the stereochemistry of proton attack on endo-tricyclo[3.2.1 0^2,4]oct-6-ene (1). The formation of 2-exo-methoxybicyclo[3.2.1]oct-3-ene (2c) has been determined to involve corner protonation of the cyclopropyl moiety and skeletal rearrangement to an allylic cation with a small but measurable memory effect     

Dual colorimetric sensoring bis(indolyl)calix[4]crown-6

Calix-chromophore, bis(indolyl)calix[4]crown-6 (1) in an oxidized form showing selective colorimetric changes for both alkaline earth cations and F⁻ in CH₃CN, has been newly synthesized. It is observed that the binding ability of 1 for the Ca²⁺ binding enhances in the presence of F⁻. Compound 1 can operate three independent combinational NOR logic gates toward metal cations and anions.     

Synthesis of large chelate rings with diphosphites built on a cyclodextrin scaffold. Unexpected formation of 1,2-phenylene-capped α-cyclodextrins

Two primary face difunctionalised α-cyclodextrins (α-CDs) bearing AC and AD-positioned triarylphosphite ligands have been synthesised and their ability to form large chelate rings has been evaluated. 6^A,6^D-Bis-O-{2-〚(diphenoxyphosphino)oxy〛phenyl}-2^A,2^B,2^C,2^D,2^E,2^F,3^A,3^B,3^C,3^D,3^E,3^F,6^B,6^C,6^E,6^F-hexadeca-O-methyl-α-cyclodextrin (L1) was prepared in three steps in 59% overall yield: (i) treatment of 6^A,6^D-di-O-(methylsulfonyl)-2^A,2^B,2^C,2^D,2^E,2^F,3^A,3^B,3^C,3^D,3^E,3^F,6^B,6^C,6^E,6^F-hexadeca-O-methyl-α-cyclodextrin (1a) with sodium 2-(benzyloxy)phenolate, affording a mixture of the corresponding bisaryloxy substitution product 2a; (ii) cleavage of the benzyl groups of 2a with formation of bisphenol 6a; (iii) reaction of 2a with chlorodiphenylphosphite to afford L1. Diphosphite L2 was obtained in a similar manner using the AC dimesylate 1b (yield: 54%). In step (i) of each synthesis, the unexpected formation of a catecholato-capped CD was observed as a result of benzyl loss under the used arylation conditions. The AD-bridged product was characterised by a single crystal X-ray diffraction study. In the solid state, the CD torus adopts the usual circular shape while four glucose rings, although not distorted, are considerably tilted towards the cavity axis. Both ligands, L1 and L2, when reacted with the cationic complexes AgBF₄ or 〚Rh(norbornadiene)(THF)₂〛X (X = BF₄, PF₆), produced selectively chelate complexes having up to 29-membered metallomacrocycles in high yields. Rhodium systems based on either L1 or L2 catalyse effectively the hyfroformylation of 1-octene (TOF up to 1200 mol mol^–1 of Rh h^–1). Hydrogenation of dimethyl itaconate with a Rh(I)/L2 complex produced dimethyl (R)-(+)-methylsuccinate with an EE as high as 83.6%.     

Electronic structure and reactivity of propellanes : The stereochemistry of diels-alder- and related cyclo-additions in the series of [4.4.2] and [4.4.3] propellanes; models and interpretations

The stereochemistry of the products obtained by Diels-Alder addition of 1 to 2-6 and 14 and 15 has been rationalised. In case of the propellanes 2-6 a frontier MO approach substantiated by extended Hückel calculations has been invoked. For 14 and 15 the Coulomb interaction between the polar SO and SO₂ groups and the dienophile is decisive for the observed stereochemistry.     

A practical route for synthesizing a PET ligand containing [F]fluorobenzene using reaction of diphenyliodonium salt with [F]F

The aim of this study was to develop a practical route for preparing a fluorine-18 ([¹⁸F]) labelled ligand ([¹⁸F]1) containing [¹⁸F]fluorobenzene ring by employing the reaction of diphenyliodonium salt with [¹⁸F]F⁻. Diphenyliodonium tosylate (2) was synthesized from tributylphenylstannyl compound (6) with [hydroxy(tosyloxy)iodo]benzene (7). Using this method, [¹⁸F]DAA1106 ([¹⁸F]3a), a positron emission tomography ligand for imaging peripheral-type benzodiazepine receptor, was prepared.     

Concise and efficient synthesis of E-stereoisomers of exo-cyclic carbohydrate enones. Aldol condensation of dihydrolevoglucosenone with five-membered aromatic aldehydes Part 1

Stereoselective synthesis of exocyclic enones 10–17 via a base-catalyzed direct aldol condensation between dihydrolevoglucosenone 1 and heterocyclic aldehydes 2–9 is described. The reaction is performed under mild conditions and is applicable to variety of heterocyclic aldehydes. E-Steroisomers of exo-cyclic enones are the only products. They are very easy to isolate and were formed in good to excellent (72–88%) yield. ¹H NMR, ¹³C NMR analyses provide the structural assignment and absolute stereochemistry of the condensation products. Single-crystal X-ray diffraction of condensation product 12, additionally supports the structural assignment.     

Organosilicon chalcogenides with trisilane units - bicyclo[3.3.1]nonanes, bicyclo[3.2.2]nonanes and spiro[4.4]nonanes

Treatment of 1,2,3-trichloropentamethyltrisilane (1) with H₂S/NEt₃ results in the formation of a mixture of two isomers of (Me₅Si₃)₂S₃ with a bicyclo[3.3.1]nonane (2a) and a bicyclo[3.2.2]nonane (2b) skeleton, while the reaction of 1 with Li₂Se yields one product only, (Me₅Si₃)₂Se₃ (3a), with a bicyclo[3.3.1]nonane structure. Besides ¹H, ¹³C, ²⁹Si and ⁷⁷Se NMR spectroscopy 3a has also been characterized by a crystal structure analysis.Compounds Si(SiMe₂EMR₂E)₂ (5a-h: MR₂: SiMe₂ (5a, c, d), SiPh₂ (5b), GeMe₂ (5e, f), SnMe₂ (5g, h); E=S (5a, b, e, g), Se (5c, f, h), Te (5d)) with a spiro[4.4]nonane skeleton have been obtained in mixture with varying amounts of the corresponding six-membered rings (R₂ME)₃ by reactions of mixtures of 1,2,2,3-tetrachlorotetramethyltrisilane (4) and diorganodichlorosilanes, Me₂GeCl₂ or Me₂SnCl₂, with H₂S/NEt₃, Li₂Se or Li₂Te and have been characterized in situ by multinuclear NMR spectroscopy (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn, ⁷⁷Se, ¹²⁵Te) and GC-MS.     

Chiral aminocyclopentene-based cycloaddition strategies to bicyclic [3.3.0] rings

Two cycloaddition methods were applied to chiral protected aminocyclopentenes 2 and 9 and provided novel bicyclic products 3 and 4 in good yields. The explanation for the observed stereochemistry was based on the sterically encumbered β-face forcing the cycloadditions to occur on the α-face of the cyclopentene ring. The stereochemistry of 4 was confirmed by X-ray of the fumarate salt 10 and showed the trans-relationship between the newly formed ring and the chiral –NHBoc group.     

Synthese von Tricarbonyl-η5-cyclohexadienyl-wolframat und Tricarbonyl-η5-cyclohexadienyl-methyl-wolfram

η⁶-Arene-tricarbonyl-tungsten (arene = benzene (1a), toluene (1b), m-xylene (1C), P-xylene (1D), o-xylene (1E), mesitylene (1F)) yield with potassium-tri-sec-butylboranate correspondingly methyl-substituted tricarbonyl-η⁵-cyclohexadienyl-tungstates (2A–2F). Similarly 1A reacts with methyllithium to tricarbonyl-η⁵-anti-6-methylcyclohexadienyl-tungstate (4A). In THF 2A–2F and 4A are converted by methyliodide to tricarbonyl-μ⁵-cyclohexadienyl-tungsten (3A–3F) and tricarbonyl-η⁵-anti-6-methylcyclophexadienyl-methyl-tungsten (5A). The complexes were characterized by C, H elemental analyses and by IR and ¹H-NMR spectroscopy.     

Synthesis and characterization of a new pillar[5]arene-based [1]rotaxane

In this study, we reported the synthesis of three kinds of mono-functional pillar[5]arene derivatives PRI, PRII and R and their structures were studied by 1D and 2D NMR spectra and mass spectra. The 2D NMR spectra including ¹H-¹³C HSQC, ¹H-¹H COSY and NOESY spectra indicated that PRI and PRII are both stable self-included pseudo[1]rotaxanes in CDCl₃. These original structures are promising compounds for the design of pillar[5]-based [1]rotaxane. And the results showed that R could exist stable in CDCl₃ and DMSO because of the coordination of N-H?O hydrogen bonding interaction and C-H?π interaction.     

Preparations and properties of pseudo-geminal ketones of tris-[2.2.2]- and tetrakis[2.2.2.2]parazylylene

Pseudo-geminal bridged ketones of tris[2.2.2]paraxylylene, 1, and of tetrakis[2.2.2.2]paraxylylene, 2, were prepared and their spectral properties were investigated in comparison with those of dibenzosuberone, 3. The CO stretching band of 1 was observed at abnormally high frequency region (by ca. 50 cm^?1) compared with that of 3, while that of 2 was at a position similar to that of 3. The electronic spectrum of 1 showed that 1 has enormous loss of conjugation due to lack of coplanarity between CO and aromatics. The chemical shift of H⁰, ortho to CO, of 1 also supported this structural characteristic.     

[1,1-Bis(diphenylphosphino)ferrocene]palladium(II) complexes with fluorinated benzenethiolate ligands: examination of the electronic effects in the solid state, solution and in the Pd-catalyzed Heck reaction with the catalytic system [Pd(dppf)(SRF)2]

A series of palladium thiolate complexes of the type [Pd(dppf)(SR_F)₂] have been synthesized in good yields by metathetical reactions of [Pd(dppf)Cl₂] with [Pb(SR_F)₂], (SR_F=⁻SC₆F₅, ⁻SC₆F₄-4-H, ⁻SC₆H₄-2-CF₃, ⁻SC₆H₄-4-F, ⁻SC₆H₄-3-F) and their crystal structures determined. The effect of the different thiolates in the structural properties of the complexes both in the solid state and in solution have been analyzed. Heck coupling reactions were carried out using the complexes [Pd(dppf)(SR_F)₂], SR_F=⁻SC₆F₅ (1), ⁻SC₆F₄-4-H (2), ⁻SC₆H₄-2-CF₃ (3), ⁻SC₆H₄-4-F (4), ⁻SC₆H₄-3-F (5) as catalysts in order to examine both the effect of the thiolates and the P-Pd-P bite angles in the reaction of bromobenzene and styrene. The results obtained indicate that electron-withdrawing substituents may favor higher yields in the Pd catalyzed Heck reaction using [Pd(dppf)(SR_F)₂] as catalysts.     

Synthesis and cation complexation of calix[4]azacrowns and a spirobiscalix[4]azacrown

The synthesis and complexation properties of three new derivatives, one spirobiscalix[4]azacrown (1) and two calix[4]azacrown (2 and 3), are reported. Complexation studies of the three ligands toward transition and heavy metal cations have been carried out and monitored by UV absorption spectrophotometry in acetonitrile. Mononuclear complexes were detected for all complexes, whereas binuclear species (M₂L) were also formed in the case of ligand 1 with Cu²⁺ and Pb²⁺. The extraction properties of 1, 2 and 3 toward Cu²⁺, Zn²⁺, Pb²⁺, Ag²⁺ and Cd²⁺ are also reported. The results showed that complexation is the main factor affecting extraction with ligands 2 and 3, while with ligand 1 it is not.     

Pyrrolamidocalix[4]arenes: new receptors for anion recognition

Pyrrolamidocalix[4]arenes 1-4, members of a new class of anion receptors bearing pyrrolic units at the upper rim of calix[4]arene macrocycle, have been readily synthesized in good yields. Derivatives 1 and 3, with unsubstituted pyrrole units, show a good selectivity for over F⁻ and AcO⁻, while the presence of electron-withdrawing NO₂ substituents in 2 and 4 inverts the selectivity favoring more basic AcO⁻ and F⁻. In addition, it is demonstrated that the flexibility of calix[4]arene skeleton, present in 1 but absent in 3, is very important in the fitting process that leads the amidopyrrole moieties to wrap the tetrahedral guest.     

[Cd(Sn9)2]6− and [Cd(Ni@Sn9)2]6−: Reactivity and coordination chemistry of empty and Ni-centered [Sn9]4− Zintl ions

To investigate the reactivity of homoatomic clusters [E₉]^4? (E = Si-Pb) and intermetalloid clusters [M@E₉]^q?, the reactions of the Zintl anions [Sn₉]^4? and [Ni@Sn₉]^4? with the CdMes₂ (Mes = Mesitylene) in the presence of 2.2.2-crypt were carried out. Two new compounds [K(2.2.2-crypt)]₆[(Sn₉)Cd(Sn₉)]·en (1) and [K(2.2.2-crypt)]₆[(Ni@Sn₉)Cd(Ni@Sn₉)]·en (2) were afforded. Both 1 and 2 were characterized by single-crystal X-ray diffraction, energy dispersive X-ray (EDX), and electrospray ionization mass spectrometry (ESI-MS), and can be viewed as two [Sn₉]^4? or [Ni@Sn₉]^4? subunits bridged by Cd ion in an η³:η³ coordination mode. Quantum chemical calculations reveal the relationships between the geometries and electronic structures of clusters 2a, [Ni₃Ge₁₈]^4? and [Cu₄@Sn₁₈]^4?. Further electron localization technique (AdNDP method) was performed to explain chemical bonding patterns of 1a.