Synthesis and complexing properties of double armed diaza‐15‐crown‐5 and diaza‐18‐crown‐6 ethers having 4′‐hydroxy‐3′,5′‐disubstituted benzyl groups

A series of double armed diaza‐15‐crown‐5 ethers (9a ‐ 16a) and diaza‐18‐crown‐6 ethers (9b ‐ 16b) have been prepared by the Mannich reaction of 2,6‐disubstituted phenols with the corresponding N,N'‐dimethoxymethyldiaza‐crown ethers in benzene. The crystal structures of the diaza‐18‐crown‐6 ethers having iso‐propyl (10b) , tert‐butyl (11b) , and mixed methyl and tert‐butyl groups (12b) at positions 3′ and 5′ of the phenolic side arms were determined using X‐ray diffraction methods. Competitive transport by these ligands for sodium, potassium and cesium cations were measured under basic‐source phase and acidic‐receiving phase conditions.     

Synthesis of lipophilic lariat ethers with pendant N‐(X)sulfonyl carboxamide groups

Synthetic routes to sixteen lipophilic lariat ether N‐(X)sulfonyl carboxamides with X = trifluoromethyl, methyl, phenyl, and p‐nitrophenyl are described. For this new family of proton‐ionizable lariat ethers in which the acidity can be ‘tuned’ by X group variation, the ring size is systematically varied from 12‐crown‐4 to 14‐crown‐4 to 15‐crown‐5 to 18‐crown‐6.     

Preparation of N‐(4′,6′‐difluoro‐2′‐hydroxybenzyl)‐monoaza‐15‐crown‐5 and x‐ray crystal structure of potassium thiocyanate complex: A molecular partition wall

Armed monoaza‐15‐crown‐5 having a 4′,6′‐difluoro‐2′‐hydroxybenzyl group as an additional binding site ( 2 ) has been prepared by the Mannich reaction of N‐methoxymethylmonoaza‐15‐crown‐5 with 3,5‐difluorophenol. The reactive site on 3,5‐difluorophenol for the Mannich reaction was predicted by an electrostatic potential calculation (density functional calculation, SVWN/DN* method). Ligand 2 is interesting, because it has two possible binding sites (phenolic OH group and fluorine atom) in the side arm. An X‐ray crystal structure of the potassium thiocyanate complex of ligand 2 revealed that the oxygen atom of the phenolic OH group binds to the potassium cation incorporated in the crown ether ring, and two water molecules are enclosed by two armed crown ethers with the crown ethers forming partition walls.     

Ferrocenyl,Alkyl, and Aryl‐Pyrido[2,3‐d]Pyrimidines as Vasorelaxant of Smooth Muscle of Rat Aorta via cAMP Conservation Through Phosphodiesterase Inhibition

New pyrido[2,3‐d]pyrimidines 11 , 12 , 13 , and 21 have been synthesized. The vasorelaxant effect on smooth muscle isolated from rat aorta, via PDEs inhibition, of these compounds along with other pyrido[2,3‐d]pyrimidines 14 , 15 , 16 , 17 , 18 , 19 , 20 reported earlier by our group, has also been determined. These pyrido[2,3‐d]pyrimidines 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 were synthesized by the reaction of ferrocenyl‐ethynyl ketones ( 1 , 2 , 3 , 4 ) or α‐alkynyl ketones ( 5 , 6 , 7 , 8 , 9 , 10 ) with 6‐amino‐1,3‐dimethyluracil using [Ni(CN)₄]^?4 as an active catalytic species, formed in situ in a Ni(CN)₂/NaOH/H₂O/CO/KCN aqueous system. Evaluation of the vasorelaxant effect of compounds 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 demonstrated that all compounds relax the tissue in a concentration‐dependent manner. The structural changes do not alter the effectiveness; however, there are differences related to potency expressed as EC₅₀. Compounds 12 (7‐ferrocenyl‐1,3‐dimethyl‐5‐(m‐tolyl)‐pyrido[2,3‐d]pyrimidine) and 13 (7‐ferrocenyl‐1,3‐dipropyl‐5‐(4‐metoxyphenyl)‐pyrido[2,3‐d]pyrimidine) were the most potent compounds, even more than rolipram, reference drug; the EC₅₀ was 0.41 ± 0.02 μM and 0.81 ± 0.11 μM for 12 and 13 , correspondingly. The EC₅₀ of compounds 15 (7‐ferrocenyl‐1,3‐dimethyl‐5‐phenyl‐pyrido[2,3‐d]pyrimidine), 14 (7‐ferrocenyl‐5‐(3,5‐dimethoxyphenyl)‐1,3‐dimethylpyrido[2,3‐d]pyrimidine), and 19 (5‐n‐butyl‐7‐ethyl‐1,3‐dimethylpyrido[2,3‐d]pyrimidine) was similar to EC₅₀ of rolipram. Compounds 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 significantly induce concentration‐dependent vasorelaxation in endothelium‐intact aortic rings. In addition, the relaxation responses to each compound in either endothelium‐intact or endothelium denuded aortic rings were comparable, suggesting that removal of the functional endothelium has no significant influence on its intrinsic vasorelaxant activity. In vitro capability of conserving cyclic‐AMP or cyclic‐GMP (adenosine and guanosine 3′, 5′‐cyclic monophosphate) via PDE inhibition for compounds 12 , 13 , 14 , 15 and 19 was evaluated. Compounds 15 and 19 show the highest percent inhibition effect (94.83% and 83.98%, respectively) for the decomposition of c‐AMP. Docking studies showed that the compound 15 was selective for the inhibition of PDE‐4.     

The synthesis of novel crown ethers,part X, 4‐propyl‐and 3‐ethyl‐4‐methylchromenone‐crown ethers

Starting from ethyl propionylacetate, and ethyl 2‐ethylacetoacetate we prepared 4‐propyl‐7,8‐, 4‐propyl‐6,7‐, 3‐ethyl‐4‐methyl‐7,8‐ and 3‐ethyl‐4‐methyl‐6,7‐dihydroxy‐2H‐chromenones which were allowed to react with the bis‐dihalides or ditosylates of glycols in DMF/Na₂CO₃ to afford the 6,7‐ and 7,8‐chromenone derivatives of 12‐crown‐4, 15‐crown‐4 and 18‐crown‐6. The products were identified using ir, ¹³C and ¹H nmr, ms and high resolution mass spectroscopy. The cation selectivities of chromenone crown ethers with Li⁺, Na⁺ and K⁺ cations were estimated from the steady state emission fluorescence spectra of free and cation complexed chromenone macrocyclic ethers in acetonitrile.     

Kinetic Study of the Oxidation of Catechols in the Presence of Some Aza‐crown Ethers by Digital Simulation of Cyclic Voltammograms

The electrochemical oxidation of catechols ( 1 ) have been studied in the presence of diaza‐18‐crown‐6 (DA18C6) ( 3a ), diaza‐15‐crown‐5 (DA15C5) ( 3b ), and aza‐15‐crown‐5 (A15C5) ( 3c ) as nucleophiles in aqueous solution, by means of cyclic voltammetry and controlled‐potential coulometry. The results indicate the participation of electrochemically generated o‐benzoquinones ( 2 ) in Michael‐type reaction with aza‐crown ethers ( 3 ) to form the corresponding new o‐benzoquinone‐aza‐crown ether adducts ( 5 ). Based on ECE mechanism, the observed homogeneous rate constants (k_obs) of the reaction of o‐bezoquinones ( 2 ) with aza‐crown ethers ( 3 ) were estimated by comparing the experimental cyclic voltammograms with the digital simulated results. The calculated observed homogeneous rate constants (k_obs) was found to vary in the order DA18C6>DA15C5>A15C5.     

Luminescence properties of soluble 2,2′,7,7′‐Tetrakis(2‐(9‐hexyl‐9H‐carbazol‐3‐yl)‐vinyl)‐9,9′‐spirobifluorene‐labeled dendrimers: Photoluminescence and electroluminescence

New light emitting dendrimers were synthesized by reacting 3,5‐bis‐(3,5‐bis‐benzyloxy‐benzyloxy)‐benzoic acid or 3,5‐bis‐[3,5‐bis‐(3,5‐bis‐benzyloxy‐benzyloxy)‐benzyloxy]‐benzoic acid with a carbazolyl vinyl spirobifluorene moiety. A blue‐emitting core dye was encapsulated by multibenzyloxy dendrons, and two dendrimers having different densities of dendrons were prepared. Photoluminescence (PL) studies of the dendrimers demonstrated that at the higher density of benzyloxy dendrons, the featureless vibronic transitions were improved, causing lesser excimer emission. The similarity of the solution and solid emission spectra of the larger dendrimer, 10 , revealed the suppression of molecular aggregation in the solid film, which is attributed to the presence of the bulky benzyloxy dendrons. The electroluminescence spectra of multilayered devices made using 10 predominantly exhibited blue emissions; similar emission was observed in the PL spectra of its thin film. The multilayered devices made using 3 , 9 , and 10 showed luminances of 1021 cd m^?2 at 5 V, 916 cd m^?2 at 6 V, and 851 cd m^?2 at 6.5 V, respectively. The largest dendrimer, 10 , bearing a greater number of benzyloxy dendrons, exhibited a blue‐like emission with CIE 1931 chromaticity coordinates of x = 0.16 and y = 0.13, which is due to the influence of a higher shielding effect. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 501–514, 2008     

DFT Study for a Series of Less-Symmetrical Crown Ethers and Their Complexes with Alkali Metal Cations

A series of ring‐contracted (14‐crown‐5, 17‐crown‐6) and ring‐enlarged (16‐crown‐5, 17‐crown‐5, 19‐crown‐6, 20‐crown‐6) crown ethers and their complexes with alkali‐metal cations Na⁺ and K⁺ had been explored using density functional theory (DFT) at B3LYP/6‐31G* level in order to reveal the effects of the methylene‐chain length in a crown ether. The nucleophilicity of all crown ethers had been investigated by the Fukui functions. The quantum chemistry parameters, such as the energy gap (ΔE), the highest occupied molecular orbital energy (E_HOMO) and the lowest unoccupied molecular orbital energy (E_LUMO) for less‐symmetrical crown ethers and symmetrical frameworks (15‐crown‐5, 18‐crown‐6) had been calculated. In addition, the thermodynamic energies of complexation reactions had also been studied. The results of the DFT calculations show that the methylene‐chain length plays an important role in determining the structure characters of the crown ethers and also strongly influences the properties of the ethers. Some of the calculated results are in a good agreement with the experimental values.     

Synthesis of 4‐alkyl‐1,2‐diphenyl‐3,5‐dioxopyrazolidines possessing aryl methylsulfonyl and sulfonamide pharmacophores for evaluation as selective cyclooxygenase‐2 (COX‐2) inhibitors

A group of 1,2‐diphenyl‐3,5‐dioxopyrazolidines possessing a methylsulfonyl ( 11 ) or sulfonamide ( 15 ) substituent at the para position of the N¹‐phenyl ring, in conjunction with a hydrogen, methyl or fluoro sub‐stituent at the para position of the N²‐phenyl ring, and a C‐4 n‐butyl, methyl or spiro‐cyclopropyl substituent were synthesized for evaluation as potential cyclooxygenase‐2 (COX‐2) selective inhibitor antiinflammatory agents. The title compounds 11 and 15 were synthesized using a four‐step and a three‐step reaction sequence, respectively. Thus, the acetic acid promoted condensation of a nitrosobenzene 5 with an aniline derivative ( 6, 12 ) gave the corresponding azobenzene product ( 8, 13 ) which was reduced with zinc dust in the presence of ammonium chloride to yield the corresponding hydrazobenzene ( 9, 14 ). Base‐catalyzed condensation of 9 and 14 with a malonyl dichloride ( 10 ) afforded the target 3,5‐dioxopyrazolidine product ( 11,15 ). 4‐n‐Butyl‐1‐(4‐methylsulfonylphenyl)‐2‐phenyl‐3,5‐dioxopyrazolidine ( 11a ) was a selective COX‐1 inhibitor (COX‐1 IC₅₀ = 8.48 μM). In contrast, 4‐n‐butyl‐1‐(4‐methylsulfonylphenyl)‐2‐(4‐tolyl)‐3,5‐dioxopyrazolidine ( 11b , COX‐2 IC₅₀ = 11.45 μM) and 4‐n‐butyl‐1‐(4‐methylsulfonylphenyl)‐2‐(4‐fluorophenyl)‐3,5‐dioxopyrazoli‐dine ( 11c , COX‐2 IC₅₀ = 9.86 μM) were about 46‐fold and 20‐fold less selective COX‐2 inhibitors respectively, relative to the reference drug celecoxib.     

A New Synthesis of Ciliapterin and Dictyopterin. Ene Reactions of (Alkenylamino)‐nitroso‐pyrimidines

A comparison of the reactivity of (acylamino)‐nitroso‐pyrimidines 1 and the alkenylamino analogue 17 in intramolecular ene reactions showed the considerably lower reactivity of 17 , leading to the pteridine 18 . Pteridin‐7‐one 11 resulting from 1 (R¹=OBn, R²=Me) was transformed into 4‐(benzyloxy)‐6‐[(E)‐prop‐1‐enyl]pteridin‐2‐amine ( 13 ) by O‐triflation, followed by reduction with LiBHEt₃, while the 4‐MeO analogue 18 was prepared by spontaneous oxidation of the initial ene product of 17 . The (alkenylamino)‐nitroso‐pyrimidine 17 was synthesized by substitution of the dimethoxy‐nitroso‐pyrimidine 16 with the allylamine 15 . Ciliapterin ( 5 ) and dictyopterin ( 7 ) were synthesized from pteridine 18 by a Sharpless asymmetric dihydroxylation.     

Supramolecular Fullerene Chemistry: A Comprehensive Study of Cyclophane‐Type Mono‐ and Bis‐Crown Ether Conjugates of C70

The covalently templated bis‐functionalization of C₇₀, employing bis‐malonate 5 tethered by an anti‐disubstituted dibenzo[18]crown‐6 (DB18C6) ether, proceeds with complete regiospecificity and provides two diastereoisomeric pairs of enantiomeric C₇₀ crown ether conjugates, (±)‐ 7a and (±)‐ 7b , featuring a five o'clock bis‐addition pattern that is disfavored in sequential transformations (Scheme 1). The identity of (±)‐ 7a was revealed by X‐ray crystal‐structure analysis (Fig. 6). With bis‐malonate 6 containing a syn‐disubstituted DB18C6 tether, the regioselectivity of the macrocylization via double Bingel cyclopropanation changed completely, affording two constitutionally isomeric C₇₀ crown ether conjugates in a ca. 1 : 1 ratio featuring the twelve ( 16 ) and two o'clock ((±)‐ 15 ) addition patterns, respectively (Scheme 3). The X‐ray crystal‐structure analysis of the twelve o'clock bis‐adduct 16 revealed that a H₂O molecule was included in the crown ether cavity (Figs. 7 and 8). Two sequential Bingel macrocyclizations, first with anti‐DB18C6‐tethered ( 5 ) and subsequently with syn‐DB18C6‐tethered ( 6 ) bis‐malonates, provided access to the first fullerene bis‐crown ether conjugates. The two diastereoisomeric pairs of enantiomers (±)‐ 28a and (±)‐ 28b were formed in high yield and with complete regioselectivity (Scheme 9). The cation‐binding properties of all C₇₀ crown‐ether conjugates were determined with the help of ion‐selective electrodes (ISEs). Mono‐crown ether conjugates form stable 1 : 1 complexes with alkali‐metal ions, whereas the tetrakis‐adducts of C₇₀, featuring two covalently attached crown ethers, form stable 1 : 1 and 1 : 2 host‐guest complexes (Table 2). Comparative studies showed that the conformation of the DB18C6 ionophore imposed by the macrocyclic bridging to the fullerene is not particularly favorable for strong association. Reference compound (±)‐ 22 (Scheme 4), in which the DB18C6 moiety is attached to the C₇₀ sphere by a single bridge only and, therefore, possesses higher conformational flexibility, binds K⁺ and Na⁺ ions better by factors of 2 and 20, respectively. Electrochemical studies demonstrate that cation complexation at the crown ether site causes significant anodic shifts of the first reduction potential of the appended fullerene (Table 3). In case of the C₇₀ mono‐crown ether conjugates featuring a five o'clock functionalization pattern, addition of 1 equiv. of KPF₆ caused an anodic shift of the first reduction wave in the cyclic voltammogram (CV) by 70 to 80 mV, which is the result of the electrostatic effect of the K⁺ ion bound closely to the fullerene core (Fig. 14). Addition of 2 equiv. of K⁺ ions to C₇₀ bis‐crown ether conjugates resulted in the observation of only one redox couple, whose potential is anodically shifted by 170 mV with respect to the corresponding wave in the absence of the salt (Fig. 16). The synthesis and characterization of novel tris‐ and tetrakis‐adducts of C₇₀ are reported (Schemes 5 and 6). Attempts to prepare even more highly functionalized derivatives resulted in the formation of novel pentakis‐ and hexakis‐adducts and a single heptakis‐adduct (Scheme 7), which were characterized by ¹H‐ and ¹³C‐NMR spectroscopy (Fig. 10), as well as matrix‐assisted laser‐desorption‐ionization mass spectrometry (MALDI‐TOF‐MS). Based on predictions from density‐functional‐theory (DFT) calculations (Figs. 12 and 13), structures are proposed for the tris‐, tetrakis‐, and pentakis‐adducts.     

Diphosphapodanden, [12]‐, [15]‐ und [18]Diphosphacoronanden,Diphosphacryptand‐8 und Alkalimetall‐Komplexe

Diphosphapodands, [12]‐, [15]‐, and [18]Diphosphacoronands, Diphosphacryptand‐8, and Alkali‐Metal Complexes The cyclizing bis‐phosphonium‐salt formation of the open‐chain bis‐phosphine 17a (1,1,7,7‐tetrabenzyl〈P.O.P‐podand‐7〉) with diethylene glycol derived dibromide 13a yields the 12‐membered cyclic bis‐phosphonium salt 20 (4,4,10,10‐tetrabenzyl‐12〈O.P.O.P‐coronand‐4〉‐4,10‐diium dibromide) in yields as high as 50–60%. The 1,1,10,10‐tetrabenzyl〈P.O₂.P‐podand‐10〉 17b forms with 13a the 15‐membered cyclic bis‐phosphonium salt 21 (7,7,13,13‐tetrabenzyl‐15〈O₂.P.O.P‐coronand‐5〉‐7,13‐diium dibromide) with the same high yield. By quaternization of the bis‐phosphine 17b with triethylene glycol derived dibromide 13b , the 18‐membered 7,7,16,16‐tetrabenzyl‐18〈O₂.P.O₂.P‐coronand‐6〉‐7,16‐diium dibromide 24 is obtained in 50% yield, too. The Wittig reaction of the cyclic phosphonium salts with benzaldehyde yields the 12‐, 15‐, and 18‐membered cyclic bis‐benzylphosphine dioxides 9, 10 , and 11 as cis‐ and trans‐isomers beside trans‐stilbene. The 7,13‐dioxido‐7,13‐dibenzyl‐15〈O₂.P.O₂.P‐coronand‐5〉 10 forms a crystalline 1 : 1 Na‐complex 23 , which exists as a dimer. The structure of 23 was established by an X‐ray analysis and spectroscopic data. The 7,16‐dibenzyl‐18〈O₂.P.O₂.P‐coronand‐6〉 28 that is available by reduction of 11 with CeCl₃/LiAlH₄ reacts with triethylene glycol derived dibromide 13b under Ruggly Ziegler‐dilution conditions to give the bicyclic bis‐phosphonium salt 29 (1,10‐dibenzyl〈P[O₂]₃.P‐cryptand‐8〉‐1,10‐diium dibromide) in 18% yield. Again, by the Wittig procedure with benzaldehyde, the 7,16‐dioxido〈P[O₂]₃P‐cryptand‐8〉 12 is obtained as the first diphosphacryptand. The FD‐MS (CH₂Cl₂) of the cyclic bis‐phosphine dioxides 10 – 12 show that they exist as [2M+Na]⁺ complexes. The complex formation constants K_a of 9 – 11 with alkali‐metal cations are studied and compared with the complex formation of corresponding crown ethers.     

Synthesis of Ethylene‐bridged Heterocyclic Bidentate P(III)N‐Ligands — Oxidation and Complexation Studies

A series of phosphor(III)inanone ligands 4‐7 , linked by ethylene bridges between the nitrogen atoms of the heterocyclic rings, were synthesized by the reaction of the bis‐PCl derivative 3 with the appropriate trimethylsilylamines. The bis‐phosphor(V)inanone compounds 8‐11 were obtained by the oxidation of 4‐7 with hexafluoroacetone (HFA). Oxidation of 4 and 6 with tetrachloro‐orthobenzoquinone (TOB) gave the bis‐phosphor(V)inanones 12 and 13 . The reaction of 4‐6 with [Pt(COD)Cl₂] led to the platinum complexes 14‐16 . All the σ³‐phosphorinanone compounds 4‐7 and the σ⁵‐phosphorinanone compounds 8‐10 , 12 and 13 exist as a mixture of two conformers, as indicated by two signals in the ³¹P‐NMR spectra. However, compounds 9 and 11 exist as single conformers, both display only one sharp singlet in the ³¹P‐NMR spectra. The Pt‐complexes 15 and 16 contain two conformers; one conformer of 16 could be isolated by crystallization. X‐ray crystal structure determinations for compounds 8 , 14 and 16 were conducted, revealing inversion symmetry for 8 and cis arrangement for 14 and 16 .     

A Facile and Efficient Synthesis of 2‐(5‐(4‐Substitutedphenyl)‐4, 5‐dihydro‐3‐phenylpyrazol‐1‐yl)‐6‐Substitutedbenzothiazoles and Their Biological Studies

A series of new 1‐substituted 3, 5‐diarylpyrazolines ( 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ) were synthesized in good yield by both conventional and microwave‐assisted synthesis from α, β‐ unsaturated ketones ( 6 , 7 , 8 , 9 ) in n‐butanol and benzothiazole hydrazines ( 2 , 3 , 4 , 5 ). All the new compounds were characterized by IR, NMR, and mass spectral data. The synthesized compounds ( 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ) were evaluated for antibacterial and anthelmintic activities. The compounds showed potent anthelmintic activity against earthworm species (Eudrilus eugeniae) and moderate antibacterial activity against bacterial strains such as Gram positive bacteria, Enterococcus faecalis, Staphylococcus aureus, and Bacillus subtilis, and Gram negative bacteria, Escherichia coli and Proteus mirabilis.     

Oxidative Fragmentations of the 5α‐ and 5β‐Hydroxy‐B‐norcholestan‐ 3β‐yl Acetates

Oxidations of 5α‐hydroxy‐B‐norcholestan‐3β‐yl acetate ( 8 ) with Pb(OAc)₄ under thermal or photolytic conditions or in the presence of iodine afforded only complex mixtures of compounds. However, the HgO/I₂ version of the hypoiodite reaction gave as the primary products the stereoisomeric (Z)‐ and (E)‐1(10)‐unsaturated 5,10‐seco B‐nor‐derivatives 10 and 11 , and the stereoisomeric (5R,10R)‐ and (5S,10S)‐acetals 14 and 15 (Scheme 4). Further reaction of these compounds under conditions of their formation afforded, in addition, the A‐nor 1,5‐cyclization products 13 and 16 (from 10 ) and 12 (from 11 ) (see also Scheme 6) and the 6‐iodo‐5,6‐secolactones 17 and 19 (from 14 and 15 , resp.) and 4‐iodo‐4,5‐secolactone 18 (from 15 ) (see also Scheme 7). Oxidations of 5β‐hydroxy‐B‐norcholestan‐3β‐yl acetate ( 9 ) with both hypoiodite‐forming reagents (Pb(OAc)₄/I₂ and HgO/I₂) proceeded similarly to the HgO/I₂ reaction of the corresponding 5α‐hydroxy analogue 8 . Photolytic Pb(OAc)₄ oxidation of 9 afforded, in addition to the (Z)‐ and (E)‐5,10‐seco 1(10)‐unsaturated ketones 10 and 11 , their isomeric 5,10‐seco 10(19)‐unsaturated ketone 22 , the acetal 5‐acetate 21 , and 5β,19‐epoxy derivative 23 (Scheme 9). Exceptionally, in the thermal Pb(OAc)₄ oxidation of 9 , the 5,10‐seco ketones 10, 11 , and 22 were not formed, the only reaction being the stereoselective formation of the 5,10‐ethers with the β‐oriented epoxy bridge, i.e. the (10R)‐enol ether 20 and (5S,10R)‐acetal 5‐acetate 21 (Scheme 8). Possible mechanistic interpretations of the above transformations are discussed.     

Crown Ether Phase Transfer Catalysts for An Ionic Polymerization of Bisphenol A / 4,4′‐Dichlorodiphenyl Sulfone

Various crown ethers were prepared and applied as phase transfer catalysts for the an ionic copolymerization of bisphenol A and 4,4′‐dichlorodiphenyl sulfone monomers with alkali salts, e.g., NaNH₂, NaOH and KOH, as initiators. The catalytic abilities of various crown ethers for the an ionic polymerization of bisphenol A / 4,4′‐dichlorodiphenyl sulfone were found to be in the order: 15‐crown‐5 ? monobenzo‐15‐crown‐5 > 18‐crown‐6 > Dicyclohexano‐18‐crown‐6 > Dibenzo‐18‐crown‐6 > 12‐crown‐4 with sodium amide (NaNH₂) as initiator. Sodium amide was shown to be a better initiator than NaOH or KOH with monobenzo‐ 15‐crown‐5 as a catalyst. Effects of solvents and temperature on the crown ether catalytic polymerization were also investigated. Dimethyl sulfoxide (DMSO) exhibited much better for the polymerization than other organic solvents, e.g., toluene, p‐xylene, dimethyl formamide and dioxane. Higher polymerization was found at higher temperatures and about 100% yield of poly(bisphenol A / sulfone) was obtained at 125 °C in 3 hr. The molecular weight of poly(bisphenol A / sulfone) as a function of reaction time was determined with gel permeation chromatography. Concentration effects of crown ether on % yield and molecular weight of poly(bisphenol A / sulfone) were also investigated and discussed.     

Complexing properties of 3′,5′‐disubstituted‐4′‐hydroxybenzyl armed monoaza‐12‐crown‐4 and armed monoaza‐15‐crown‐5 ethers and crystal structures of the alkali metal ion complexes

A series of monoaza‐15‐crown‐5 ethers (2b‐2h) having 4′‐hydroxy‐3′,5′‐disubstituted benzyl groups have been prepared by the Mannich reaction of 2,6‐disubstituted phenols with the corresponding N‐methoxymethylmonoaza‐crown ethers. Competitive transport through a chloroform membrane by 12‐crown‐4 derivatives (lithium, potassium and cesium) and 15‐crown‐5 derivatives (sodium, potassium and cesium) were measured under basic‐source phase and acidic‐receiving phase conditions. All ligands transported size‐matched alkali‐metal cations. Ligands 1h and 2h with two fluorine atoms in the side arm gave higher metal ion transport rates than those of dimethyl‐ (1a and 2a), diisopropyl‐ (1b and 2b), and butylmethyl‐ (1d and 2d) derivatives. X‐ray crystal structures of six alkali metal complexes with monoaza‐12‐crown‐4‐derivatives ( 1b‐LiSCN, 1b‐KSCN, 1c‐NaSCN, 1d‐LiSCN, 1f‐RbSCN and 1h‐LiSCN ) and three alkali metal complexes with 15‐crown‐5 derivatives ( 2b‐KSCN, 2c‐KSCN , and 2e‐KSCN ) along with crystal structures of some new ligands (1b, 1c, 1d, 1f, and 2c) are also reported. These X‐ray analyses indicate that the crystal structures of the alkali metal ion complexes of these new armed‐crown ethers changed depending on the substituents at the 3′‐ and 5′‐positions of the appended hydroxybenzyl arms.     

Pb(18‐crown‐6)Cl2 and Hg(18‐crown‐6)I2: Molecular Dihalides Trapped in a Crown Ether

Pb(18‐crown‐6)Cl₂ and Hg(18‐crown‐6)I₂ are obtained as transparent colourless crystals of needle and hexagonal shape, respectively, by isothermal evaporation of their dichloromethane solutions. Pb(18‐crown‐6)Cl₂ crystallizes with the trigonal crystal system [ , no. 148, a = b = 1176.3(2), c = 1191.8(3) pm, V = 1428.2(5) 10⁶·pm³, Z = 3] whereas Hg(18‐crown‐6)I₂ crystallizes with the orthorhombic crystal system (Pnma, no. 62, a = 1613.9(2) pm, b = 2822.2(5) pm, c = 841.3(1) pm, V = 3832(1)10⁶·pm³, Z = 8). Both compounds are characterized by linear MX₂ (HgI₂ or PbCl₂) molecular units which are encrypted by the crown ether. In both cases, the divalent metal ion resides in the middle of the crown ether resulting in a hexagonal bipyramidal coordination environment for the metal cations. The molecular symmetry comes close to D_3d. Hg(18‐crown‐6)I₂ and Pb(18‐crown‐6)Cl₂ differ in the way the single MX₂@18‐crown‐6 units are packed. Whereas the Hg(18‐crown‐6)I₂ molecules are arranged in a (distorted) cubic closest packing, the Pb(18‐crown‐6)Cl₂ molecules adopt a hexagonal closest packing.     

Synthese,Charakterisierung und Kristallstrukturen der Pseudohalogen‐Kronenether‐Komplexe [K([18]krone‐6)(X)(OPPh3)] (X = N3–, OCN– und SCN–)

Preparation, Characterisation, and Crystal Structures of the Pseudohalogen Crown Ether Complexes [K([18]crown‐6)(X)(OPPh₃)] (X = N₃^–, OCN^– and SCN^–) The potassium crown ether complexes [K([18]Crown‐6)(X)(OPPh₃)] (with X = N₃^–, OCN^– and SCN^–) can be obtained by reaction of KX with 18‐crown‐6 (1, 4, 7, 10, 13, 16‐hexaoxacyclooctadecane and triphenylphosphane in THF exposed to UV light. All crown ether complexes were characterized by means of vibrational spectroscopy and X‐ray diffraction. They crystallize in the rhombic pointgroup R3m with three molecules in the unit cell: [K([18]crown‐6) (N₃)(OPPh₃)] ( 1 ): lattice constants at 293 K: a = b = 14.213(2) Å; c = 13.951(2) Å; R₁ = 0.0249. [K([18]crown‐6)(OCN)(OPPh₃)] ( 2 ): a = b = 14.239(2) Å; c = 13.8927(14) Å; R₁ = 0.0257. [K([18]crown‐6)(NCS)(OPPh₃)] ( 3 ): a = b = 14.339(2) Å; c = 14.266(2) Å; R₁ = 0.0264.     

Neue Kronenether‐stabilisierte Oxoniumhalogenochalkogenate: [H3O(Dibromo‐benzo‐18‐Krone‐6)]2[Se3Br10] und [H5O2(Bis‐dibromo‐dibenzo‐24‐Krone‐8]2[Se3Br8]

Novel Oxonium Halogenochalcogenates Stabilized by Crown Ethers: [H₃O(Dibromo‐benzo‐18‐crown‐6)]₂[Se₃Br₁₀] and [H₅O₂(Bis‐dibromo‐dibenzo‐24‐crown‐8]₂[Se₃Br₈] Two novel complex oxonium bromoselenates(II,IV) and –(II) are reported containing [H₃O]⁺ and [H₅O₂]⁺ cations coordinated by crown ether ligands. [H₃O(dibromo‐benzo‐18‐crown‐6)]₂[Se₃Br₁₀] ( 1 ) and [H₅O₂(bis‐dibromo‐dibenzo‐24‐crown‐8]₂[Se₃Br₈] ( 2 ) were prepared as dark red crystals from dichloromethane or acetonitrile solutions of selenium tetrabromide, the corresponding unsubstituted crown ethers, and aqueous hydrogen bromide. The products were characterized by their crystal structures and by vibrational spectra. 1 is triclinic, space group (Nr. 2) with a = 8.609(2) Å, b = 13.391(3) Å, c = 13.928(3) Å, α = 64.60(2)°, β = 76.18(2)°, γ = 87.78(2)°, V = 1404.7(5) ų, Z = 1. 2 is also triclinic, space group with a = 10.499(2) Å, b = 13.033(3) Å, c = 14.756(3) Å, α = 113.77(3)°, β = 98.17(3)°, γ = 93.55(3)°. V = 1813.2(7) ų, Z = 1. In the reaction mixture complex redox reactions take place, resulting in (partial) reduction of selenium and bromination of the crown ether molecules. In 1 the centrosymmetric trinuclear [Se₃Br₁₀]^2? consists of a central Se^IVBr₆ octahedron sharing trans edges with two square planar Se^IIBr₄ groups. The novel [Se₃Br₈]^2? in 2 is composed of three planar trans‐edge sharing Se^IIBr₄ squares in a linear arrangement. The internal structure of the oxonium‐crown ether complexes is largely determined by the steric restrictions imposed by the aromatic rings in the crown ether molecules, as compared to complexes with more flexible unsubstituted crown ether ligands.