Dianionic complexes with hexacoordinate silicon(IV) or germanium(IV) and three bidentate ligands of the salicylato(2–) type: Syntheses and structural characterization in the solid state and in solution

Reaction of tetramethoxysilane or tetramethoxygermane with salicylic acid and morpholine (molar ratio 1:3:2) in tetrahydrofuran yielded morpholiniummer-tris[salicylato(2–)-O¹,O³]silicate(mer -5) and morpholiniummer-tris[salicylato(2–)-O¹,O³]germanate (mer-8), respectively. Treatment of tetramethoxysilane with 5-chlorosalicylic acid and piperidine (molar ratio 1:3:2) in tetrahydrofuran afforded piperidinium mer-tris[5-chlorosalicylato(2–)-O¹,O³]silicate–ditetrahydrofuran (mer-6·2THF). Triethylammonium mer-tris[3-methylsalicylato(2–)-O¹,O³]silicate (mer-7) was obtained analogously by reaction of tetramethoxysilane with three molar equivalents of 3-methylsalicylic acid and two molar equivalents of triethylamine in dichloromethane/diethyl ether. The racemic compounds mer-5, mer-6· 2THF,mer-7, and mer-8 were characterized by elemental analyses (C, H, N), single-crystal X-ray diffraction, as well as solid-state (²⁹Si) and solution(¹H, ¹³C, ²⁹Si) NMR studies. The structural characterizationwas complemented by computational studies (HF studies, TZVP level) of thefac- and mer-tris[salicylato(2–)-O¹,O³]silicatedianion. In addition, the behavior of mer-7 in solution was studied by VT ¹HNMR experiments.     

Synthesis of (zinc(II) phthalocyanine)-containing cellulose derivative using phthalocyanine-ring formation reaction

2,3-Di-O-myristyl-6-O-(zinc(II) phthalocyaninyl) cellulose (5) was synthesized from cellulose (1) by five reaction steps via 6-O-(3′,4′-dicyanophenyl)-2,3-di-O-myristyl cellulose (4). The key reaction was phthalocyanine-ring formation on a cellulose backbone, that is, the reaction of compound 4 with o-phthalodinitrile in the presence of hexamethyldisilazane and zinc acetate in DMF afforded to compound 5 in 35.4 % yield. Consequently, the degree of substitution with phthalocyanine moieties of compound 5 was 0.38. The LB monolayer film of compound 5 on an indium tin oxide (ITO) electrode was found to show photocurrent generation performance at 680 nm.     

Preparation and structures of some new 1H-pyrazole derivatives

Some new 3,5-diaryl-1H-pyrazoles were prepared from aryl methyl ketones via Claisen condensation with aromatic esters and followed by cyclization with hydrazine monohydrate. Their structures were confirmed by IR, ¹H NMR spectroscopy, mass spectrometry and elemental analysis. The X-ray structure for 3(5)-(4-tert-butylphenyl)-5(3)-(4-methoxyphenyl)-1H-pyrazole (2b) was presented. The results show that compound 2b exists as tautomers I and II, and its molecules are connected by the N–H···N intermolecular hydrogen bonds to form cyclic dimers consisting of the tautomers I and II.     

Strukturelle Abwandlungen an Nukleotiden,Nukleosiden und Nukleosidbasen mit β-Acylvinylphosphoniumsalzen

β-Acetylvinyl-triphenylphosphonium bromide1 reacts with CMP to form the 3,N⁴-etheno-derivative {[6-(5′-phosphoribofuranosyl)-2-methyl-5-oxo-imidazo [1.2-c]pyrimidin-3-yl]-methyl}triphenyl-phosphonium bromide (2). Guanine affords mainly the lin. condensation product [(6-methyl-9-oxo-imidazo[1.2-a]-purin-7-yl)-methyl]triphenylphosphonium bromide (3) and the angular tricyclic product [(6-methyl-9-oxo-imidazo[2.1-b]purin-5-yl)-methyl]-triphenylphosphonium bromide (4). For comparison we synthesized the angular condensed heterocycle5, (6.8-dimethyl-9-oxo-imidazo[2.1-b]purin-5-yl)-methyl]triphenylphosphonium bromide, by reaction of 1-methylguanine with1, and the corresponding linear derivative6 [(4.6-dimethyl-9-oxo-imidazo[1.2-a]purin-7-yl)-methyl]-triphenylphosphoniumbromide from 3-methylguanine and1. AHofmann-type degradation of3 with the anion of diethyl malonate led to7, diethyl (6-methyl-9-oxo-imidazo[1.2-a]purin-7-yl)-methylmalonate, a compound whose structure resembles some Y-bases in t-RNA.Wittig reaction of the silylated nucleoside derivative8 a {[2-methyl-5-oxo-6-(2′.3′.5′-tris-trimethylsilyl)-ribofuranosyl-imidazo[1.2-c]pyrimidin-3-yl]methyl}-triphenylphosphonium bromide, with C₆H₅CHO resulted in the 2-methyl-3(ω-styryl)-6[2′.3′.5′-tris-(trimethylsilyl)]ribofuranosyl-imidazo[1.2-c] pyrimidin-5-one (9).     

Transformations of ortho-quinones in the γ-radiolysis of their solutions in cyclohexane

The transformations of 4-tert-butyl-1,2-benzoquinone (I), 3,5-di-tert-butyl-1,2-benzoquinone (II), and 4-methoxy-5-tert-butyl-1,2-benzoquinone (III) in deaerated cyclohexane solutions under exposure to γ-radiation were studied. It was found by chromatography-mass spectrometry and ¹H and ¹³C NMR spectroscopy that the addition of cyclohexyl radicals at the C=O bond in compounds I–III resulted in monoalkyl ethers, whereas cyclic ketal XXI was also formed in the case of compound II. Moreover, quinone I afforded mixed O-and C-alkylation products, and the adduct of cyclohexyl radicals and quinone II at the C=C bond was the source of dimeric products.     

Benzoylacetonate and its fluorinated derivatives as ligands for Co(II) complexes: the effect of the presence of fluorine atoms on the crystal packing

The influence of the introduced fluorine atoms to diketonato backbone exerted on the crystal packing was studied on cobalt(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionato-κ ² O,O′) compounds with pyridine (1), 2,2′-bipyridine (2) and 1,10-phenanthroline (4), and cobalt(II) bis(benzoylacetonato-κ ² O,O′) compound with 2,2′-bipyridine (3). The solid-state structures of 1–4 were determined by single crystal X-ray analysis. The coordination of Co(II) is octahedral in all four compounds. The differences in crystal packing of 1 with regard to the known complexes with non-fluorinated analogue and 4,4,4-trifluoro-1-(4-fluorophenyl)butane-1,3-dionate were observed. Unit cell parameters of 2·½C₇H₈ and 3·½C₇H₈ slightly differ, but they have similar crystal packing dominated by the π–π interactions. Strong π–π interactions and weak C–H···π(arene) and C–F···π(arene) interactions are present in 2–4, while no significant intermolecular interactions are present in 1.     

Syntheses and spectroscopic characterization of double-armed benzo-15-crown-5 derivatives and their sodium and potassium complexes

A series of new benzo-15-crown-5 derivatives (1–6) containing formyl and imine groups were prepared. New formyl crown ethers (1 and 2) were prepared by reaction of 4′,5′-bis(bromomethyl)benzo-15-crown-5 with 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) and 2-hydroxy-5-methoxybenzaldehyde in the presence of NaOH. New Schiff bases (3–6) were synthesized by the condensation of corresponding aldehydes with 1,3-diaminopropane and 1,4-diaminobutane. Sodium and potassium complexes (1a–6a and 1b–6b) of the crown compounds forming crystalline complexes of 1:1 (Na⁺:ligand) and 1:2 (K⁺:ligand) stoichiometries were also synthesized. The structures of the aldehydes 1 and 2, imines 3–6 and complexes (1a–3a and 1b–3b) were confirmed on the basis of elemental analyses, IR, ¹H- and ¹³C-NMR, and mass spectroscopy.     

Watson–Crick versus imidazopyridopyrimidine base pairs: theoretical study on differences in stability and hydrogen bonding strength

Matsuda and coworkers demonstrated that imidazopyridopyrimidine nucelobases (N ^N , O ^O , N ^O , tO ^O , and O ^N ) can mimic Watson–Crick nucleobase in forming H-bonds in DNA double helix. In the present study, we address the question about the strengths of the H-bonds in imidazopyridopyrimidine base pairs compared to those in Watson–Crick ones by focusing particularly on the nature of these interactions. Optimized structures of imidazopyridopyrimidine, imidazopyridopyrimidine–Watson–Crick, and Watson–Crick base pairs are obtained at the DFTB3LYP/6-311++G (d,p). The nature and strength of the intramolecular H-bonds in these base pairs have been investigated based on natural bond orbital (NBO method) to consider the effect of charge transfer, “atoms-in-molecules” (AIM) topological parameters, and decomposition of the interaction energies using the energy decomposition analysis (EDA). These investigations imply that N ^N –O ^O and N ^O –O ^N can form base pairs with four H-bonds (most stable than those of Watson–Crick base pairs) when they incorporated into DNA double helix. Furthermore, it can be deduced that O ^N and N ^N nucleobases form energetically more favorable pairs with adenine and guanine than the normal Watson–Crick counter parts. These results can be helpful for the stabilization and regulation of a variety of new base-pairing motif of DNA structures.     

Alkylation of 1-hydroxy-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 5,7-dioxide

Alkylation of 1-hydroxy-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 5,7-dioxide 1 and its silver salt 10 with different alkylating agents (diazomethane, diazoacetone, bromoacetone, α-bromoacetophenone, methyl iodide, methyl vinyl ketone) was studied. Alkylation of compound 1 with diazo compounds and salt 10 with halocompounds results predominantly in O-alkylation products, 1-alkoxy-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 5,7-dioxides. The Michael reaction of compound 1 with methyl vinyl ketone involves the triazole nitrogen atom to give 1-(3-oxobutyl)-1H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 3,4,6-trioxide. The structures of the compounds synthesized were established by ¹H, ¹³C, ¹⁴N NMR spectroscopy and mass spectrometry.     

The synthesis of some new imidazole and triazole derivatives: crystal Structure and DFT-TDDFT investigation on electronic structure

A series of new N′-3-(1H-imidazol-1-yl)propylcarbamoyl-4-halogenebenzo hydrazonate (3a–b) were obtained by reaction Ethyl 2-((4-halogene phenyl) (ethoxy) methylene) hydrazinecarboxylate (1) and N-(3-aminopropyl)imidazole (2) at 120–140 °C. Compounds (4a–b) were obtained by the reaction compound 1 and N-(3-aminopropyl)imidazole (2) at 160–180 °C. The structures of compounds 3,4 have been inferred through UV–Vis, IR, ¹H/¹³C NMR, mass spectrometry, elemental analyses, and X-ray crystallography. DFT level 6-31G (d) calculations provided structural information. The electronic structure of compound 3a has been studied by DFT level 6-31G (d) calculations using the X-ray data. The results are accordance with X-ray data.     

Naphthologs of overcrowded bistricyclic aromatic enes: (E)-bisbenzo[a]fluorenylidene

(E)-11H-Bisbenzo[a]fluorenylidene (E-6) was synthesized by Barton’s double extrusion diazo-thione coupling method from 11H-benzo[a]fluoren-11-thione (11) and 11-diazo-11H-benzo[a]fluorene (13). The reaction is probably thermodynamically controlled; in the event that the less stable Z -6 is also formed, it would rapidly undergo Z → E diastereomerization to give E -6. The B3LYP/6-311G(d,p) calculated diastereomerization barrier for Z -6 → E -6 is ΔG ₂₉₈ = 57.0 kJ/mol (13.6 kcal/mol). The calculated equilibrium constant K _eq(E -6 → Z -6) = 92:8 (at 298 K) is indicative of a marked diastereoselectivity of the reaction leading to E -6. The structure of E-6 was established by ¹H-NMR and ¹³C-NMR spectroscopies and by X-ray analysis. PAE E-6 crystallizes in the monoclinic space group C2/c. The unit cell of the crystal structure E -6 contains eight molecules, arranged as four pairs of enantiomers. PAE E -6 adopts a twisted conformation with the pure twist of the central C¹¹=C^11′ bond ω = 39°. The dihedral angle ν in E -6 is 60.6°, which is significantly higher than the respective dihedral angle in PAEs Z -6, 2, E -7, Z -7, 14, and 15. The large syn-pyramidalization angles at C¹¹ and C^11′ (χ = 12.6° and 14.8°) of E-6 indicates the enhanced strain in the fjord regions of the molecule. The enhanced twist is primarily attributed to the double benzo[a]annelation of the bifluorenylidene moiety at the fjord regions. The B3LYP/6-311G(d,p) calculated structure of E -6 is in a very good agreement with the experimental X-ray structure. PAE E -6 adopts a twisted conformation in solution, with the downfield chemical shift of H¹/H^1′ (8.31 ppm); H¹⁰/H^10′ (δ = 7.20 ppm) and H⁹/H^9′ (δ = 6.86 ppm) in E -6 are positioned above the planes of the opposing naphthalene rings. PAEs E -6 and Z -6 are significantly higher in energy than their corresponding benzo[b]annelated isomers E -7 and Z -7.     

Preparation and reactions of optically active cyanohydrins using the (R)-hydroxynitrile lyase from Prunus amygdalus

Cyanuration of 2-naphthaldehyde (1) and 5-methyl-2-furaldehyde (2) yielded the racemic 2-hydroxy-2-(β-naphthyl)ethanenitrile (R,S)-3 and 2-hydroxy-2-(5-methyl-2-furyl)ethanenitrile (R,S)-5, respectively. The same reaction can be completed by using acetone cyanohydrin (4) as a transcyanating agent. The optically active (R)-3 and (S)-5 could be respectively obtained by hydrocyanation of 1 and 2 using (R)-hydroxynitrile lyase (R)-PaHNL [EC 4.1.2.10] from almonds (Prunus amygdalus) as a chiral catalyst. Cyanohydrins 3 and 5 in their racemic and optically active forms undergo a number of transformations which involve either the hydroxyl group or the cyanide function. Moreover, derivatization of 3 and 5 with (S)-Naproxen®chloride (S)-14 gave the respective diastereoisomers. The optical activity of (R)-3 and (S)-5 as well as their derivatives were recorded. The postulated structures for the new products were supported with compatible elementary and spectroscopic (IR, ¹H NMR, ¹³C NMR, MS, and single crystal X-Ray crystallography) analyses. The antimicrobial activity of some selected racemic new products and their respective optically active analogues were also undertaken.     

Comparative investigation of the copper(II) complexes of (R)-, (S)- and (R,S)-1-phenyl-N,N-bis(pyridine-3-ylmethyl)ethanamine along with the related complex of (R,S)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine. Synthetic, magnetic, and structural studies

The interaction of the enantiopure (R)- and (S)-1-phenyl-N,N-bis(pyridine-3- ylmethyl)ethanamine ligands, R-L ¹ and S-L ¹ , with copper(II) chloride followed by addition of hexafluorophosphate resulted in the isolation of the corresponding enantiomeric complexes [Cu(R-L ¹ )Cl](PF₆) (1), [Cu(S-L ¹ )Cl](PF₆) (2) and [Cu(S-L ¹ )Cl](PF₆)??0.5Et₂O (3), in which dimerization occurs through two long Cu??????Cl interactions, the ??-chloro bridges being thus strongly asymmetric. The organic ligand is bound to the metal centre via its N₃-donor dipyridylmethylamine fragment in a planar fashion, such that each copper centre is in a square planar environment (or distorted square pyramidal with a long axial bond length if the additional interaction is considered). When R,S-L ¹ was employed in a parallel synthesis, the similar racemic complex [Cu(R,S-L ¹ )Cl](PF₆)??0.5MeOH (4) was obtained, in which the L ¹ ligands in each dimeric unit have opposite hands. In contrast to the complexes of L ¹ , the reaction of Cu(II) chloride with the related ligand, (R)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine (R-L ² ), yielded the mononuclear complex [Cu(R,S-L ² )Cl₂] (5), displaying a distorted square pyramidal coordination geometry. The structure of this product along with its corresponding circular dichroism spectrum revealed that racemisation of the starting R-L ² ligand has occurred under the relatively mild (basic) conditions employed for the synthesis. A temperature-dependent magnetic studies of the complexes 1, 2 and 5 indicate that a week ferromagnetic interaction is operative in each dicopper core in 1 and 2 with 2J?=?1.2?cm^?1. On the other hand, a week antiferromagnetic intermolecular interaction is operative for 5.     

Novel redox receptors for ion-pair and α-amino acid: synthesis and complexation properties of calix[4]arene derivatives bearing large conjugated ferrocene groups

By reacting calix[4]arene 1,3-bi-hydrazide derivative (2) with formacylferrocene in “1?+?2” condensation mode, novel calix[4]arene derivative bearing two conjugated ferrocene groups (3) was obtained in yield of 88%. By reacting 1,3-bi-substituted [2-(p-formylphenyloxy)ethyloxy]-p-tert-butylcalix[4]arene (5) with 1,1′-diacetylferrocene hydrazone (4) in “1?+?1” condensation mode, novel calix[4]arene derivative with 1,3-substituted large conjugated ferrocene bridge (6) was synthesized in yield of 83%. The structures and conformations of new compounds were confirmed by elemental analyses, IR spectra, ESI-MS, ¹H NMR, etc. The electrochemical cyclic voltammetry experiments revealed that compounds 3 and 6 possessed excellent reversible electrochemical properties. The ¹H NMR titration study showed that compound 6 possessed excellent complexation abilities for NaH₂PO₄ and glycine in 1:1 host–guest complex with the association constants of 3,850 and 2,460?M^?1, respectively.     

Theoretical Study of the Solvent Effect on the Methyltrioxorhenium/Hydrogen Peroxide System

The effect of solvent on the stability and reactivity of methyltrioxorhenium (MTO) for activation of hydrogen peroxide (H₂O₂) was investigated theoretically. The possible geometries for all Re complexes present in this system, MTO, monoperoxo complexes [A: MeReO₂(η ²–O₂) and A·H ₂ O: MeReO₂(η ²–O₂)(H₂O)], and bisperxo complexes [B: MeReO(η ²–O₂)₂ and B·H ₂ O: MeReO(η ²–O₂)₂(H₂O)] were calculated. Based on the theoretical calculations, species A lacks coordinated water while species B·H ₂ O definitely has water coordinated to the Re. The changes of thermodynamic parameters (ΔH and ΔG) for six reactions in the MTO/H₂O₂, system including formation of mono- and bisperoxo complexes, were determined.     

Characterization and analysis of structural isomers of dimethyl methoxypyrazines in cork stoppers and ladybugs (Harmonia axyridis and Coccinella septempunctata)

The three constitutional isomers of dimethyl-substituted methoxypyrazines: 3,5-dimethyl-2-methoxypyrazine 1; 2,5-dimethyl-3-methoxypyrazine 2; and 2,3-dimethyl-5-methoxypyrazine 3 are potent flavor compounds with similar mass spectrometric, gas chromatographic, and nuclear magnetic resonance spectroscopic behavior. Therefore, unambiguous analytical determination is critical, particularly in complex matrices. The unequivocal identification of 1–3 could be achieved by homo- and heteronuclear NMR correlation experiments. The observed mass fragmentation for 1–3 is proposed and discussed, benefitting from synthesized partially deuterated 1 and 2. On common polar and apolar stationary phases used in gas chromatography (GC) 1 and 2 show similar behavior whereas 3 can be separated. In our focus on off-flavor analysis with respect to wine aroma, 1 has been described as a “moldy” off-flavor compound in cork and 2 as a constituent in Harmonia axyridis contributing to the so-called “ladybug taint,” whereas 3 has not yet been described as a constituent of wine aroma. A successful separation of 1 and 2 could be achieved on octakis-(2,3-di-O-pentyl-6-O-methyl)-γ-cyclodextrin as stationary phase in GC. Applying heart-cut multidimensional GC analysis with tandem mass spectrometric detection we could confirm the presence of 1 as a “moldy” off-flavor compound in cork. However, in the case of Harmonia axyridis, a previous identification of 2 has to be reconsidered. In our experiments we identified the constitutional isomer 1, which was also found in Coccinella septempunctata, another species discussed with respect to the “ladybug taint.” The analysis of such structurally related compounds is a demonstrative example for the importance of a chromatographic separation, as mass spectrometric data by itself could not guarantee the unequivocal identification.     

Microwave promoted improved regioselective synthesis of 1H,3H,6H[2]benzopyrano[4,3-d]pyrimidine-2,4-diones by radical cyclisation

In this work, two new effective methodologies have been adopted for the preparation of 5-(2′-bromobenzyloxy)pyrimidine-2,4-diones 6(a–k). In the first methodology, 5-hydroxy uracils 4(a–f) were alkylated with 2-bromobenzyl bromide 5a or 2-bromo-5-methoxy benzyl bromide 5b under phase transfer catalysis condition using lithium hydroxide/tetrabutyl ammonium bromide in N,N-dimethylformamide at 45 °C, and in the second method, the microwave irradiation (MWI) protocol has been exploited by mixing 5-hydroxy uracils 4(a–f) with 30 % excess of 2-bromobenzyl bromide 5a or 2-bromo-5-methoxy benzyl bromide 5b. A catalytic amount of TBAB and potassium carbonate was added and irradiated in an open Erlenmeyer flask in a microwave oven for 3–12 min. The tributyltin hydride-mediated radical cyclisation of 6(a–k) was carried out under MWI to generate 1H,3H,6H[2]benzopyrano[4,3-d]pyrimidine-2,4-diones 7(a–k) in 80–89 % yield, and the reaction time was shortened compared to the previously reported conventional radical cyclisation method.     

Syntheses, spectroscopic characterization and metal ion binding properties of benzo-15-crown-5 derivatives and their sodium and nickel(II) complexes

New benzo-15-crown-5 derivatives containing nitro, amine and imine groups were prepared. Nitro compound (1) was prepared after the reaction?4′,5′-bis(bromethyl)benzo-15-crown-5 and o-nitrophenol in the presence of NaOH. After reduction process by using hydrazine hydrate and Pd/C amine compound (2) was formed. New crown ether imine compounds (3–5) were synthesized by the condensation of corresponding crown ether diamine (2) with salicylaldehyde derivatives. Sodium complexes of the crown compounds (1a–5a) form crystalline 1:1 (Na⁺: ligand) complexes with sodium perchlorate. Nickel(II) complexes (3b–5b) with 1:1 (Ni²⁺:ligand) stoichiometries were also been synthesized from the Schiff bases (3–5). The results indicated that the Schiff base ligands coordinated through the azomethine nitrogen and phenolic oxygen. The extraction ability of compounds (1, 3, 4 and 5) were also evaluated in chloroform by using several alkali and transition metal picrates such as Li⁺, Na⁺, K⁺, Cr³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pb²⁺.     

Preparation of Langmuir–Blodgett monolayer films of (zinc(II) phthalocyanine)-containing cellulose derivative; the use of 2,3-di-O-myristyl cellulose as a scaffold

The 6-O-phthalocyanine cellulose derivative, 2,3-di-O-myristyl-6-O-[p-(9(10),16(17),23(24)-tri-tert-butyl-2-zinc(II)phthalocyaninyl-benzoyl)cellulose (8e) was synthesized in a high yield with the degree of substitution of 0.33 for the phthalocyaninyl group (DS_{phthalocyanine}) via the esterification of 2,3-di-O-myristyl cellulose (1) with the mono-substituted phthalocyanine derivative ([9(10),16(17),23(24)-tri-tert-butyl-2-[4-(carboxy)phenoxy]phthalocyaninato]zinc(II), 7). A chloroform solution of compound 8e was more stable under illumination than that of low molecular weight phthalocyanine, [2(3),9(10),16(17),23(24)-tetrakis(tert-butyl)phthalocyaninato]zinc(II). Langmuir–Blodgett (LB) monolayer films of compound 8e were prepared on a variety of different substrates using the vertical dipping method with an annealing time of 5 min. An LB monolayer film of compound 8e on an indium tin oxide (ITO) electrode exhibited a photocurrent generation performance in the range of 600–700 nm. The photocurrent density of the film composed of 8e at 680 nm was better than that of 2,3-di-O-myristyl-6-O-(zinc(II) phthalocyaninyl) cellulose (3) which was the corresponding phthalocyanine-containing cellulose synthesized through a phthalocyanine-ring forming reaction on the cellulose backbone according to an existing procedure.     

Stereoselective (exo-specific) synthesis, dynamic 1H NMR and quantum chemical conformational and configurational analysis of norbornene-aziridine-E-imidoyl system

Stereoselective (exo-specific) synthesis, dynamic ¹H NMR and computational analysis of exo-N??-{3-azatricyclo[3.2.1.0.^2,4]oct-3-yl)mesithyloxy)methylene}-1-benzensulfunamide (3) were investigated. Aziridine nitrogen inversion gives rise to two sets of configurations where the N-substituent is Syn (S) or Anti (A) to C7 of the norbornyl ring. At lower temperature, the proton signals of aziridine exo-E-3 decoalesces to show two syn conformers and one anti conformer (exo-E-3 ^{1 S} ? $ \leftrightharpoons $ ?exo-E-3 ^{2 S} ? $ \leftrightharpoons $ ?exo-E-3 ^{3 A} ) with ratio of 60:20:20, respectively. Experimentally, the Gibbs free energy of activations [??G ^? (kcal/mol) ?±?0.08] were calculated 11.96, 12.45 for 3 isomerizations. The standard Gibbs free energy (??G ^o kcal/mol) 0.174, 0, 0.174, and 0.298 at 213?K and energy minimum 6.64, 4.77 and 1.78 were calculated for 3 ^1S? $ \leftrightharpoons $ ?3 ^2S, 3 ^2S? $ \leftrightharpoons $ ?3 ^{3 A} , 3 ¹ S? $ \leftrightharpoons $ ?3 ^{3 A} isomerizations, respectively. The enthalpy (??H ^?, kcal/mol) and entropy (??S ^?, cal?mol^?1?K^?1) of activation for the nitrogen inversion of aziridine of 3 were calculated 11.2 and ?0.80, respectively.