A new synthesis of phosphorofluoridates of biological interest. The reaction of phosphoroazolides with benzoyl fluoride

Phosphoroazolides, including nucleoside derivatives, can be converted smoothly into the corresponding phosphorofluoridates by reaction with benzoyl flouride. From these compounds oligonucleotides containing → P-F instead of → P-OH can be prepared.     

Butadienyloxiran-Dihydrooxepin-Isomerisierung. Ringerweiterungsreaktionen von sterisch fixierten und benzoanellierten Epoxyhexadienen durch 1,7-Elektrocyclisierung konjugierter Carbonyl-Ylide

Butadienyloxirane-Dihydrooxepine Isomerisation. Ring Expansion Reactions of Sterically Fixed and Benzoannelated Epoxyhexadienes by 1,7-Electrocyclisation of Conjugated Carbonyl Ylides Thermal ring cleavage of specifically substituted oxiranes results in the formation of conjugated carbonyl ylide intermediates which react by 1,5- and/or 1,7-electrocyclisation to give ring-expanded products. While the spirooxiranes 5t, 6t , and 12t are transformed, as expected, only into 2,3-dihydrofurans ( 21, 22, 50 ), the geometrically fixed compounds give rise to the formation of seven-membered ring isomers either partially ( 6c ), or predominantly ( 5c ), or exclusively ( 7 – 11, 12c ). 1,7-Dipolar cyclisations also take place with participation of one or even two aromatic double bonds ( 7 → 52, 8 → 53, 9 → 54, 12c → 57 , and 10 → 55, 11 → 56 , resp.) affording mono- and dibenzo-dihydrooxepines, respectively. The rearrangements of 5c to 27 and 6c to 28 show for the first time that the 8π-ring closure of 2-oxaheptatrienyl dipoles proceeds in the theoretically predicted conrotatory manner. The exclusive, i.e. periselective formation of dihydrooxepines during the thermolysis of compounds 7 – 11, 12c is explained by assuming a helical geometry of the dipolar intermediates in which the stereoelectronic situation is specially suitable for the – entropically less advantageous – 1,7-cyclisation process.     

Synthesis,Structure and Properties of C(X)NHP(Y) Fragment Containing Compounds

Abstract

N-(thio)carbonyl(thio)amidophosphate, their open-chain and crown-containing analogues with a C (X) NHP (Y) fragments are associated with intermolecular hydrogen bonds as C=X…H-N and P=Y…H-N or intramolecular hydrogen bonds of N-H…O(macrocycle). These compounds easily enter into alkylation reaction, are added according to C=N bonds of activated imines, take part in O → S and S → O exchanging reactions.     

Synthesis of 1,2,3-thiadiazole-5-carbaldehydes and their conversion into 6aδ4-Thia-1,2,5,6-tetraazapentalenes

A convenient method for the synthesis of the virtually unknown 1,2,3-thiadiazole-5-carbaldehydes consists in monobromination of the 5-methyl derivatives, followed by treatment with sodium azide and decomposition in concentrated sulfuric acid ( 6 → 7 → 9 → 10 ). These compounds can be transformed via methylation of the corresponding hydrazones 12 into 6aδ⁴-thia-1,2,5,6-tetraazapentalenes 13 .     

Synthesis and domino reactions of polymethylene-3-cyanopyridine-2(1Н)-thiones

A new and facile three-component method was developed for the synthesis of polymethylene-3-cyanopyridine-2(1Н)-thiones by the domino Knoevenagel → Michael → heterocyclization → dehydrogenation reaction from cycloalkanones, cyanothioacetamide, and polymethoxy-substituted benzaldehydes. The final dehydrogenation step was found to involve arylidenecyanothioacetamide. The resulting pyridinethiones and 4-chloroacetoacetic ester were introduced into the domino S_N2 → Thorpe-Ziegler → Guareschi-Thorpe reaction to synthesize tetracyclic dipyridothiophenes. Starting from these compounds, 8,9-polymethylenepyranothienodipyridines were also synthesized by the domino Knoevenagel → Michael → hetero-Thorpe-Ziegler reaction. Furthermore, a method for the synthesis of thienodipyridine annulated to the steroid skeleton is proposed.     

Heterotricyclodecane XXII 2-Aza-7-thia-isotwistane

2-Aza-7-thia-isotwistanes . 2-Aza-7-thia-isotwistanes were synthesized either starting from suitable 9-thiabicyclo[3.3.1]nonenes by olefin-amination ( 1 → 4 , 2 → 5 , 3 → 6 , 8 → 10 and 9 → 11 ) as well as by intramolecular substitution ( 25 → 26 ) or by molecular rearrangement starting from twistanes ( 21 → 19 and 22 → 10 ). From the isotwistanes thus obtained several other compounds ( 7 , 12 – 18 , 20 , 23 and 24 ) were prepared, too.     

Rearrangements and interconversions of heteroatom-substituted isocyanates, isothiocyanates, nitrile oxides, and nitrile sulfides, RX-NCY and RY-CNX

Isocyanates and isothiocyanates of the type RX-NCY (X and Y = O or S) and the isomeric nitrile oxides and nitrile sulfides RY-CNX are highly reactive compounds. A number of potential 1,4-shifts of substituent groups of the type R-Y-CNX → R-X-N═C═Y, 1,3-shifts R-C(═Y)-N═X → R-X-N═C═Y, and 1,2-shifts R-C(═Y)-N═X → R-Y-CNX have been evaluated computationally. The results obtained for the relatively new functional MPW1K and the well-established B3LYP, together with a triple-ζ quality basis set, are very similar. The 1,3- and 1,4-halogen shifts in the title compounds are usually highly exothermic and possess low activation barriers. 1,3-Aryl shifts are feasible for for 5e → 6e (Ar-CO-NSO(2) → Ar-SO(2)-NCO) with activation barriers of less than 40 kcal/mol. Additionally, several 1,3- and 1,4-hydrogen shifts and the 1,4-methyl-shift in methoxynitrile sulfide MeO-CNS to methylsulfenyl isocyanate MeS-NCO (4c → 6c) are potentially feasible. The 1,2-shift reactions 4b → 5b (HO-NCS → H-CS-NO) and 4c → 5c (Ar-O-CNS→ Ar-CO-NS) are good candidates for experimental observation with activation energies around 30 kcal/mol.     

Syntheses,Characterization, and Fluorescence Properties of Four Coordination Polymers based on Double Betaine Ligands

Four novel In³⁺ and Cd²⁺ based 1D coordination compounds constructed by double betaine ligands were synthesized and characterized structurally and optically. They assemble into 3D supra‐molecular architectures via different stacking or entanglement of 1D zigzag shaped chains, in which C–H ··· Cl and C–H ··· O hydrogen bonding interactions play a dramatic impact. Compound 1 displays a 1D + 1D → 3D four‐connect lvt net with 4² · 8⁴ topology. Compound 2 assembles into a 3D architecture by inclined stacking of the adjacent zigzag chains. Compound 3 displays a 2D + 2D → 3D inclined polycatenation based on the resulting 2D (6, 3) layers that constructed by 1D chains. Compound 4 displays a 3D supra‐molecular architecture based on 1D chains, which were connected via the hydrogen bonding. Meanwhile, four compounds emit in the range of visible region owing to the intra‐ligand π*→π and/or π*→n electron transition induced florescence.     

Theoretical Studies on the Electronic Structures and Spectral Properties of 4,4′-（Ethane-1,2-diylbis-（oxy））dibenzaldehyde and Its Polymorph

The ground state geometries, frontier molecular orbital properties, and absorption properties of 4,4′-(ethane-1,2-diylbis(oxy))dibenzaldehyde (EDO-DBDHD) and its polymorph have been studied theoretically. The density functional theory (DFT) method was employed to optimize the ground state geometries, and theoretical data reveal that EDO-DBDHD features the planar molecular conformations, in contrast to V-shaped structures of its polymorph, which agrees with the experimental data. Additionally, the absorption spectra of both compounds were predicted using time-dependent density functional theory (TDDFT). The calculated results show that the lowest lying absorption bands of these compounds have the transition configurations of HOMO → LUMO, resulting in the transition character of π→π*/n→π*. The transition of HOMO → LUMO+3 mainly contributes to the highest lying absorption bands of two compounds at 225 nm with the character of π→π*/n→π*.     

Synthesis of E-homoallylic alcohols, γ-hydroxyketones,and cyclopropyl ketones from 3-diphenylphosphinoyl (Ph2PO) propanols by acyl transfer

Carboxyl transfer (O→C) on 3-Ph₂PO propyl esters (9) gives an intermediate (10) from which the Ph₂PO group may be removed by the Horner-Wittig reaction or by Ph₂PO transfer (C→O) to give the title compounds.     

Substitutional mechanism of Ni into the wide-band-gap semiconductor InTaO4 and its implications for water splitting activity in the wolframite structure type

The mechanism of Ni substitution into the oxide semiconductor InTaO(4) has been studied through a combination of structural and spectroscopic techniques, providing insights into its previously reported photoactivity. Magnetic susceptibility and X-ray absorption near-edge spectroscopy (XANES) measurements demonstrate that nickel is divalent within the host lattice. The combined refinement of synchrotron X-ray and neutron powder diffraction data indicates that the product of Ni doping has the stoichiometry of (In(1-x)Ni(2x/3)Ta(x/3))TaO(4) with a solubility limit of x ≈ 0.18, corresponding to 12% Ni on the In site. Single-phase samples were only obtained at synthesis temperatures of 1150 °C or higher due to the sluggish reaction mechanism that is hypothesized to result from small free energy differences between (In(1-x)Ni(2x/3)Ta(x/3))TaO(4) compounds with different x values. Undoped InTaO(4) is shown to have an indirect band gap of 3.96 eV, with direct optical transitions becoming allowed at photon energies in excess of 5.1 eV. Very small band-gap reductions (less than 0.2 eV) result from Ni doping, and the origin of the yellow color of (In(1-x)Ni(2x/3)Ta(x/3))TaO(4) compounds instead results from a weak (3)A(2g) → (3)T(1g) internal d → d transition not associated with the conduction or valence band that is common to oxide compounds with Ni(2+) in an octahedral environment.     

Synthesis and Application of Some Dianilinosilanes,Bis (Trimethylsilyl) Phenylenediamines and Dialkyl Benzo-1,3,2-Diazasilolines as Antioxidants

Negative hyperconjugation of the type n_N→σ* is responsible for the planar or almost planar geometry at nitrogen in certain S–N compounds.     

Utilisation du 13C en Spectrométrie de Masse: Etude de la Fragmentation de Disaccharides

Twenty-nine α,β-(1 → 3) and (1 → 4) or β-(1 → 6) disaccharides, in the glucose series were analysed by electron impact mass spectrometry. In addition to the known mechanism, a few ¹³C labelled compounds led us to suggest that the ion c was formed from the reducing unit B and the C-1′ of the non-reducing residue A, while A was the starting point for rearrangement and fragmentation processes.     

Synthesis and anti-fungal activity of seven oleanolic acid glycosides

In order to develop potential anti-fungal agents, seven glycoconjugates composed of α-L-rhamnose, 6-deoxy-α-L-talose, β-D-galactose, α-D-mannose, β-D-xylose-(1→4)-6-deoxy-α-L-talose, β-D-galactose-(1→4)-α-L-rhamnose, β-D-galactose-(1→3)-β-D-xylose-(1→4)-6-deoxy-α-L-talose as the glycone and oleanolic acid as the aglycone were synthesized in an efficient and practical way using glycosyl trichloroacetimidates as donors. The structures of the new compounds were confirmed by MS, 1H-NMR and 13C-NMR.Preliminary studies based on means of mycelium growth rate, indicated that all the compounds possess certain fungicidal activity against Sclerotinia sclerotiorum (Lib.) de Bary, Rhizoctonia solani Kuhn, Botrytis cinerea Pers and Phytophthora parasitica Dast.     

Kinetics of direct and reverse polymorphic transformations in molecular crystals of energetic compounds

The β → γ polymorphic transformation (PT) in polycrystalline 1,1-diamino-2,2-dinitroethylene (DADNE) was studied by isothermal calorimetry. The kinetics of the β → γ PT, like that of the α → β process studied earlier, follows the first-order autocatalytic equation. The rate constants and activation energy of the process were determined. The kinetics of the reverse β → α and γ → α PTs in DADNE was studied by IR spectroscopy. The rates of the β → α and γ → α PTs follow first-order kinetics with the rate constants that depend on morphological features of the crystals. The general features of the kinetics of direct and reverse polymorphic transformations in molecular crystals of energetic compounds are discussed.     

Excited electronic states of the fluorobenzenes by variable angle electron impact spectroscopy

Electron-impact excitation spectra of benzene, fluorobenzene, o-difluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, pentafluorobenzene, and hexafluorobenzene have been measured at impact energies of 50 eV and either 25 eV or 30 eV, and scattering angles from 5° to 80°. Each molecule shows an absorption maximum at about 3.9 eV corresponding to a singlet → triplet, π → π^*, transition. In benzene, fluorobenzene, o-difluorobenzene, and 1,3,5-trifluorobenzene, an additional singlet → triplet transition was detected at about 5.6 eV. Three singlet → singlet transitions analogous to the 4.90, 6.20, and 6.95 eV transitions in benzene are seen in each of the fluorine-substituted molecules. The more highly substituted compounds exhibit an additional singlet → singlet transition that is most clearly observed in the hexafluorobenzene spectrum with a peak at 5.32 eV.     

Design,Synthesis, and Structural Analysis of Divalent NI Compounds and Identification of a New Electron‐Donating Ligand

The dative‐bond representation (L→E) in compounds with main group elements (E) has triggered extensive debate in the recent past. The scope and limits of this nonclassical coordination bond warrant comprehensive exploration. Particularly compounds with (L→N←L′)⁺ arrangement are of special interest because of their therapeutic importance. This work reports the design and synthesis of novel chemical species with the general structural formula (L→N←L′)⁺ carrying the unusual ligand cyclohexa‐2,5‐diene‐4‐(diaminomethynyl)‐1‐ylidene. Four species belonging to the (L→N←L′)⁺ class carrying this unconventional ligand were synthesized. Quantum chemical and X‐ray diffraction analyses showed that the electronic and geometric parameters are consistent with those of already reported divalent N^I compounds. The molecular orbital analysis, geometric parameters, and spectral data clearly support the L→N and N←L′ interactions in these species. The newly identified ligand has the properties of a reactive carbene and high nucleophilicity.     

Cycloaddition of N-acylimines with cyclobutadienes

N-Acylimines (2) possess the characteristics of both hetero-1,3-dienes and dienophiles. They react with the kinetically stabilised cyclobutadienes 1 to form 4-aza-2-oxabicyclo[4.2.0]octa-3,7-dienes (3) and/or 2-azabicyclo[2.2.0]hex-5-enes (4). Compounds of the type 3 undergo acid-catalysed isomerisation to give compounds 4. Homocyclopropenylium intermediates of the type 5 are supposed to be involved in both processes (1 + 2 → 3 + 4 and 3 → 4).     

Photochemische Reaktionen. 68. Mitteilung. Die Photoisomerisierung von α,β-ungesättigten γ,δ-Epoxyketonen: 9α, 10α- und 9β, 10β-Oxido-3-oxo-17β-acetoxy-Δ4-östren

Irradiation in the n→π* absorption band of the α,β-unsaturated γ,δ-epoxyketone 5 in ethanol at ?65° exclusively afforded the rearranged ene-dione 13 , whereas at + 24° under otherwise unchanged reaction conditions or upon triplet sensitization with Michler's ketone and with acetophenone at + 24° essentially identical mixtures of 13 (major product), 14 , and 15 were obtained. Selective π→π* excitation of 5 at ?78° and + 24° led to similar product patterns. The 9β,10β-epimeric epoxyketone 7 selectively isomerized to 14 and 15 at + 24° and n → π* or π → π* excitation. Neither the epoxyketones 5 and 7 nor the photoproducts 13–15 were photochemically interconverted. In separate photolyses each of the latter gave the double bond isomers 16 , 18 , and 19 , respectively. Cleavage of 13 to the dienone aldehyde 17 competed with the double bond shift ( → 16 ) when photolyzed in alcoholic solvents instead of benzene. The selective transformations 5 → 13 (at ?65° and n → π* excitation) and 7 → 14 + 15 are attributed to stereoelectronic factors facilitating the skeletal rearrangements of the diradicals 53 and 55 , the likely primary photoproducts resulting from epoxide cleavage in the triplet-excited compounds 5 and 7 , via the transition states 54 , 56 , and 57 . The loss of selectivity in product formation from 5 at higher temperature and n → π* excitation or triplet sensitization is explicable in terms of radical dissociation into 58 and 59 increasingly participating at the secondary thermal transformations of 53 . The similar effect of π → π* excitation even at ?78° indicates that some of the π,π* singlet energy may become available as thermal activation energy. It is further suggested that the considerably lesser ring strain in 14 and 15 , as compared with 13 , is responsible that selectivity in product formation from 7 is maintained also at +24° and at π → π* excitation.     

Xanthone O‐Glycosides from the Roots of Pteris Multifida

Two new xanthone glycosides and six known compounds were isolated from the roots of Pteris multifida. Based on spectroscopic and chemical methods, the structures of the new compounds were elucidated as 1‐hydroxy‐4,7‐dimethoxy‐8‐(3‐methyl‐2‐butenyl)‐6‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐[β‐D‐glucopyranosyl‐(1→3)]‐β‐D‐glucopyranosylxanthone ( 1 ), and 1,3‐dihydroxy‐7‐methoxy‐8‐(3‐methyl‐2‐butenyl)‐6‐O‐α‐L‐rhamnopyranosyl‐(1 →2)‐[β‐D‐glucopyranosyl‐(1→3)]‐β‐D‐glucopyranosylxanthone ( 2 ), respectively.