SYNTHESIS AND CONFORMATIONAL STUDIES OF A NUMBER OF SATURATED BICYCLIC SIX-MEMBERED RING PHOSPHITES

Abstract

An ¹H NMR study of the conformation of the dioxaphosphorinane ring of a number of diastereoisomeric bicyclic saturated six-membered ring phosphites (3ab-10ab) has been performed. The dioxaphosphorinane ring of these phosphites is transannelated with a tetrahydrofuran, cyclopen-tane, tetrahydropyran or cyclohexane ring. The substituent on the phosphorus atom is a methoxy or phenoxy group. It is shown that the cis isomers 3a-10a prefer a chair conformation of the dioxaphosphorinane ring, independent of the substituent on the phosphorus atom and of the nature of the transannelated ring. In contrast, for the trans isomers 3b-10b a twist rather than a chair conformation of the dioxaphosphorinane ring is preferred. The fraction of the twist conformer in the trans isomers is mainly determined by the substituent on phosphorus. The size and composition of the transannelated ring are relatively unimportant in this respect. For both cis and trans isomers the preferred geometry is solvent-independent. The measured ^3JPOCH couplings of the cis isomers 3a-10a are used to formulate an expression for the dependence of such couplings upon dihedral angles in bicyclic phosphites.     

31P-NMR-SPEKTROSKOPISCHER NACHWEIS VON SUPERMESITYL-SUBSTITUIERTEM TRIPHOSPHAALLYLLITHIUM UND 2-ARSA-1,3-DIPHOSPHAALLYLLITHIUM

Abstract

The compounds 1.3-bis(2,4,6-tri-tert.butylphenyl)triphosphaallyllithium (5) and 1.3-bis(2,4,6-tritert.butylphenyl)-2-arsa-1,3-diphosphaallyllithium (7) are prepared by deprotonation of a phosphino-substituted diphosphene and arsaphosphene, resp. The presence of trans/trans and cis/trans isomers has been proven by ³¹P-NMR spectroscopy.

Die Verbindungen 1.3-Bis(2,4,6-tri-tert.butylphenyl)triphosphaallyllithium (5) und 1.3-Bis-(2,4,6-tri-tert.butylphenyl)-2-arsa-1,3-diphosphaallyllithium (7) werden durch Deprotonierung eines phosphino-substituierten Diphosphens bzw. Arsaphosphens dargestellt. Das Vorliegen von trans/trans und cis/trans-Isomeren wird durch ³¹P-NMR-Spektroskopie nachgewiesen.     

Synthesis and Study of the Thermal Epimerization of r -2-Ethoxy- cis -4- cis -5-Dimethyl-1,3,2-λ 3 -Dioxaphospholane Using 31 P NMR

The exclusive synthesis of r -2-ethoxy- cis -4- cis -5-dimethyl-1,3,2- u 3 -dioxaphospholane ( cis - 1 ) is reported. The kinetic measurements of the epimerization of cis - 1 to trans - 1 were performed by 31 P NMR from 50 to 80;C in toluene. The energy of activation (E a ) of the epimerization process was calculated from Arrhenius plot. The thermodynamic parameters of the transition state led us to conclude that the activation barrier of the inversion at phosphorus is driven by the enthalpy and by a large and negative entropy of activation.     

Two cobalt coordination polymers with a highly undulated 2-D network and a 2-D (4,4) network

Two cobalt(II) coordination polymers [Co₃(ttmb)₂(H₂O)₆Cl₆] · 3H₂O (1) and Co(ttmb)₂(H₂O)₂](NO₃)₂ · 4H₂O (2) were synthesized by the reaction of 1,3,5-tri(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene (ttmb) and CoCl₂ or Co(NO₃)₂. In 1, each ttmb shows a tri-monodentate coordination mode and bonds three Co(II)s to form a highly undulated 2-D network. The Schläfla symbol for the 2-D network is 3²6². The highly undulated 2-D networks are not catenated, but interdigitate each other. In 2, each ttmb shows a two-monodentate coordination mode and connects two Co(II)s to extend a 2-D (4,4) network. The ttmb exhibits the cis,cis,cis-conformation in 1 and the cis,trans,trans-conformation in 2. The thermal stability of 1 was studied.     

Synthesis of 3-Ethoxy-2-Oxo-3-Phenyl-1,2-Oxaphosphorinane-3,5-Diene

Abstract

In view of the limited number of examples of 2-oxo-l,2-oxaphosphorinane3,5diene derivatives^1,2, we investigated the preparation of the title compound and derivatives of the same. Of additional interest were the spectroscopic propertits of this class of compounds, their stability, and the outcome of their reaction with nucleophilts. Prior work in our laboratory on the synthesis of simple phostones and their derivatives³, led us to use these as starting mataials. The presence of the phenyl substituent in la, (cis and trans isomers) permitted facile introduction of a bromo group through free radical bromination with NBS/AIBN to give 2a,b in 79% overall yield. The individual isomers of 2 were separated; tentative stereochemical assignments were made using NMR spectroscopy. Treatmnt of 2 with LiCl/DMF gave 3; the trans isomer (phenyl and OEt trans) 2b reacted much faster than the cis isomer. Treatmnt of 3 with NBS/AIBN gave 4a,b and 5 which were separated by flash chromatography. Dehydrobromination of 4 (71% yield) was achieved by heating with an excess of Et₃N in toluenc at 95°C to produce 6; likewise, dehydrobromination of 5 at 70°C gave 7.     

Spectrophotometric and Potentiometric Studies on the Binding Abilities of Two Novel Tripodal Imine-Phenol Ligands Towards Al(III) and Ga(III)

The aqueous coordination behavior of two novel tripodal imine-phenol ligands, cis,cis-1,3,5-tris{(2-hydroxybenzilidene)aminomethyl}cyclohexane (TMACHSAL, L¹) and cis,cis-1,3,5-tris{[(2-hydroxyphenyl)ethylidene]aminomethyl}cyclohexane (Me₃- TMACHSAL, L²) with Al³⁺ and Ga³⁺ has been investigated at an ionic strength of 0.1 mol⋅dm⁻³ KCl and 25±1 °C by potentiometric and spectrophotometric methods. Both ligands formed various monomeric metal complex species MLH₃, MLH₂, MLH, ML and MLH₋₁ with Ga(III); and MLH₃, ML and MLH₋₁ with Al(III). The Ga(III) complexes showed higher thermodynamic stability than the Al(III) complexes. Semi-empirical PM6 calculations along with TDDFT/B3LYP/3-21G calculations have been performed to complement the experimental measurements. The calculated structure of the metal complexes predicted a distorted octahedral geometry where favorable ring-flipping from the equatorial conformation in uncomplexed ligands to the axial conformation was observed upon chelation.     

A variable temperature study of the 19-F N.M.R. spectrum of perfluorohexamethyltetrazan: Novel restricted rotation and hindered inversion at the nitrogen atoms [1]

At low temperatures, the ¹⁹F n.m.r. spectrum of the tetrazan (CF₃)₂NN(CF₃)N(CF₃)N(CF₃)₂ shows the presence of two isomers with a free energy difference in stability Δ$\text{G}$ of 2.2 kJ mol^-1. Both isomers show three types of CF₃ group which coalesce at -15°C to three systems of equal intensity (Δ$\text{G}$≠ 52 kJ mol^-1). At 40 °C the two signals assigned to the terminal CF₃ groups coalesce to a single band (Δ$\text{G}$≠ 65 kJ mol^-1).The behaviour is discussed in terms of restricted inversion at the nitrogen atoms, and hindered rotation about the N-N bonds.The hydrazines (CF₃)₂NN(CF₃)NO and (CF₃)₂NN(CF₃)NO₂ have temperature independent spectra.     

Trans-cis isomerization of 4-(2-(9-anthryl)vinyl) pyridine.Molecular structures and ~1H NMR kinetic studies

Both cis- and trans-isomers of 4-(2-(9-anthryl)vinyl)pyridine were isolated and their molecular structures established by X-ray crystallographic method. Variable temperature 1H NMR spectroscopy was used to study the trans to cis isomerization of the title compound. The kinetic study of the reaction was based on the ratio of the NMR integration heights in toluene-d8 of the double doublet due to the cis-isomer at δ 8.51 to that of the multiplet at δ 8. 15 which was kept constant during the whole experiment. The isomerization process was found to be first order and the Arrhenius activation parameters Ea , In A ,△ H≠ and △ S≠ were calculated as 27.84kJ/mol, 6.71, 25.23 kJ/mol and - 197.89 J/(K·mol) , respectively. Besides,conformational analyses of both compounds based on molecular modelling were carried out and the results were used to compare with the experimental data.     

Syntheses of Unique Bicyclophostones and Unexpected Difference in the Reaction of Lawesson's Reagent vs. P2S5 with Cis-Bicyclophostone (1)

Abstract

The purpose of this study was to synthesize trans-l and determine the equilibriurr constant with cis-1. Oniy the synthesis¹ and x-ray structure² of the cis isomer have bcen reported. Four prior synthetic routes to make the vans isomer³ gave only cis product. For example, intrarmolecular ring closure of the cis or trains isomers of 4 (R= (CH₂)₃OH) with LiH or thermal closure of the cis or trans 4 (R= (CH₂)₂) gave only cis-1. Since both iosmers of 1,8-dioxabicyclo[4.4.0] decane are known and readily equilibrate (57% cis and 43% trans), the apparent inaccessibility of trans-1 attracted our attention. Thc preparation of trans-1 was achieved by treatment of cis-1 with Lawesson's reagent (LR) to provide cis-2. followed by oxidation with m-chloroperbenzoic acid/trifluoroacetic acid to give a 5:1 mixture of cis:trans 1, respectively. An unexpected formation of the sulfur analogue of 1 was observed on treatment of cis-1 with P₂S₅/pyridine at reflux temperatures to give a 1.6:1 mixture of cis:trans 3, respectively. Thermal quilibration of 1 at 204°C provided an equilibrium ratio of 99.5% cis and 0.5% of the trans isomer. However, equilibration of 3 at 250°C led to 82.2:17.8 ratio in favor of the cis isomr. These results are consistent with semiemperical MO calculations. The stereochemical outcome on treatment of 4 with LR was also investigated. X-ray structures for six compounds: trans-1, cis-2, cis and trans-3; cis-4 (R=Ph), and cis-5, (R = Ph) wen determined.     

Determination of kinetic triplet of the synthesized Ni3(PO4)2·8H2O by non-isothermal and isothermal kinetic methods

The nickel phosphate octahydrate (Ni₃(PO₄)₂·8H₂O) was synthesized by a simple procedure and characterized by FTIR, TG/DTG/DTA, AAS, and XRD techniques. The morphologies of the title compound and its decomposition product were studied by the SEM method. The dehydration process of the synthesized hydrate occurred in one step over the temperature range of 120–250 °C, and the thermal decomposition product at 800 °C was found to be Ni₃(PO₄)₂. The kinetic parameters (E and A) of this step were calculated using the Ozawa–Flynn–Wall and Kissinger–Akahira–Sunose methods. The iterative methods of both equations were carried out to determine the exact values of E, which confirm the single-step mechanism of the dehydration process. The non-isothermal kinetic method was used to determine the mechanism function of the dehydration, which indicates the contracting disk mechanism of R₁ model as the most probable mechanism function and agrees well with the isothermal data. Besides, the isokinetic temperature value (T _i) was calculated from the spectroscopic data. The thermodynamic functions of the activated complex (ΔS ^≠, ΔH ^≠, and ΔG ^≠) of the dehydration process were calculated using the activated complex theory of Eyring. The kinetic parameters and thermodynamic functions of the activated complex for the dehydration process of Ni₃(PO₄)₂·8H₂O are reported for the first time.     

Synthesis and Biological Activity of Cis 2-(6-Chloropyridine-3-yl)methylamino-4-substitutedphenyl-5,5-dimethyl-1,3,2-dioxaphosphinane 2-Oxides

A series of novel, asymmetric-cyclic phosphoramides containing substituted pyridine were synthesized via the condensation reactions of trans 2-chloro-4-substitutedphenyl-5, 5-dimethyl-1,3,2-dioxaphosphinane 2-oxide with 2-chloro-5-aminomethylpyridine or 3-aminomethylpyridine. The reactions show good stereoselectivity. Only the cis isomer from configuration inversion was obtained, which is the thermodynamic stable product. The structures of the products were characterized by ¹H NMR, ³¹P NMR, IR, MS, and elemental analysis. The configuration of the product was determined by X-ray diffraction analysis. The results of preliminary bioassay showed that the new compounds possess potential insecticidal and fungicidal activities.     

The solid-state isomerization of cis- and trans-(η5-C5H4Me)Mo(CO)2(P(OiPr)3)I

The cis- and trans-(η⁵-C₅H₄Me)Mo(CO)₂(P(OⁱPr)₃)I complexes undergo a bi-directional thermal ligand isomerization reaction to yield an equilibrium mixture of isomers (30/70 cis/trans ratio, 90 °C, < 80 min) in the solid state. The activation energy barrier for the cis-trans isomerization reaction (80–100 °C) was found to be 68 ± 10 kJ mol^–1. In benzene (reflux, 2 h) this isomer ratio was found to be 70:30 cis/trans. DSC and powder XRD studies have revealed reactions that occur in the solid state entailing decomposition and isomerization. DSC experiments did not reveal the presence of the cis–trans isomerization reaction.     

Preparation,spectral characterization,and single crystal X-ray structures of cis and trans isomers of 2,4,6-trifluoroethoxy-1,3,5-triethyl-1,3,5,2λ5, 4λ5, 6λ5-triazatriphosphorinane-2,4,6-trioxide, [ETNP(O)(OCH2CF3)]3

Oxidation of the cis isomer of the λ³-cyclotriphosphazane [EtNP(OCH₂CF₃)]₃ with trimethylamine-N-oxide (TMNO) gives the cis isomer of trioxo-λ⁵-cyclotriphosphazane [EtNP(O)(OCH₂CF₃)]₃; the trans isomer of [EtNP(O)(OCH₂CF₃)]₃ is obtained by the treatment of a cis and trans mixture of [EtNP(OCH₂CF₃)]₃ with aqueous H₂O₂. The two trioxocyclotriphosphazanes have been characterized by elemental analysis, IR, and NMR (¹H, ¹³C, ¹⁹F, and ³¹P) spectroscopy. The solid state structures of both the isomers have been determined by single crystal X-ray diffraction. The six-membered P₃N₃ ring in both the isomers exhibits a twist-boat conformation; in the cis isomer, the trifluoroethoxy substituents lie on the same side of the ring, whereas, in the trans isomer, two trifluoroethoxy groups are on one side of the ring and the third on the other side of the ring. Crystal data for cis-[EtNP(O)(OCH₂CF₃)]₃: monoclinic, P 2₁/ n , a = 13.593(3), b = 9.721(2), c = 17.539(3) Å, β = 99.49(2)°, V = 2286(1) ų, Z = 4, and Final R = 0.047. Crystal data for trans-[EtNP(O)(OCH₂CF₃)]₃: monoclinic, P 2₁/ n , a = 11.685(4), b = 15.115(5), c = 13.233(5) Å, - = 102.21(3)°, V = 2284(1) ų, Z = 4, and Final R = 0.078.     

Kinetics and Mechanism of the Exothermic First-stage Decomposition Reaction for 1,5-Dimethyl-2,6-bis(2,2,2-trinitroethyl)-glycoluril

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The Structure of 2,4-Diorganyl-2,4-Dithioxo-1,3,2λ5,4λ5-Dithiadiphosphetanes in Solution

Abstract

Compounds of the overall composition RPS₂, so called perthiophosphonic acid anhydrides, prefer a dimeric structure in szlution, as it has already been known for the solid compounds. Following compounds [RP(S)S]₂ with R=methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, cyclohexyl, phenyl, 4-methoxy-phenyl and 3,5-dimethyl-piienyl were prepared and characterized by iJJR spectroscopy. The 3,5-ditert-butyl-4-hydroxy-phenyl-compound [1] was also investigated. NHR investigations give evidence for the existence of conligurational isomers of the 2,4-Diorganyl-2,4-dithi-oxo-1,3,2λ⁵,4λ⁵-dithiadiphosphetanes. In solutions an equllibrium between cis and trans isomers is established. The concentration of the two isomers depends on the kind of P and the solvent used. In general the trans isomer has a nigher concentration than the cis isomer. The easy preparation of unsymmetrical compounds by mixing solutions of compounds with different R shows a continous dissociation and association process of the PSPS-ring. This result underlines the existence of a monomeric compound of low concentration as intermediate. An interesting result is obtained for the isopropyl compound. After dissolving e.g. in CDC1₃ almost 90% of the compound is transformed into the other isomer. The progress of the transformation can be followed by NXR spectroscopy. In all other cases the equilibrium state is immediately achieved after preparation of the solution.     

Synthese und Struktur von S{NAs(tBu)2[Os3(CO)11]}2 Das erste Schwefeldiimid mit trans,trans-Konfiguration im Festkörper

Synthesis and Structure of S{NAs(^tBu)₂[Os₃(CO)₁₁]}₂. The First Sulphur Diimide with trans,trans Configuration in the Solid State In the reaction of bis(di-tert-butylarsino) sulphur diimide, S(NAs^tBu₂)₂, with the cluster Os₃(CO)₁₁(NCCH₃) either one or two [Os₃(CO)₁₁] units can be added to the sulphur diimide — according to the molar ratio — yielding Os₃(CO)₁₁As(^tBu)₂NSNAs^tBu₂ ( 1 ) or S{NAs(^tBu)₂[Os₃(CO)₁₁]}₂ ( 2 ), respectively. The title compound μ-[(trans,trans)-bis(di-tert-butyl-arsino)sulphur diimide-As,As]-bis(undecacarbonyl-triangulo-triosmium) ( 2 ) is also obtained upon thermolysis of 1 in refluxing octane; its structure was elucidated by X-ray crystallography. Complex 2 is the first sulphur diimide with a trans,trans configuration in solid state. The trans,trans configuration is forced by the bulky substituents. 2 crystallises with deuterochloroform (1:1) in the monoclinic space group C2/c: a = 25.887(3), b = 8.684(1), c = 26.357(4) Å, β = 103.34(1)°, Z = 4. Due to special positions the SN₂ moiety (inversion center) and the chloroform molecule (twofold axis) are disordered statistically. The S?N bond lengths amount 1.50(2) Å on the average, the angle at, sulphur (111(2)°) is smaller in comparison with open-chained sulphur diimides with the cis, trans and cis,cis configuration. The angles a t the K atoms are enlarged (131(2) and 135(2)°), respectively. With exception of small torsions around the S?N bonds the principle of coplanarity for sulphur diimides is also fulfilled for t,he trans, trans form. The amino residues occupy equatorial positions in the triosmium clusters. I n the triosmium triangle two bonds are almost equal in length (2.891(1) and 2.884(1) Å, respectively), the third Os? Os bond is somewhat enlarged (2.939(1) Å).     

Syntheses of shuttlecock- and bowl-equipped phenylazopyridines and photomodulation of their coordination ability to Zn-porphyrin

Shuttlecock- and bowl-equipped 4-(phenylazo)pyridine derivatives, which bear substituents that allow the pyridine moiety to protrude in the trans form but hinder it in the cis form, have been designed and synthesized. These molecules show cis/trans photoisomerization despite the presence of bulky substituents. ¹H NMR titration with Zn-porphyrin showed that the trans isomers coordinate to Zn-porphyrin much stronger than the cis isomers.     

Cis- und trans-1-Phosphabicyclo[4.4.0]decan

Cis- and trans-1-Phosphabicyclo[4.4.0]decane A mixture of cis-( 5a ) and trans-1-phosphabicyclo [4.4.0] decane 5b has been prepared by free-radical cyclization of (CH₂ = CH? CH₂? CH₂)₂CH? PH₂ 10 . The isomers could be separated in a pure state. Stereostructures have been assigned by ¹³C n.m.r. at 153—302 K. Equilibration of 5a and 5b by u.v. irradiation gave ?G°₃₅ ≈? 0 kJ ° mol^?1 · Activation parameters for ring inversion of “cis” stereoisomer 5a and its “cis” P-sulfid 17a are found to be ΔG° = 41.9 kJ · mol^?1 and 39.7 kJ · mol^?1, respectively. Treatment of 5a and 5b with H₂O₂, sulfur, selenium, HSO₃F, CH₃I, CS₂, and Ni(CO)₄, respectively, yield the corresponding derivatives. ¹H, ¹³C, ³¹P, ⁷⁷Se n.m.r. and i.r. data are reported.     

Donor-Acceptor Complexes in Copolymerization. XXXV. Alternating Diene-Dienophile Copolymers. 3. Copolymerization of cis- and trans-1, 3-Pentadiene with Maleic Anhydride and Acrylonitrile… AlEt1.5CI1.5

Abstract

The copolymerization of the cis or trans isomers of 1,3-pentadiene with maleic anhydride in the presence of a peroxide catalyst yields identical equimolar, alternating copolymers in which the pentadiene units have a cis-1, 4 configuration (IR, NMR). The copolymerization of the cis or trans isomers of 1, 3-pentadiene with acrylonitrile in the presence of ethyl aluminum sesquichloride yields identical equimolar, alternating copolymers in which the pentadiene units have a trans-1,4 configuration (IR, NMR). Although the trans isomer forms cyclic adducts with both maleic anhydride and acrylonitrile, the cis isomer does not undergo the Diels-Alder reaction with these dienophlles. The formation of identical copolymers from cis- and trans-1, 3-pentadiene is attributed to isomerization of the diene-dienophile charge transfer complex in the excited state, resulting in the generation of the same homopolymerizable exciplex from both isomers.     

Kinetic and thermodynamic analysis of degradation of doripenem in the solid state

The kinetic and thermodynamic parameters of degradation of doripenem were studied using a high‐performance liquid chromatography method. In dry air, the degradation of doripenem was a first‐order reaction depending on the substrate concentration. At increased relative air humidity, doripenem was degraded according to the autocatalysis kinetic model. The dependence ln k = f1/T) was described by the equations ln k = 5.10 ± 13.06 ? (7576 ± 4939)(1/T) in dry air and ln k = 46.70 ± 22.44 ? (19,959 ± 8031)(1/T) at 76.4% relative humidity (RH). The thermodynamic parameters E_a, ΔH^≠a, and ΔS^≠a of the degradation of doripenem were calculated. The dependence ln k = f (RH%) was described by the equation ln k = (0.155 ± 0.077) × 10^?1 (RH%) ? (3.45 ± 21.8) × 10^?10. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 722–728, 2012