Synthesis and Conformation of Fluorinated β‐Peptidic Compounds

Experimental and theoretical data indicate that, for α‐fluoroamides, the F? C? C(O)? N(H) moiety adopts an antiperiplanar conformation. In addition, a gauche conformation is favoured between the vicinal C? F and C? N(CO) bonds in N‐β‐fluoroethylamides. This study details the synthesis of a series of fluorinated β‐peptides ( 1 – 8 ) designed to use these stereoelectronic effects to control the conformation of β‐peptide bonds. X‐ray crystal structures of these compounds revealed the expected conformations: with fluorine β to a nitrogen adopting a gauche conformation, and fluorine α to a C?O group adopting an antiperiplanar conformation. Thus, the strategic placement of fluorine can control the conformation of a β‐peptide bond, with the possibility of directing the secondary structures of β‐peptides.     

Determination of the Influence of Side‐Chain Conformation on Glycosylation Selectivity using Conformationally Restricted Donors

The synthesis of a series of conformationally locked mannopyranosyl thioglycosides in which the C6?O6 bond adopts either the gauche,gauche, gauche,trans, or trans,gauche conformation is described, and their influence on glycosylation stereoselectivity investigated. Two 4,6‐O‐benzylidene‐protected mannosyl thioglycosides carrying axial or equatorial methyl groups at the 6‐position were also synthesized and the selectivity of their glycosylation reactions studied to enable a distinction to be made between steric and stereoelectronic effects. The presence of an axial methoxy group at C6 in the bicyclic donor results in a decreased preference for formation of the β‐mannoside, whereas an axial methyl group has little effect on selectivity. The result is rationalized in terms of through‐space stabilization of a transient intermediate oxocarbenium ion by the axial methoxy group resulting in a higher degree of S_N1‐like character in the glycosylation reaction. Comparisons are made with literature examples and exceptions are discussed in terms of pervading steric effects layered on top of the basic stereoelectronic effect.     

3‐Fluoro‐N‐methyl‐D‐aspartic acid (3F‐NMDA) Stereoisomers as Conformational Probes for Exploring Agonist Binding at NMDA Receptors

N‐Methyl‐D ‐aspartate (NMDA) is the prototypical agonist of the NMDA receptor subtype of ionotropic glutamate receptors. Stereogenic placement of a C? F bond at the 3‐position of (S)‐NMDA generates either the (2S,3S)‐ or (2S,3R)‐ diastereoisomers of 3F‐NMDA. The individual diastereoisomers were prepared by synthesis in enantiomerically pure forms and it was found that (2S,3S)‐3F‐NMDA is an agonist with a comparable potency to NMDA itself, whereas the (2S,3R)‐diastereoisomer has negligible potency. The difference in potency of these stereoisomers is attributed to a preference of the C? F bond (2S,3S)‐3F‐NMDA to adopt a gauche conformation to the C? N⁺ bond in the binding conformation, whereas the (2S,3R)‐3F‐NMDA forces these bonds anti, losing electrostatic stabilisation, to achieve the required binding conformation. These observations illustrate the utility of stereoselective fluorination in influencing the molecular conformation of β‐fluorinated amino acids and thus probing the active conformations of bioactive compounds at receptors.     

After the electronic field: Structure,bonding, and the first hyperpolarizability of HArF

In this work, we add different strength of external electric field (E_ext) along molecule axis (Z‐axis) to investigate the electric field induced effect on HArF structure. The H‐Ar bond is the shortest at E_ext = ?189 × 10^?4 and the Ar‐F bond show shortest value at E_ext = 185 × 10^?4 au. Furthermore, the wiberg bond index analyses show that with the variation of HArF structure, the covalent bond H‐Ar shows downtrend (ranging from0.79 to 0.69) and ionic bond Ar‐F shows uptrend (ranging from 0.04 to 0.17). Interestingly, the natural bond orbital analyses show that the charges of F atom range from ?0.961 to ?0.771 and the charges of H atoms range from 0.402 to 0.246. Due to weakened charge transfer, the first hyperpolarizability (β_tot) can be modulated from 4078 to 1087 au. On the other hand, make our results more useful to experimentalists, the frequency‐dependent first hyperpolarizabilities were investigated by the coupled perturbed Hartree‐Fork method. We hope that this work may offer a new idea for application of noble‐gas hydrides. © 2013 Wiley Periodicals, Inc.     

tert‐Butyl N‐{2‐[N‐(N,N′‐dicyclohexyl­ureido­carbonyl­ethyl)­carbamoyl]prop‐2‐yl}carbamate

The title compound, C₂₅H₄₄N₄O₅, exhibits a turn with the main chain reversing direction, held together by an intramol­ecular N—H?O hydrogen bond. In the urea fragment, a notable amide C—N bond between the carboxyl C and the tertiary N atom shows marked single‐bond character [1.437 (2) Å]. The dihedral angle of the β‐alanyl residue, centrally located in the turn, is gauche [69.2 (2)°]. The packing is mediated by two intermolecular hydrogen bonds and van der Waals contacts involving the methyl moieties and the cyclo­hexyl rings.     

Methyl 4‐O‐β‐D‐mannopyranosyl β‐D‐xylopyranoside

Methyl β‐D‐mannopyranosyl‐(1→4)‐β‐D‐xylopyranoside, C₁₂H₂₂O₁₀, (I), crystallizes as colorless needles from water, with two crystallographically independent molecules, (IA) and (IB), comprising the asymmetric unit. The internal glycosidic linkage conformation in molecule (IA) is characterized by a ϕ′ torsion angle (O5′_Man—C1′_Man—O1′_Man—C4_Xyl; Man is mannose and Xyl is xylose) of −88.38 (17)° and a ψ′ torsion angle (C1′_Man—O1′_Man—C4_Xyl—C5_Xyl) of −149.22 (15)°, whereas the corresponding torsion angles in molecule (IB) are −89.82 (17) and −159.98 (14)°, respectively. Ring atom numbering conforms to the convention in which C1 denotes the anomeric C atom, and C5 and C6 denote the hydroxymethyl (–CH₂OH) C atom in the β‐Xylp and β‐Manp residues, respectively. By comparison, the internal glycosidic linkage in the major disorder component of the structurally related disaccharide, methyl β‐D‐galactopyranosyl‐(1→4)‐β‐D‐xylopyranoside), (II) [Zhang, Oliver & Serriani (2012). Acta Cryst. C 68 , o7–o11], is characterized by ϕ′ = −85.7 (6)° and ψ′ = −141.6 (8)°. Inter‐residue hydrogen bonding is observed between atoms O3_Xyl and O5′_Man in both (IA) and (IB) [O3_Xyl...O5′_Man internuclear distances = 2.7268 (16) and 2.6920 (17) Å, respectively], analogous to the inter‐residue hydrogen bond detected between atoms O3_Xyl and O5′_Gal in (II). Exocyclic hydroxymethyl group conformation in the β‐Manp residue of (IA) is gauche–gauche, whereas that in the β‐Manp residue of (IB) is gauche–trans.     

1,7‐Dideaza‐2′‐deoxy‐6‐nitronebularine: a pyrrolo[2,3‐b]pyridine nucleoside with an intramolecular hydrogen bond stabilizing the syn conformation

The title compound [systematic name: 1‐(2‐deoxy‐β‐D‐erythro‐pentofuranosyl)‐4‐nitro‐1H‐pyrrolo[2,3‐b]pyridine], C₁₂H₁₃N₃O₅, forms an intramolecular hydrogen bond between the pyridine N atom as acceptor and the 5′‐hydroxy group of the sugar residue as donor. Consequently, the N‐glycosylic bond exhibits a syn conformation, with a χ torsion angle of 61.6 (2)°, and the pentofuranosyl residue adopts a C2′‐endo envelope conformation (²E, S‐type), with P = 162.1 (1)° and τ_m = 36.2 (1)°. The orientation of the exocyclic C4′—C5′ bond is +sc (gauche, gauche), with a torsion angle γ = 49.1 (2)°. The title nucleoside forms an ordered and stacked three‐dimensional network. The pyrrole ring of one layer faces the pyridine ring of an adjacent layer. Additionally, intermolecular O—H...O and C—H...O hydrogen bonds stabilize the crystal structure.     

Enantioselective Aziridination of Cyclic Enals Facilitated by the Fluorine‐Iminium Ion Gauche Effect

The enantioselective, organocatalytic aziridination of small, medium and macro‐cyclic enals is reported using (S)‐2‐(fluorodiphenyl methyl)‐pyrrolidine. Central to the reaction design is the reversible formation of a β‐fluoroiminium ion intermediate, which is pre‐organised on account of the fluorine‐iminium ion gauche effect. This conformational effect positions the fluorine substituent synclinal‐endo to the electropositive nitrogen centre thus benefiting from favourable stereoelectronic and electrostatic interactions (σ_C?H→σ_C?F*; F^δ?…?N⁺). Consequently, one of the shielding groups on the fluorine‐bearing carbon atom is positioned above the π‐system, forming the basis of an enantioinduction strategy. Treatment of this intermediate with a “nitrene” source furnished a series of novel, optically active aziridines (e.r. up to 99.5:0.5). Further derivatisation of the product aziridines gives facile access to various amino acid derivatives, including β‐fluoroamino acids. Crystallographic analyses of both the aziridines and their derivatives are disclosed.     

Structures and properties of π Br‐bond in complexes C2H4−nFn?BrF (n = 0–2)

Using the counterpoise‐corrected potential energy surface method, the stationary structures of the π Br‐bond complexes C₂H_4‐nF_n? BrF (n = 0–2) with all real frequencies have been obtained at MP2/aug‐cc‐pVDZ level. The order of the π Br‐bond length is 2.625 Å (C₂H₄? BrF) < 2.714 Å (C₂H₃F? BrF) < 2.751 Å (g‐C₂H₂F₂? BrF) < 2.771 Å (trans‐C₂H₂F₂? BrF) < 2.778 Å (cis‐C₂H₂F₂? BrF). The interaction energies (E_int) are, respectively,‐5.9 (C₂H₄? BrF),‐4.4 (C₂H₃F? BrF),‐3.7 (g‐C₂H₂F₂? BrF),‐3.1 (cis‐C₂H₂F₂? BrF),‐2.8 kcal/mol (trans‐C₂H₂F₂? BrF), at the CCSD (T)/aug‐cc‐pVDZ level, which include larger electron correlation contributions (E_corre). The order of E_corre is‐3.40 (C₂H₄? BrF),‐3.60 (C₂H₃F? BrF),‐3.85 (g‐C₂H₂F₂? BrF),‐3.86 (cis‐C₂H₂F₂? BrF),‐3.88 kcal/mol (trans‐C₂H₂F₂? BrF). The earlier results show above that the F substituent effect elongates the π Br‐bond, reduces the E_int, and increases the E_corre contribution of the interaction energy. Interestingly, the interaction energy of the cis‐C₂H₂F₂? BrF structure with longer interaction distance is larger than that of the corresponding trans‐C₂H₂F₂? BrF structure with shorter interaction distance. This reason comes from a special secondary interaction between lone pairs of Br atom with positive charge and some atoms (H, C) with positive charges of C₂H₂F₂ in the cis‐C₂H₂F₂? BrF structure. Comparing with corresponding C₂H_4‐nF_n? ClF and C₂H_4‐nF_n? HF, the C₂H_4‐nF_n? BrF system has the larger E_int in which main contribution comes from the larger E_corre, representing the larger dispersion interaction. The larger E_corre contribution of the E_int of π Br‐bond can be used to understand that the π Br‐bond is shorter and stronger than corresponding π Cl‐bond. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

p‐Cresyl 2,3‐an­hydro‐5‐deoxy‐5‐phthal­imido‐1‐thio‐α‐d‐lyxo­furan­oside

The crystal structure of the title compound, C₂₀H₁₇NO₄S, (I), was determined in order to compare the solution and solid‐state conformations. The mol­ecule was synthesized as a building block for incorporation into oligosaccharides comprised of conformationally restricted furan­ose residues. The furan­ose ring adopts an envelope conformation with the ring O atom displaced above the plane (an ^OE conformation). The pseudorotational phase angle (P) is 88.6° and the puckering amplitude (τ_m) is 31.5°. The C₂—C₁—S—C(Ph) torsion angle is ?163.2 (2)°, which places the aglycone in the exo‐anomeric effect preferred position. The C1—S—C14 bond angle is 99.02 (13)° and the plane of the cresyl moiety is oriented nearly parallel to the four in‐plane atoms of the furan­ose ring envelope. The orientation about the C4—C5 bond is gauche–gauche [Bock & Duus (1994). J. Carbohydr. Chem. 13 , 513–543].     

Crystal structure of a liquid crystal non‐symmetric dimer: cholesteryl 4‐[4‐(4‐n‐butylphenylethynyl)phenoxy]butanoate

The crystal structure of cholesteryl 4‐[4‐(4‐n‐butylphenylethynyl)phenoxy]butanoate [phase sequence: Cr 155°C (46.1?J?g^?1) SmA 186.8°C (1.5?J?g^?1) TGB‐N* 204.7 (6?J?g^?1) I] has been solved from single crystal X‐ray diffraction data. The compound crystallizes in the monoclinic space group P2₁ with unit cell parameters: a?=?13.129(2), b?=?9.3904(10), c?=?17.4121(8)?Å, β?=?92.790(7)°, Z?=?2. The structure has been solved by direct methods and refined to R?=?0.0606 for 3?250 observed reflections. The bond distances and angles are in good agreement with the corresponding values for compounds containing phenyl and cholesterol moieties. The phenyl rings A and B are planar. The dihedral angle between the least‐squares planes of the two phenyl rings is 28°. The cholesterol moiety has the usual structure: the C and E rings have chair conformations, and the D and F rings adopt half‐chair conformations. The molecules in the unit cell are arranged in an antiparallel manner. The crystal structure is stabilized by an intermolecular C–H…O contact of 2.989(10)?Å.     

A toyocamycin analogue with the sugar moiety in a syn conformation

The title compound [systematic name: 4‐amino‐5‐cyano‐1‐(β‐d ‐ribofuranosyl)‐7H‐pyrrolo[2,3‐d]pyrimidine hemihydrate], C₁₂H₁₃N₅O₄·0.5H₂O, is a regioisomer of toyocamycin with the ribofuranosyl residue attached to the pyrimidine moiety of the heterocycle. This analogue exhibits a syn glycosylic bond conformation with a χ torsion angle of 57.51 (17)°. The ribofuranose moiety shows an envelope C2′‐endo (²E) sugar conformation (S‐type), with P = 161.6 (2)° and τ_m = 41.3 (1)°. The conformation at the exocyclic C4′—C5′ bond is +sc (gauche, gauche), with a γ torsion angle of 54.4 (2)°. The crystal packing is stabilized by intermolecular O—H...O, N—H...N and O—H...N hydrogen bonds; water molecules, located on crystallographic twofold axes, participate in interactions. An intramolecular O—H...N hydrogen bond stabilizes the syn conformation of the nucleoside.     

1,2‐Bis(trifluoromethyl)ethene‐1,2‐dicarbonitrile: (2+2) Cycloadditions with Vinyl Ethers

The title compound (short version: BTE) occurs in (E)‐ and (Z)‐isomers (both with b.p. of ca. 100°) which equilibrate with nucleophilic catalysts. Both undergo (2+2) cycloadditions with methyl vinyl ether at 25°. Three stereogenic centers in the cyclobutanes led to four rac‐diastereoisomers, which were obtained in pure and crystalline state. The structures were elucidated by ¹⁹F‐NMR spectroscopy and confirmed by two X‐ray analyses. The cycloadditions were not stereospecific: e.g., (E)‐BTE furnished 73% trans‐adducts (with respect to the CF₃ groups) and 27% cis‐adducts. The loss of stereochemical integrity occurs in the intermediate gauche‐zwitterions which can cyclize or rotate, but not dissociate. Under extreme conditions (2M LiClO₄ in Et₂O, 70°, 3 months), the thermodynamic equilibrium of the four cyclobutanes was achieved. Considerations of Coulombic attraction and conformational strain in the zwitterionic intermediates allow us to rationalize the observed proportions of diastereoisomeric cyclobutanes. Ethyl vinyl ether and butyl vinyl ether furnished cyclobutanes in similar diastereoisomer ratios.     

Orientational Preference of Long,Multicenter Bonds in Radical Anion Dimers: A Case Study of π‐[TCNB]22− and π‐[TCNP]22−

The similar shape and electronic structure of the radical anions of 1,2,4,5‐tetracyanopyrazine (TCNP) and 1,2,4,5‐tetracyanobenzene (TCNB) suggest a similar relative orientation for their long, multicenter carbon?carbon bond in π‐[TCNP]₂^2? and in π‐[TCNB]₂^2?, in good accord with the Maximin Principle predictions. Instead, the two known structures of π‐[TCNP]₂^2? have a D_2h(θ=0°) and a C₂(θ=30°) orientation (θ being the dihedral angle that determines the rotation of one radical anion relative to the other along the axis that passes through center of the two six‐membered rings). The only known π‐[TCNB]₂^2? structure has a C₂(θ=60°) orientation. The origin of these preferences was investigated for both dimers by computing (at the RASPT2/RASSCF(30,28) level) the variation with θ of the interaction energy (E_int) and the variation of the E_int components. It was found that: 1) a long, multicenter bond exists for all orientations; 2) the E_int(θ) angular dependence is similar in both dimers; 3) for all orientations the electrostatic component dominates the value of E_int(θ), although the dispersion and bonding components also play a relevant role; and 4) the Maximin Principle curve reproduces well the shape of the E_int(θ) curve for isolated dimers, although none of them reproduce the experimental preferences. Only after the (radical anion)^.? ??? cation⁺ interactions are also included in the model aggregate are the experimental data reproduced computationally.     

Activation of Strong Boron–Fluorine and Silicon–Fluorine σ‐Bonds: Theoretical Understanding and Prediction

The oxidative addition of BF₃ to a platinum(0) bis(phosphine) complex [Pt(PMe₃)₂] ( 1 ) was investigated by density functional calculations. Both the cis and trans pathways for the oxidative addition of BF₃ to 1 are endergonic (ΔG°=26.8 and 35.7 kcal mol^?1, respectively) and require large Gibbs activation energies (ΔG°^≠=56.3 and 38.9 kcal mol^?1, respectively). A second borane plays crucial roles in accelerating the activation; the trans oxidative addition of BF₃ to 1 in the presence of a second BF₃ molecule occurs with ΔG°^≠ and ΔG° values of 10.1 and ?4.7 kcal mol^?1, respectively. ΔG°^≠ becomes very small and ΔG° becomes negative. A charge transfer (CT), F→BF₃, occurs from the dissociating fluoride to the second non‐coordinated BF₃. This CT interaction stabilizes both the transition state and the product. The B?F σ‐bond cleavage of BF₂Ar^F (Ar^F=3,5‐bis(trifluoromethyl)phenyl) and the B?Cl σ‐bond cleavage of BCl₃ by 1 are accelerated by the participation of the second borane. The calculations predict that trans oxidative addition of SiF₄ to 1 easily occurs in the presence of a second SiF₄ molecule via the formation of a hypervalent Si species.     

7‐Deaza‐2,8‐diaza­adenosine

In the title compound [systematic name: 4‐amino‐7‐(β‐d ‐ribofuranos­yl)‐7H‐pyrazolo[3,4‐d][1,2,3]triazine], C₉H₁₂N₆O₄, the torsion angle of the N‐glycosylic bond is high anti [χ = −83.2 (3)°]. The ribofuran­ose moiety adopts the C2′‐endo–C1′‐exo (²T₁) sugar conformation (S‐type sugar pucker), with P = 152.4° and τ_m = 35.0°. The conformation at the C4′—C5′ bond is +sc (gauche,gauche), with the torsion angle γ = 52.0 (3)°. The compound forms a three‐dimensional network that is stabilized by several hydrogen bonds (N—H⋯O, O—H⋯N and O—H⋯O).     

Synthesis and Characterization of Two Formyl 2‐Tetrazenes

The synthesis of two formyl 2‐tetrazenes, namely, (E)‐1‐formyl‐1,4,4‐trimethyl‐2‐tetrazene ( 2 ) and (E)‐1,4‐diformyl‐1,4‐dimethyl‐2‐tetrazene ( 3 ), by oxidation of (E)‐1,1,4,4‐tetramethyl‐2‐tetrazene ( 1 ) using potassium permanganate in acetone solution is presented. Compound 3 was also synthesized in an improved yield from the oxidation of 1‐formyl‐1‐methylhydrazine ( 4a ) using potassium permanganate in acetone. Both compounds 2 and 3 were characterized by analytical (elemental analysis, GC‐MS) and spectroscopic methods (¹H, ¹³C, and ¹⁵N NMR spectroscopy, and IR and Raman spectroscopy). In addition, the solid‐state structures of the compounds were confirmed by low‐temperature X‐ray analysis. (Compound 2 : triclinic; space group P‐1; a=5.997(1) Å, b=8.714(1) Å, c=13.830(2) Å; α=107.35(1)°, β=90.53(1)°, γ=103.33(1)°; V_UC=668.9(2) ų; Z=4; ρ_calc=1.292 cm^?3. Compound 3 : monoclinic; space group P2₁/c; a=5.840(2) Å, b=7.414(3) Å, c=8.061(2) Å; β=100.75(3)°; V_UC=342(2) ų; Z=2; ρ_calc=1.396 g cm^?3.) The vibrational frequencies of compounds 2 and 3 were calculated using the B3LYP method with a 6‐311+G(d,p) basis set. We also computed the natural bond orbital (NBO) charges using the rMP2/aug‐cc‐pVDZ method and the heats of formation were determined on the basis of their electronic energies. Furthermore, the thermal stabilities of these compounds, as well as their sensitivity towards classical stimuli, were also assessed by differential scanning calorimetry and standard BAM tests, respectively. Lastly, the attempted synthesis of (E)‐1,2,3,4‐tetraformyl‐2‐tetrazene ( 6 ) is also discussed.     

2′‐Deoxy‐5‐propynyluridine: a nucleoside with two conformations in the asymmetric unit

The title compound, 1‐(2‐deoxy‐β‐d ‐erythro‐pentofuranosyl)‐5‐(prop‐1‐ynyl)pyrimidin‐2,4(1H,3H)‐dione, C₁₂H₁₄N₂O₅, shows two conformations in the crystalline state: conformer 1 adopts a C2′‐endo (close to ²E; S‐type) sugar pucker and an anti nucleobase orientation [χ = −134.04 (19)°], while conformer 2 shows an S sugar pucker (twisted C2′‐endo–C3′‐exo), which is accompanied by a different anti base orientation [χ = −162.79 (17)°]. Both molecules show a +sc (gauche, gauche) conformation at the exocyclic C4′—C5′ bond and a coplanar orientation of the propynyl group with respect to the pyrimidine ring. The extended structure is a three‐dimensional hydrogen‐bond network involving intermolecular N—H...O and O—H...O hydrogen bonds. Only O atoms function as H‐atom acceptor sites.     

Random-Coil configurations of the polymormals [CH2?O?(CH2)y?O?]. II. Dipole moments of poly(1,3–dioxepane) [CH2?O?(CH2)4?O?;]

Dielectric constant measurements were carried out on a sample of poly(1,3–dioxepane) [CH₂? O? (CH₂)₄? O? ], in benzene over the range 25—60°C. This chain molecule was found to be very similar to poly(1,3–dioxolane) [CH₂? O? (CH₂)₂? O? ] in having a relatively small dipole moment, which increases markedly with increasing temperature. Rotational isomeric-state calculations show that these two characteristics are due to very strong preferences for gauche states in the two central bonds in the sequence CH₂? O? CH₂? O? CH₂. Such pairs of gauche states, necessarily of the same sign, place neighboring-group dipoles in essentially antiparallel orientations. The resulting attenuation of dipole vectors is the origin of the small dipole moment, and the disruption of these preferred conformations with increasing temperature gives rise to the large positive temperature coefficient of the dipole moment.     

环丙沙星-钨硅多金属氧酸盐的制备及热分解动力学

A new polyoxometalate （CPFX·HCl）3H4SiW12O40·10H2O was prepared from ciprofloxacin hydrochloride and H4SiW12O40·nH2O in aqueous solution, and characterized by elemental analysis, IR spectra and DTA-TG-DTG techniques. The IR spectrum confirmed the presence of Keggin structure and the characteristic functional group for ciprofloxacin in the compound. The TG-DTA-DTG curves showed that its thermal decomposition was a four-step process consisting of simultaneous collapse of Keggin type structure. The residue of decomposition was the mixture of WO3 and SiO2, confirmed by X-ray diffraction and IR spectroscopy. The decomposition mechanism and nonisothermal kinetic parameters of the polyoxometalate were obtained from an analysis to the TG-DTG curves by the single scanning methods （the Achar method and Coats-Redfern method） and the multiple scanning methods （the Kissinger method, Flynn-Wall-Ozawa method and Starink method）. The results indicate that the kinetic equationswith parameters describing the thermal decomposition reaction are dα/dt=6.65×10^6[3（1-α）^2/3]e^-10495.5/T with E=87.26 kJ/mol and A=6.65×10^6 s^-1 for the second step,dα/dt=7.01×10^9（1-α）e^-18770.7/T with E=156.06 kJ/mol and A=7.01×10^9 s^-1 for the third step,dα/dt=9.77×10^43[（1-α）^2]e^-88980.0/T with E=739.78 kJ/mol and A=9.77×10^43 s^-1 for the fourth step.