Synthesis and Structure of A Novel Caged Bicyclic Phosphate Flame Retardant

PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) and phosphorus oxychloride in this paper. Its structure was characterized by elemental analysis. FTIR, H-1 NMR. P-31 NMR and X-ray diffraction analysis.

Evolution and organic geochemical significance of bicyclic sesquiterpanes in pyrolysis simulation experiments on immature organic-rich mudstone

Sesquiterpanes are ubiquitous components of crude oils and ancient sediments.Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hesigewula Sag were analyzed by gas chromatography-mass spectrometry(GC-MS).C14 bicyclic sesquiterpanes,namely,8β(H)-drimane,8β(H)-homodrimane,and 8 a(H)-homodrimane were detected and identified on basis of their diagnostic fragment ions(m/z123,179,193,and 207),and previously published mass spectra data,and these bicyclic sesquiterpanes presented relatively regular characteristics in their thermal evolution.The ratios 8β(H)-drimane/8β(H)-homodrimane,8β(H)-homodrimane/8 a(H)-homodrimane,and 8β(H)-drimane/8 a(H)-homodrimane all show a clear upward trend with increasing temperature below the temperature turning point.Thus,all these ratios can be used as evolution indexes of source rocks in the immature-lowmaturity stage.However,the last two ratios may be more suitable than the first ratio as valid parameters for measuring the extent of thermal evolution of organic matter in the immature-low-maturity stage because their change amplitude with increasing temperature is more obvious.

The atom-bond connectivity index of chemical bicyclic graphs

The atom-bond connectivity（ABC） index provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes,which is defined as ABC（G） =∑ uv∈E（G） √d u＋dv-2 dudv,where du denotes the degree of a vertex u in G.A chemical graph is a graph in which no vertex has degree greater than 4.In this paper,we obtain the sharp upper and lower bounds on ABC index of chemical bicyclic graphs.

Theoretical Studies on the Thermodynamic Properties and Detonation Performances of Bicyclic Nitramines:TNAD Isomers

Ab initio molecular orbital calculations have been performed at Hartree-Fock （HF）, second-order Mrller-Plesset （MP2）, and hybrid density functional theory （DFT） B3LYP levels with 6-31G^＊＊ basis set to investigate the low sensitive explosive trans-1,4,5,8-tetranitro-1,4,5,8- tetraazadecalin （TNAD） and its seven bicyclic isomers. Their molecular geometries, electronic structures, thermodynamic properties, and detonation performances were predicted and compared. The relationships between structures and various properties were discussed in detail. The calculated results agree well with the available experimental data, and suggest that some compounds may be novel potential candidates of high energy density materials （HEDMs） with performances better than TNT （2,4,6-trinitrotoluene） and similar to RDX （1,3,5-trinitro-1,3,5-triazacyclohexane）.

Synthesis of Caged Bicyclic Phosphate Derivatives

Seven caged bicyclic phosphate compounds were synthesized by using 1-oxo-4-hydroxymethyl-2, 6, 7-trioxa-l-pho-sphabicyclo [ 2.2.2 ] octane （PEPA） as starting material. Within them were three PEPA derivatives containing single caged bicyclic phosphate structure（ 1a, 2a, 3a）, another three PEPA deviratives containing two caged bicyclic phosphate structures（1b, 2b, 3b） and one devirative（1c） containing three caged bicyclic phosphate structures. Structures of the products were characterized by FTIR, ^1H NMR, elemental analysis and TG analysis. The reaction conditions were also discussed. Thermal analysis showed they had high thermal stability and excellent char-forming ability. Besides, these compounds had pentaerythritol bone and flame retardant dements of phosphorus, bromine or nitrogen simultaneously in their molecules, endowed them with good fire retardancy, and made them can be used as intumescent flame retardant.

Three Novel Bicyclic Taxoids from the Needles of the Chinensis yew, Taxus chinensis var mairei

Three novel bicyclic taxane diterpenoids with the rare 6/12-membered rings wereisolated from the need ies of Taxus chinensis var. mairei. The structures were established with the help of 1D and 2D NMR spectral analysis.

Source diagnostic and weathering indicators of oil spills utilizing bicyclic sesquiterpanes

Bicyclic Sesquiterpanes （BSs） are ubiquitous components of crude oils and ancient sediments. BSs in crude oils and diesel oil were identified and characterized, the effects of moderate weathering on BS distributions were discussed, and a methodology using diagnostic indices of BSs was developed for oil correlation and dif- ferentiation. The results showed that crude oils and oil products had different abundances and distributions of BSs and, consequently, resulted in different diagnostic ratios. The selected diagnostic ratio indices of BSs, such as BS4/BS5 （ratio of 4,4,8,9,9-pentamethyl-decahydronaphthalene to 8/3 （H）-drimane）, BS6/BS5 （ratio of 4,4,9,9,10-pentamethyl-decahydronaphthalene to 8/3 （H）-drimane）, BS8/BS9 （ratio of the second peak to the third peak of C16 sequiterpane）, and BS8/BSIO （ratio of C16 sequiterpane to 8fl （H）-homodrimane）, still maintained better stabilities （%RSD 〈 5%） after weathering for 30 d. The longer weathering process （150 d） had some effect on such ratios （5% 〈 %RSD 〈 10%）. The facts of the uniqueness, abundance in petroleum, and chemical stability of BSs enable them to be suitable as an effective diagnostic means for identifying spilled oil with moderate weathering, particularly for lighter refined product samples that are difficult to identify by current techniques.

PROMOTION EFFECT OF MELAMINE ON FLAME RETARDANCY OF EPOXY RESINS CONTAINING CAGED BICYCLIC PHOSPHATE

Caged bicyclic phosphate （CBP） and its dimelamine salt （PDS） were synthesized and added to epoxy resins to obtain the flame retarded epoxy resin composites. The flammability of the composites was characterized by the limiting oxygen index （LOI） and cone calorimeter tests. The LOI values of flame retarded composites increase consistently with the increase of flame retardant amounts, and they are almost the same when the loading of CBP is the same as that of PDS, although the phosphorus content of PDS is much lower than that of CBP. The total heat release increases in the order of CBP30/ER 〈 PDS30/ER 〈 PDS15/ER 〈 CBPI5/ER, whereas that of specific extinction area is CBP15/ER 〉 CBP30/ER 〉 PDS30/ER ≌ PDS15/ER. PDS exhibits more effective inhibition of oxidation of combustible gases. In the tests of thermogravimetric analyses （TG） and Fourier transform infrared spectroscopy （FT-IR）, it is found that the degradation of the composites is influenced greatly by the addition of flame retardants. By scanning electron microscopy （SEM）, a thick and tight char-layer is observed for PDS30/ER, resulting from the interaction of nitrogen species with phosphorus species. Therefore, the combination of CBP with melamine in the flame retarded system can improve the flame retardancy greatly.

Study of Flame Retardation of Polycarbonate Modified by Polyhedral Oligomeric Silsesquioxane and Caged Bicyclic Phosphate

The flame-retarded polycarbonate（PC） has been made with octaphenyl polyhedral silsesquioxane（OPS） and/or caged bicyclic phosphate（Trimer）.Thermal gravimetric analysis（TGA）,Fourier-transform infrared（FTIR）,TGA-FTIR,limiting oxygen index（LOI）,and mechanical tests have been employed to characterize the modified PC.The additives of OPS and Trimer in PC have been proved to be effective flame-retardants because of the synergistic interaction between the elements of P and Si.The role of OPS and Trimer in PC degradation are different：OPS participates in the charring of PC,while Trimer makes PC degrade in advance.In addition,OPS and Trimer induced obvious differences in the mechanical properties of PC.

Chemoenzymatic Synthesis of an Enantiomerically Enriched Bicyclic Carbocycle Using <i>Candida parapsilosis</i>ATCC 7330 Mediated Enantioselective Hydrolysis

Enantiomerically enriched (R)-1-(2-bromocycloalkenyl)-3-buten-1-ol and its derivatives were obtained via enantioselective hydrolysis [resolution] with good enantioselectivities (E = 31 to >500) using Candida parapsilosis ATCC 7330. The various reaction parameters were optimized for enantioselective hydrolysis to achieve high enantiomeric excess (ee) and conversions. Among the substrates tested, (RS)-1-(2-bromocyclohex-1-en-1-yl) but-3-yn-1-yl acetate was hydrolysed by the biocatalyst in 12 h to the corresponding (R)-alcohol in 49% conversion and >99 ee. The optically pure allylic alcohol thus obtained was used as a chiral starting material for the synthesis of an enantiomerically enriched bicyclic alcohol effectively establishing achemoenzymatic route.

Facile Synthesis of Novel Chiral Bicyclic Thioureas and Their Crystal Structures

The novel well-defined chiral bicyclic thioureas based on enantiopure unsymmetric cis-2,5-disustituted pyrrolidine skeleton were firstly synthesized and fully characterized by their 1H NMR, 13C NMR and HRMS. Their absolute configurations were also determined by single-crystal X-ray analysis.

Synthesis,Crystal Structure and Fluorescence of a Bicyclic Product Containing Chromene and Propargylamine Skeleton

The bicyclic product containing a chromene skeleton and a propargylamine skeleton（C（22）H（22）N2O2） was synthesized from the double sites of terminal alkyne, piperazine derivative and formaldehyde via one-pot procedure. Its structure was characterized by ^1H NMR, ^13C NMR, IR and H RMS, and further confirmed by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P21/n with a = 12.6571（14）, b = 11.3249（12）, c = 12.6571（14） A, β = 105.22°,V = 1750.6（3） A^3, Z = 4, R = 0.0568 and w R = 0.1444. The fluorescence of the product was discussed.

The water-soluble bicyclic 2-pyridone-based fluorescent probe for fast and selective detection of hypochlorite

As a strong oxidizer,hypochlorite(Cl O^(-))are widely employed as bleaching agents and disinfectants.Determination of ClO^(-)is required to ensure bactericidal effects and avoid hazards caused by excessive residual chlorine.Herein,the derivative bicyclic 2-pyridone,namely DHIP-Py,was prepared successfully to establish a new ClO^(-)-quantitative method.The probe exhibits excellent Cl O^(-)selectivity over other ROS and anions/cations,high sensitivity(LOD=1.32μmol/L),fast response(<5 s),and wide-p H tolerance(pH4~10).Benefit from its good water solubility,DHIP-Py is well suited for water sample analysis and has been successfully applied to detect Cl O^(-)in real-world food and environmental samples,including tap water,bottled water and river water.The detection results were essentially identical to that of obtained from traditional DPD method.Moreover,visual detection of Cl O^(-)via filter paper-based solid sensor and imaging of ClO^(-)in Escherichia coli were also achieved by DHIP-Py.These satisfactory results demonstrate that this bicyclic 2-pyridone-based hypochlorite probe is a promising free chlorine chemosensor with great potential for analytical applications.

Rhodium-catalyzed enantio-and diastereoselective carboamidation of bicyclic olefins toward construction of remote chiral centers and axis

The precise control of multiple chiral elements through a single step catalytic process remains a significant challenge in asymmetric catalysis.Reported herein is rhodium-catalyzed three-component asymmetric carboamidation between aryl boronic acid,achiral strain-activated symmetric bicyclic olefins bearing a prochiral C-N or N-N axis,and dioxazolones.The reaction proceeded effectively in excellent enantio-and diastereoselectivity under mild conditions to produce the bicyclic framework with six contiguous chiral centers as well as a N-N or C-N chiral axis.The reaction featured excellent functional group tolerance,chemoselectivity,and stereoselectivity.Mechanistic studies indicated that the coupling system proceeded via initial transmetalation,followed by stereo-determining migratory insertion into the olefin and electrophilic amidation.

Organocatalytic enantioselective construction of bicyclic γ-butrolactones

An enantioselective organo-catalyzed reaction of furanones with α,β-unsaturated ketones has been established herein, which provides an efficient access to chiral bicyclic γ-butyrolactones in good yields, enantioselectivities and diastereoselectivities. Further transformations of product are demonstrated. A diamine mediated catalytic cycle is proposed.

Current development of bicyclic peptides

Bicyclic peptides,a class of polypeptides with two loops within their structure,have emerged as powerful tools in the development of new peptide drugs.They have the potential to bind to challenged drug targets,with antibody-like affinity and selectivity.Meanwhile,bicyclic peptides possess small molecule-like access to chemical synthesis,which is conducive to large-scale synthesis and screening.In the last five years,bicyclic peptide technology has been increasingly developed,and researchers have carried out a variety of studies to elucidate the potential functions of bicyclic peptides.With the continuous development of synthetic methods and the advances of new technology to build bicyclic peptide libraries,bicyclic peptides are now becoming widely used in the development of new drugs for various diseases.This perspective provides an overview of the structure types,synthesis and applications of bicyclic peptides in current drug development,and our own views on future challenges of bicyclic peptides.

Chiral Bicyclic Imidazole-Catalyzed Direct Enantioselective C-Acetylation of Indolones

By adjusting the bond angle and stereocontrol substituent of the chiral bicyclic imidazole catalysts,direct enantioselective C-acetylation of indolones and their sequencial pattern have been successfully developed.Indolones bearing a quaternary stereocenter were synthesized with satisfactory yields and excellent enantioselectivities(up to 97%ee).The reaction can be realized with 410 turnover numbers,and the products can be transformed into several functional compounds via simple derivations of the acetyl group.

The Laplacian spectral radii of unicyclic and bicyclic graphs with n vertices and k pendant vertices

In this paper,we determine graphs with the largest Laplacian spectral radius among the unicyclic and the bicyclic graphs on n vertices with k pendant vertices,respectively.

New Insights on the Mechanism of Thermal Cleavage of Unsaturated Bicyclic Diaziridines： A DFT Study

A DFT calculations are carried out at UB3LYP/6-311＋ ＋G （3df, 2p） levels of theory to study electrocyclic thermal cleavage of four （R） derivatives of unsaturated bicyclic diaziridines, Ix-R, to produce corresponding （Z） and （E） azomethine imides （2X-Z, 2X-E, 3X-Z and 3X-E）, where X=H, Me, t-Bu and Ph. Cleavage of 1X-R series to form the most stable 3X-Z product, （path 2） is found the favored procedure because of delocalized negative charge on five atoms and lower steric effect in related transition state. According to IRC calculations in paths 1 and 2, C6--N1 bond is cleaved before the rate determinating step （transition state）. The stability of unsaturated bicyclic diaziridines and their corresponding （Z） and （E） azomethine imides is in the following order in gas phase and chloroform, tetrahydrofuran, and acetone solvents： 3X-Z〈3X-F〈2X-Z 〈2X-E 〈 1X-R 〈 1X-S.

The Laplacian Spread of Bicyclic Graphs

The Laplacian spread of a graph is defined to be the difference between the largest eigenvalue and the second smallest eigenvalue of the Laplacian matrix of the graph. In our recent work, we have determined the graphs with maximal Laplacian spreads among all trees of fixed order and among all unicyclic graphs of fixed order, respectively. In this paper, we continue the work on Laplacian spread of graphs, and prove that there exist exactly two bicyclic graphs with maximal Laplacian spread among all bicyclic graphs of fixed order, which are obtained from a star by adding two incident edges and by adding two nonincident edges between the pendant vertices of the star, respectively.