Syntheses of 2- or 6-Substituted Chromones and Chromone Ring-opening Reaction in Polyphosphoric Acid

In an attempt to find new antitumor agents,a novel class of chromone compounds with a benzimidazole or a benzoxazole ring in positions 2 or 6 were synthesized via condensation in polyphosphoric acid(PPA) by using chromone acids as the starting materials. During the preparation process,it was found that PPA could cleave the chromone ring to produce a ring-opening compound(6). The molar ratio of the chromone compound(5) to the ring-opening compound(6) varied with the change of reaction temperature and time. Based on MTT protocol,the antitumor activity of each of the compounds obtained was evaluated against three human cancer cell lines: KB(oral epidermal),A2780(ovary) and Bel7402(liver). The IC_ 50 varied from 54.7 μmol/L to more than 180 μmol/L.

Carbene-Catalyzed Asymmetric Ring-Opening Reaction of Biaryl Lactams to Access Axially Chiral Biaryls

Axially chiral biaryls represent the most important class of atropisomers,and they widely exist in natural products and biologically active molecules.They also constitute a unique scaffold for chiral ligands and catalysts in organic synthesis.The development of synthetic methods to obtain such chiral compounds has received widespread attention,among which catalytically atroposelective ring-opening of configurationally labile compounds represents one of the most attractive strategies.Various substrates with strained cyclic structures,such as the renowned Bringmann's lactones,can undergo asymmetric transformation into stable atropisomers.Known advancement primarily relies on metal catalyst combined with well-designed chiral ligands,the approaches utilizing organocatalysis as a critical resolution strategy are notably scarce.In this study,we disclosed a N-heterocyclic carbene(NHC)-catalyzed asymmetric ring-opening reaction of biaryl lactams via direct atroposelective nucleophilic activation.The optimized bulky carbene catalyst ensures that the reaction can proceed under mild conditions,affording the desired product with good to excellent yields and atroposelectivity.

Study on Unexpected Cycloaddition Reactions of Imines with THF

An unexpected tricyclic compound 2,3,3a,4,5,9b-hexahydrophenylfuro[3.2-c] quinoline 4 and its aromatized product 6 were obtained when the cycloaddtion of imine 1 and substituted norbornene 2 was carried out in THF with a catalytic amount of boron trifluoride. The structures of the products were determined by spectral data and the mechanism of reaction was substantiated by the imitation reaction.

Preparation of nucleoside-pyridine hybrids and pyridine attached acylureas from an unexpected uracil ring-opening and pyridine ring-forming sequence

Novel pyrimidine nucleoside-3,5-dicyanopyridine hybrids （4） or pyridine attached acylureas （5） were selectively and efficiently prepared from the reaction of 2′-deoxyuddin-5-yl-methylene malononitrile （1）, malononitrile （2） and thiophenol （3） or from an unexpected uracil ring-opening and pyddine ring-forming sequence via the reaction of 1 and 3. It is the first time such a sequence has ever been reported.

TARTARIC ACID TEMPLATED SYNTHESIS OF MESOPOROUS Ti-INCORPORATED SILICA AND ITS CATALYTIC ACTIVITY FOR THE RING-OPENING POLYMERIZATION OF ε-CAPROLACTONE

Ti-incorporated mesoporous silica materials with pore diameters of 3-4 nm have been prepared via the co-hydrolysis and co-condensation reactions, that is the sol-gel reactions, of titanium (IV) tetrabutoxide and tetraethylorthosilicate in the presence of tartaric acid as template, followed by extraction with ethanol to remove the templatemolecules. The materials were characterized in detail by Fourier transform infrared spectroscopy, nitrogen adsorption-desorption test, powder X-ray diffraction, transmission electron microscopy and X-ray energy dispersive spectroscopy. Theresults indicate that the Ti-containing silica materials have large specific surface areas (ca. 1200 m^2 g^(-1)) and pore volumes(ca. 0.900 cm^3 g^(-1)). The mesoporosity arises from disordered interconnecting channels or pores. The Ti-incorporated silicasexhibit catalytic activity for the ring-opening polymerization of ε-caprolactone, otherwise, the pure mesoporous silicamaterial shows no catalytic activity under the identical conditions.

用LF-NMR研究三苯基铋对BAMO-THF/TDI黏结剂体系的固化反应

制备了4个BAMO-THF/TDI黏结剂体系（样品A、B、C、D）,固化催化剂三苯基铋（TPB）的质量分数分别为0.25%、0.50%、1.00%、2.00%。用低场核磁共振（LF-NMR）技术,通过在线监测样品A、B、C、D中聚合物链上氢质子的横向弛豫时间T2,研究了每个样品50、60、70、80℃时的固化反应动力学。结果表明,T2与体系固化反应程度有相关性,可在线监测样品固化反应的全过程。样品的固化反应可分为3个阶段,第1阶段为二级动力学反应,第2、3阶段均为一级动力学反应,TPB含量一定、50-80℃时,反应速率常数k与固化温度有明显的正相关性,其中第3阶段k对固化温度的变化更敏感。TPB质量分数在0.25%-2.00%、固化温度为50-80℃时,固化反应机理一致,没有改变交联网络,但TPB质量分数不小于1.00%或固化温度为80℃时样品中极易出现气泡。

Pd(I)-catalyzed ring-opening arylation of cyclopropyl-α-aminoamides:Access toα-ketoamide peptidomimetics

We report the unprecedent Pd(I)catalyzed ring-opening arylation of cyclopropyl-α-aminoamides.This protocol allows facile access to biologically important α-ketoamide-containing oligopeptides and even more challenging peptide-natural product conjugates.Site selectivity was achieved by introduction of special unnatural amino acids,which also meets the requisite of bioorthogonal chemistry.Mechanism investigations reveals a distinct domino radical ring-opening process through Pd(I)catalysis.

Epoxidation of Styrene-Isoprene-Styrene Block Copolymer and Research on Its Reaction Mechanism

Styrene-isoprene-styrene（SIS） block copolymer was modified into epoxidized styrene-isoprene-styrene（ESIS） block copolymer with performic acid generated in situ from hydrogen peroxide and formic acid.The structure and property of ESIS were characterized by Fourier transform infrared（FT-IR） spectroscopy,gel permeation chromatography（GPC）,thermogravimetric/differential thermogravimetric（TG/DTG）,melt flow rate（MFR） and dynamic mechanical analysis（DMA）,and the reaction mechanism in the process of epoxidation was analyzed.The results showed that C=C double bonds of 1,4-structure were more active than that of 3,4-structure in polyisoprene chains.With epoxidation reaction proceeding,the whole tendency of molecular weight increased and molecular weight distribution widened,and MFR firstly increased and latterly decreased.The heat resistance of ESIS was superior to that of SIS.When SIS was changed into ESIS with 15.3% of mass fraction of epoxide groups,Tg of polyisoprene chains increased from-45.3 ℃ to 10.9 ℃.In the earlier period of epoxidation,some molecular chains ruptured and new substances with low molecular weight formed.However,in the latter period,crosslinking reaction between molecular chains which was initiated by epoxide groups or C=C double bonds occurred and crosslinked insoluble substances came into being.

PENTAFLUOROBENZENESULFONYL BROMIDE AND ITS REACTIONS

Pentafluorobenzenesulfonyl bromide was synthesized by the reaction of pentafluorophenylmagnesium chloride with sulphur dioxide followed by bromine oxidation. The sulfonyl bromide reacted with polyfluorophenoxide to form polyfluorophenyl pentafluorobenzenesulfonates. Photolysis of pentafluorobenzenesulfonyl bromide gave bis(pentafluorobenzene)sulfone and decafluorodiphenyl.

LOW-VALENT TITANIUM INDUCED REDUCTIVE REACTION OF THIOCYANATES AND ISOCYANATE

Low-valent titanium reagent prepared from titanium tetrachloride and zinc was empolyed to induce the coupling reaction of thiocyanates with tetrahydrofuran yield alkyl 4-hydroxy butyl sulfide and isocyanate yield substituted urea.

THE INTRAMOLECULAR COUPLING REACTION OF 2-NITROETHYL-1, 3-DICARBONYL COMPOUND INDUCED BY LOW-VALENT TITANIUM

Low-valent titanium reagent prepared in situ from TiCl_4 and Zn was employed to induce the intramolecular coupling of nitro group with carbonyl group to give substituted hydroxyl pyrrolines, pyrroles and lactam in good yields.

LOW-VALENT TITANIUM INDUCED REDUCTIVE CROSS-COUPLING REACTION OF ACYL CHLORIDES WITH DIARYL KETONES

Treatment of acyl chlorides and diaryl ketones with an activated Ti(o)reagent,prepared by reduction of TiCl_4 with Zn powder,effects an intermolecular reductive cross-coupling reaction leading to ketones.

Polymerization of Dicyclopentadiene by Reaction Injection Molding

Dicyclopentadiene was polymerized by reaction injection molding (RIM) using a catalyst system based on molybdenum (V) chloride and anhydrous aluminum chloride and triethylaluminum. The effect of the reaction temperature on the polymer network and the type of the polymerization were discussed.

A Novel Example of Hetero Diels-Alder Reaction

2, 3, 3a, 4, 5, 9b-hexahydro-8-(N-methylsulfamylmethyl)-4-phenylfuro[3, 2-c]quinoline was obtained when the alkylation of compound 1 was carried out with THF as solvent. The structure of the product was determined and the mechanism of the reaction was studied and proved by the imitation reaction.

Facile access to β-hydroxyl ketones via a cobalt-catalyzed ring-opening/hydroxylation cascade of cyclopropanols

A cobalt-catalyzed ring-opening/hydroxylation cascade of highly strained cyclopropanols has been developed for the first time. The reaction was conducted under open-air atmosphere to afford a broad series of structurally diverse β-hydroxy ketones in moderate to good yields with high regioselectivity.The protocol features mild reaction conditions, simple operation, high-functional-group tolerance, facile scalability, and heterocycle compatibility.

Uniform Metal Sulfide@N-doped Carbon Nanospheres for Sodium Storage: Universal Synthesis Strategy and Superior Performance

Nitrogen-doped carbon-coated transition-metal sulfides(TMS@NCs)have been considered as efficient anodes for sodium-ion batteries.However,the uncontrollable morphology and weak core-shell binding forces significantly limit the sodium storage performance and life.Herein,based on the reversible ring-opening reaction of the epoxy group of the tertiary amino group-rich epoxide cationic polyacrylamide(ECP)at the beginning of hydrothermal process(acidic environment)and the irreversible ring-opening(cross-linking reactions)at the late hydrothermal period(alkaline environment),47 nm-sized ZnS@NCs were prepared via a one-pot hydrothermal process.During this process,the covalent bonds formed between the ZnS core and elastic carbon shell significantly improved the mechanical and chemical stabilities of ZnS@NC.Benefiting from the nanosize,fast ion/electron transfer,and high stability,ZnS@NC exhibited a high reversible capacity of 421.9 mAh g^(−1) at a current density of 0.1 A g^(−1) after 1000 cycles and a superior rate capability of 273.8 mAh g^(−1) at a current density of 5 A g^(−1).Moreover,via this universal synthesis strategy,a series of TMS@NCs,such as MoS_(2)@NC,NiS@NC,and CuS@NC were developed with excellent capacity and cyclability.

Tracking the Process of Domino Ring-Opening and Coupling of Fused Imidazole and Direct Observation of Peroxide Intermediates

Comprehensive Summary,A domino ring-opening and coupling of imidazolyl annulated heterocycles 1(1a:4-methyl-1-(1-methyl-1H-benzo[d]imidazol-2-yl)-4H-benzo[d]imidazo[1,5-a]imidazole,1b:1-(1,5-dimethyl-1H-benzo[d]imidazol-2-yl)-4,7-dimethyl-4H-benzo[d]imidazo[1,5-a]imidazole)with dioxygen was developed at solvothermal condition,leading to conjugated 1,2-diamidoalkenes derivatives 2((E)-ArCONHArC=CArNHCOAr(Ar:1-methyl-1H-benzo[d]imidazolyl(2a),1,5-dimethyl-1H-benzo[d]imidazolyl(2b)))as single crystals directly.The reaction process was tracked by electrospray ionization mass spectrometry(ESI-HRMS)and a series of reaction intermediates are detected.^(18)O_(2) labeling experiment verified the source of oxygen in 2.Combining evidence from control experiments,nuclear magnetic resonance(NMR)tracking,and crystallography,a seven-step reaction pathway involving oxygen addition,ring opening,Friedel-Crafts alkylation,oxidation,and dehydration was proposed and further supported by DFT calculation.

Platinum-Catalyzed Asymmetric Ring-opening Reaction of Oxabenzonorbornadiene with Terminal Alkynes

A novel platinum-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadiene with terminal alkynes is described.The reaction affords optically active cis-2-alkynyl-1,2-dihydronaphthalen-1-ols in moderate yields with good enantioselectivity in the presence of catalytic amounts of Pt(COD)Cl_(2)/(S)-BINAP and an excess of zinc powder.The products were obtained exclusively with the relative cis-configuration of the ring substituents and the prevalent(1R,2S)-configuration of the stereocenters,as determined by single crystal X-ray diffraction analysis.

A semiclassical molecular dynamics of the photochromic ring-opening reaction of spiropyran

The photochromic ring-opening reaction of spiropyran（SP） has been investigated by a realistic semiclassical dynamics simulation,accompanied by SA3-CASSCF（12 10）/MS-CASPT2 potential energy curves（PECs） of S0–S2.The main simulation results show the dominate pathway corresponds to the ringopening process of trans-SP to form the most stable merocyanine（MC） product.These findings provide more important complementarity for interpreting experimental observations.

Functionalized Polyphosphoester via Living Ring-opening Polymerization and Photochemical Thiol-ene Click Reaction

Poly(ethylene phosphonate)was synthesized via the living ring-opening polymerization of cyclic phos-phonate monomer catalyzed by organocatalyst.The pendant vinyl ftmctionalities were employed to perform the pho-tochemical click reactions wi&tMols.We demonstrated that both small thiol molecules and macromolecular thiols could be efficiently coupled into the PPE side chains,enabling the rapid and efficient functionalization of polyphos-phoesters(PPE).