Synthesis and properties of novel ditopic polypyridine ligands bridged by one and two acetylenic bonds

Ethynyl substituted bipyridine chelates react with bromo or triflate functionalized bipyridine or terpyridine subunits, in the presence of catalytic amounts of Pd^o(PPh₃)₄ to yield, the new homo- and heteroditopic ethynyl bridge ligands 2a, 4a, 7a and 8. Self coupling of the ethynyl substituted bipyridine species in the presence of CuCl/TMEDA/O₂, yield the symmetric diethynyl bridge ligands 2b, 4b and 7b.     

A Short and Convenient Synthesis of 5-Alkyl Substituted 8-Hydroxyquinolines

5-Chloro-8-methoxyquinoline undergoes rapid and reversible lithium-halogen exchange reaction with alkyllithiums to yield 5-alkyl substituted derivatives indirectly, whereas the reaction with phenyllithium is slower and 5-alkyl substituted compounds are formed by the direct addition of alkyl halides.     

Formation of Substituted Oxa‐ and Azarhodacyclobutanes

The preparation of substituted oxa‐ and azarhodacyclobutanes is reported. After exchange of ethylene with a variety of unsymmetrically and symmetrically substituted alkenes, the corresponding rhodium–olefin complexes were oxidized with H₂O₂ and PhINTs (Ts=p‐toluenesulfonyl) to yield the substituted oxa‐ and azarhodacyclobutanes, respectively. Oxarhodacyclobutanes could be prepared with excellent selectivity for incorporation of the oxygen atom on the more substituted carbon atom of the alkene. At the same time, azarhodacyclobutanes showed good‐to‐excellent selectivity for heteroatom incorporation on the less substituted carbon. Furthermore, it was shown that steric modifications of the ancillary ligand have a significant influence on the selectivity of Rh–olefin complex formation as well as formation of the substituted azametallacycles.     

Convenient One‐Pot Protocol for an Exclusive Synthesis of 4‐Cyano/ethoxycarbonyl‐2,2‐dimethyl‐2H‐chromene and/or 3‐Cyano/ethoxycarbonyl‐2‐isopropyl‐benzo[b]furan from a Single Oxo‐ylide

[{2‐(Fluoroaryloxy)‐2‐methyl‐propanoyl}‐(cyano/ethoxycarbonyl) methylene]triphenylphosphoranes underwent microwave‐assisted tandem intramolecular Wittig and Claisen rearrangement and internal cyclization reactions to afford fluoro‐substituted 2,2‐dimethyl‐2H‐chromenes and/or 2‐isopropyl‐benzo[b]furans in good yield. Upon controlled microwave irradiation in the presence of Nafion H catalyst in xylene, the oxo‐ylides selectively formed 4‐cyano/ethoxycarbonyl‐2,2‐dimethyl‐2H‐chromenes. Microwave irradiation of the same oxo‐ylide in the presence of K₂CO₃ as catalyst or in a polar solvent–like sulfolane resulted in the exclusive formation of the corresponding fluoro‐substituted 3‐cyano/ethoxycarbonyl‐2‐isopropyl‐benzo[b]furans.     

A novel one-pot synthesis of substituted 4-t-butyldimethylsilyloxy-thiazoles

The reaction of 2-halo-acylimidazolides or halides with primary thioamides in base give 2-halo-N-acylthioamides, which cyclize to the substituted 4-thiazolones and are trapped as the novel 4-t-butyldimethylsilyloxythiazoles in fair to good yield. The 2-aryl-4-t-butyldimethylsilyloxythiazoles undergo a [4+2] cycloaddition reaction with dimethoxyacetylene dicarboxylate [DMAD] to give substituted 2-pyridones in fair yield.     

5-Substituted-3-(substituted)phenyl-1,3,4-oxadiazolin-2(3H)-ones. Synthesis and reactions with nucleophilic reagents

A new synthesis of 4,4-dialkyl-2-(substituted)phenylsemicarbazides has been developed. The procedure begins with a 5-substituted-3-(substituted)phenyl-1,3,4-oxadiazolin-2(3H)-one, 3 , which is treated with dialkylamine to give a 1-acyl-4,4-dialkyl-2-(substituted)phenylsemicarbazide, 7 . Subsequent base-catalyzed hydrolysis of 7 gives 4,4-dialkyl-2-(substituted)phenylsemicarbazides, 14 , in high yield. With a variety of nucleophilic reagents, the compounds 3 also undergo ring opening.     

Diastereoselective one-pot synthesis of 7- and 8-substituted 5-phenylmorphans

Novel 7- and 8-alkyl and aryl substituted 5-phenylmorphans were synthesized from substituted allyl halides and N-benzyl-4-aryl-1,2,3,6-tetrahydropyridine by a highly efficient and diastereoselective reaction series, "one-pot" alkylation and ene-imine cyclization followed by sodium borohydride reduction. Mild cyclization conditions gave the desired substituted 5-phenylmorphans in good yield as a single diastereomer.     

Cu(II)-catalyzed one-pot synthesis of fully substituted dihydrothiophenes and thiophenes from thioamides and enynones

A facile and direct synthetic method was developed for the construction of fully substituted dihydrothiophenes, which via a copper-catalyzed Michael addition/intramolecular cyclization/protonation cascade reaction of readily available thioamides with enynones under air atmosphere. This approach provides 2,3-dihydrothiophenes with up to 92% yield in a one-pot process. In addition, several fully substituted thiophenes could also be synthesized by changing the substituents of thioamides.     

Direct synthesis of chiral aziridines from N-tert-butyl-sulfinylketimines

The direct preparation of a range of variously substituted chiral tert-butylsulfinylketimines was achieved in good yield (41-90%), with relatively rapid reaction times (4-15 hours); their synthetic application was examined through the reaction with the ylides derived from trimethylsulfonium iodide and S-allyl tetrahydrothiophenium bromide, affording convenient access to a diverse range of highly substituted chiral aziridines in up to 78% yield and > 90% d.e.     

Scope and limitations of a novel synthesis of 3-arylazonicotinates

The reaction of 3-oxo-3-phenyl-2-phenylhydrazonal with functionally substituted and heteroaromatic substituted acetonitrile to yield arylazonicotinic acid derivatives and 5-arylsubstituted pyridines was established. In some cases the produced nicotinates could not be isolated as they underwent thermally induced 6π-electrocyclization yielding polynuclear pyridine derivatives.     

Synthesis of new substituted cylopentenone derivatives via a one-pot three-component reaction between arylglyoxals,acetylacetone, and amines in aqueous media

An efficient one-pot method for the synthesis of new substituted cylopentenone derivatives is described via reaction of arylglyoxals and acetylacetone with aliphatic amines. This reaction was carried out in aqueous media in the absence of any catalyst or promoter to produce substituted cylopentenone in high yield.     

Studies on the Simultaneous Synthesis of Dimethyl Carbonate and Poly（ethylene terephthalate）： I. Catalytic Activity of Metal Acetate in Transesterification of Ethylene Carbonate with Dimethyl Terephthalate

Dimethyl carbonate (DMC) is a new building block of organic synthesis, as an environmentally benign compound and unique intermediate, it has been attracted much attention. Among the various methods for synthesizing DMC, transesterification of ethylene car…     

A new synthesis of gamma-lactams based on the reaction of vinyl sulfilimines with dichloroketene

The reactions of several aryl-, furanyl-, and vinyl substituted sulfilimines with dichloroketene proceeded at 25 degrees C to yield thioalkyl substituted gamma-lactams which, in turn, were converted to a variety of nitrogen-containing substrates. [reaction: see text]     

Δ<Superscript>2</Superscript>-isoxazolines from arylcyclopropanes: III. Phenylcyclopropanes substituted in three-membered ring in reaction with nitrosyl chloride activated with oxides of sulfur(IV,VI)

The reaction of phenylcyclopropanes substituted in the three-membered ring with nitrosyl chloride activated with sulfur(IV, VI) oxides provided in good yield substituted 5-phenylisoxazolines as a mixture of structural isomers.     

Palladium-catalysed coupling reaction of allenic alcohols with aryl- and alkenylboronic acids

The direct coupling of aryl- and alkenylboronic acids with allenic alcohols has been achieved using a palladium catalyst to yield various substituted dienes and trienes in high yields.     

高稳定性CaO-ZrO2固体碱催化剂的表征和催化性能

用共沉淀法经高温焙烧制备了CaO摩尔分数从10%至50%的CaO-ZrO₂系列催化剂, 将其应用于碳酸丙烯酯和甲醇酯交换合成碳酸二甲酯过程, 并通过XRD, FT-IR, BET, ICP, CO₂-TPD, XPS等表征手段研究了催化剂的物性及其催化性能随组成变化的的规律. 结果表明, 当CaO摩尔分数高于30%时, 表面出现游离的CaO, 虽然具有强碱性和高活性, 但是稳定性差; 而当CaO摩尔分数低于30%时, Ca^2＋进入ZrO₂晶格, CaO与ZrO₂形成连续固溶体, 并且随着CaO含量的增加, 晶格氧的电荷密度增加, 催化剂的碱性增强, 使得CaO-ZrO₂催化剂在碳酸丙烯酯和甲醇酯交换合成碳酸二甲酯过程中获得了高活性和高稳定性.     

Synthesis of new thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing epoxide pendant groups

A new class of thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing pendant epoxide groups were synthesized and characterized. These new epoxy polymers were prepared through the bromination of poly(2,6‐dimethyl‐1,4‐phenylene oxide) in halogenated aromatic hydrocarbons followed by a Wittig reaction to yield vinyl‐substituted polymer derivatives. The treatment of the vinyl‐substituted polymers with m‐chloroperbenzoic acid led to the formation of epoxidized poly(2,6‐dimethyl‐1,4‐phenylene oxide) with variable pendant ratios, and the structures and properties were studied with nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The ratios of pendant functional groups were tailored for the polymer properties, and the results showed that the glass‐transition temperatures increased as the benzylic protons were replaced by bromo‐, vinyl‐, or epoxide‐functional groups, whereas the thermal stability decreased in comparison with the original polymer. Within a molar fraction of 20–50%, the degree of functionalization had little effect on the glass‐transition temperature; however, it correlated inversely with the thermal stability of each functionalized polymer. The thermal curing behavior of the epoxide‐functionalized polymer was enhanced by the increment of the pendant functionality, which resulted in a significant increase in the glass‐transition temperature as well as the thermal stability after the curing reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5875–5886, 2006     

Enaminones as building blocks in organic synthesis: A novel route to polyfunctionally substituted benzonitriles,pyridines, eneylbenzotriazoles and diazepines

An efficient synthesis of enaminones 1a‐c is reported. Compounds 1a‐c reacted with diefhyl‐3‐amino‐2‐cyanopenten‐1,5‐dicarboxylate ( 3 ) to yield the benzonitriles 6 . On the other hand, the reaction of la‐c with 3‐amino‐2‐cyano‐2‐pentene dinitrile ( 7 ) afforded a mixture of benzonitriles 10 and pyridines 9 . The reaction of la‐c with 3‐aminocrotononitrile 11 has afforded the 4‐substituted‐3‐cyano‐2‐methylpyridines 15a‐c . The reaction of ethylene diamine with la‐c afforded 5‐substituted‐2,3‐dihydro‐lH‐[1,4]diazepines 18a‐c . On the other hand, la‐c reacted with o‐phenylenediamine to yield the 4‐(2‐aminopheynlamino)‐substituted enaminones 21 . Compounds 21 could be converted into the benzotriazolylenones 22 on treatment with sodium nitrite in acetic acid solution.     

Rhodium(I) catalyzed four-component reaction of Fischer alkenyl carbene complexes and 1,1-diphenylallene

Alkyl substituted chromium Fischer carbene complexes react with 1,1-diphenylallene in the presence of rhodium(I) catalysts (10 mol%) to yield highly substituted dienyl indenone derivatives. In this process a catalytic chromium(0)-rhodium(I) exchange occurs, four new C-C bonds are created, and four-components (two allenes, the carbene ligand and one CO ligand) are joined in a chemo- and regioselective manner.     

A new method for the preparation of 2-thio substituted furans by methylsulfanylation of gamma-dithiane carbonyl compounds

Several related methods for the preparation of differentially substituted 2-thiofurans are described. The general procedure involves the formation of a thionium ion from a gamma-dithianyl substituted carbonyl compound followed by cyclization of this reactive intermediate onto the tethered carbonyl group. Two methods for thionium ion generation were explored. One of these involved an acid-catalyzed reaction of beta-ketenedithioacetals, prepared from the condensation of 2,2-bis(methylsulfanyl)acetaldehyde with a variety of ketones. Cyclization followed by loss of methane thiol gave 2-thiofurans 17, 18 and 23, 24 in 70-90% yield. Attempts to prepare 5-heteroatom substituted 2-thiofurans from the corresponding beta-ketenedithioacetal amides or esters were unsuccessful, leading to 1,2-thio rearranged products. A more successful route involved the reaction of beta-acetoxy-gamma-thianyl carbonyl compounds with dimethyl(methylthio)sulfonium tetrafluoroborate (DMTSF). Treatment of the dithiane with this reagent resulted in the smooth generation of a thionium ion. Cyclization followed by loss of acetic acid afforded thiofurans 17, 18, 23, 47-49, 51, and 61-64 in 40-100% yield. The N-butenyl substituted thioamido furan furnished a rearranged hexahydropyrroloquinolin-2-one in high yield when heated at 110 degrees C.