Facile Addition of Dichloroketene to Acetylenes Mediated by Zinc and Ultrasound

The addition of dichloroketene, generated from trichloroacetyl chloride, zinc dust and ultrasound, to terminal and internal acetylenes is reported. This procedure is a more convenient alternative to Zn-Cu couple.     

Reaction pathways of the Simmons-Smith reaction

The cyclopropanation reaction of an alkene with a metal carbenoid has been studied by means of the B3LYP hybrid density functional method. The cyclopropanation of ethylene with a lithium carbenoid or a zinc carbenoid [Simmons-Smith (SS) reagent] goes through two competing pathways, methylene transfer and carbometalation. Both processes are fast for the lithium carbenoid, while, for the zinc carbenoid, only the former is fast enough to be experimentally feasible. The reaction of an SS reagent (ClZnCH(2)Cl) with ethylene and an allyl alcohol in the presence of ZnCl(2) was also studied. The allyl alcohol reaction was modeled with an SS reagent/alkoxide complex (ClCH(2)ZnOCH(2)CH=CH(2)) formed from the SS reagent and allyl alcohol. Two modes of acceleration were found. The first involves the well-accepted mechanism of 1,2-chlorine migration, and the second involves a five-centered bond alternation. The latter was found to be more facile than the former and to operate equally well both with ethylene and with aggregates of SS reagent/alkoxide complexes. Calculations on the SS reaction with 2-cyclohexen-1-ol offer a reasonable model for the hydroxy-directed diastereoselective SS reaction, which has been used for a long time in organic synthesis.     

Facile Preparation of Homoallyl Amines via Reaction of N-Aminoalkylbenzotriazoles with Allylsamarium Bromide

Homoallyl amines can be readily prepared in good to excellent yields via reaction of N-aminoalkylbenzotriazoles with allylsamarium bromide in THF at room temperature.     

Facile and Convenient One-pot Synthesis of 1,1-Disubstituted Cyclopropanes in Water

A facile and convenient one-pot synthesis method of substituted cyclopropanes in water has been developed.A series of 1,1-disubstituted cyclopropanes 3 were synthesized from the reaction of β-dicarbonyl compounds 1 with 1,2-dibromoethane 2,in very high yields catalyzed by tetrabutylammonium bromide(TBAB) at 50 oC in the presence of K2CO3 in water.The catalyst TBAB in the aqueous phase can be reused after the separation of organic products.     

系列纳米结构锰氧化物的水热合成

以KMnO₄为锰源、抗坏血酸(AA)为还原剂,采用水热法制备系列纳米结构锰氧化物。通过调节反应物的物质的量的比、水溶液的pH值、反应温度和反应时间,制备出了不同纳米结构的锰氧化物,包括Mn₃O₄纳米粒子、MnOOH、α-MnO₂和β-MnO₂纳米棒。采用XRD和TEM测试技术对合成产物进行了表征,同时对其反应机理进行了探讨。     

Preparation of Water-Soluble Polymers via the Mannich Reaction

The Mannich reaction, defined as the condensation of ammonia or a primary or secondary amine with formaldehyde and a compound containing at least one hydrogen atom of pronounced activity, was first shown to yield polymers from suitably selected reactants as early as 1946 [l]. Surprisingly, very few further attempts to utilize this interesting reaction in polymer formation have been reported in the literature.     

A Facile Synthesis of Aryl Ethers of Ethynyl-Carbinols Using the Mitsunobu Reaction

The facile synthesis of a few aryl ethers of ethynyl carbinols using the Mitsunobu reaction is reported.     

Facile Mechanochemical Preparation of Polyamide-derivatives via Solid-state Benzoxazine-isocyanide Chemistry

With the exploration of novel sustainable protocol for functional polyamides'(PAs) construction as the starting point, herein, the small molecular model compound(M1-ssBIC) was prepared firstly by manual grinding of monofunctional benzoxazine(1 a) and isocyanide(1 b) via solid-state benzoxazine-isocyanide chemistry(ssBIC) to evaluate the feasibility of ssBIC. Linear PAs(P1-series polymers) were subsequently synthesized from biunctional benzoxazine(2 a) and isocyanide(2 b), and the influence of the loading of catalyst(octylphosphonic acid)(OPA) on the polymerization was investigated. Afterwards, two kinds of cross-linked PAs were successfully constructed via ssBIC by using trifunctional benzoxazine(3 a) and cross-linked polybenzoxazine(4 a) as reaction substrates, respectively, thus verifying the adaptability of ssBIC. Structural characterization indicates that amide, phenolic hydroxyl and tertiary amine substructures, with metal-complexing capability, have been successfully integrated into the obtained PAs. A type of representative PA/silver composite(P3-AgNPs) was prepared subsequently via in situ reduction treatment, and its application as recyclable reduction catalyst for organic pollutant p-nitrophenol(4-NP) was preliminarily investigated here to provide the example for possible downstream application of ssBIC. We think that this current work could provide a new pathway for the construction of functional PAs through facile and sustainable ssBIC protocol.     

钴原子催化活化乙烷的反应机理

采用密度泛函理论B3LYP方法分别在两种不同基组水平上, 研究了Co原子催化乙烷反应的反应机理, 优化了反应过程中各反应物、中间体、过渡态和产物的构型, 并在同一水平上计算了反应中各驻点的振动频率, 运用自然键轨道理论(NBO)方法分析了各物质的成键情况和轨道间相互作用. 在两种不同基组水平上研究所得的反应历程及相应的能量变化趋势是一致的, 其活化过程可分为C—C键活化及C—H键活化, 分别释放出CH4和H2, 反应速控步骤的活化能后者较前者低, 因此, C—H键的活化较C—C 键活化容易进行.     

A Facile Synthesis of Aldehyde and Ketone via Senochemical Barbier Reaction and Oxidation

Methyl ketone is prepared by a sonochemical Barbier reaction of methyl iodide, magnesium powder and aldehyde in Benzene/THF (9/1) solvent in a commercial ultrasonic cleaning bath (39 kHz), followed by the addition of N-chlorosuccinimide (NCS) as an oxidizing agent.     

Facile Preparation of Substituted Allenic Esters via the Ortho Ester Claisen Rearrangement

Five substituted allenic esters were prepared in good yields through the ortho ester Claisen rearrangement of primary and secondary propargyl alcohols.     

A Convenient Procedure for the Preparation of Reactive Zinc for the Reformatsky Reaction

A reactive zinc powder is obtained by addition of ZnCl₂ to a lithium dispersion suspended in ether. Reformatsky Reactions with the zinc powder are described.     

A Facile and Clean Synthesis of Pyrimidine Derivatives via Three-component Reaction in Aqueous Media

A series of 5‐benzylidenepyrimidine‐2,4,6(1H,3H,5H)‐trione and 5,5′‐(arylmethylene) bis[6‐aminopyrimidine‐ 2,4(1H,3H)‐dione] derivatives were synthesized via the three‐component reactions of aromatic aldehyde, 6‐aminopyrimidine‐2,4‐dione and Medrum's acid in aqueous media in the presence of triethylbenzylammonium chloride. The structures of the products were affected by substituents of aromatic aldehydes.     

Facile Conversion of Tetrahydropyranyl and Silyl Ethers into Esters Using Acid Chlorides and Zinc Chloride

Tetrahydropyranyl and silyl ethers were cleanly converted into the corresponding esters using acid chlorides and a catalytic amount of zinc chloride in acetonitrile.     

后重氮偶合法制备咔唑类光折变聚合物

生色团;后重氮偶合法制备咔唑类光折变聚合物     

Convenient Preparation of Trans-1,3-Dioxadecalin via the Prins Reaction

The acid catalyzed condensation of cyclohexene with aqueous formaldehyde can be controlled on a preparatively useful scale to give a 60–80% yield of trans-1,3-dioxadecalin.     

Preparation of Allylstannanes and Distannanes Using Zinc in Liquid Ammonia

Abstract

Barbier-type reductive coupling of allylic bromides and organotin compounds can be carried out in liquid ammonia (?33°C) using commercial zinc powder. This procedure provide a new simple and environment-friendly method for the synthesis of allylstannanes and distannanes.     

Facile Synthesis of Polyhydroxylated Polybutadiene Derived from Hydroxyl-Terminated Polybutadiene via Thiol-Ene Click Reaction

Polyhydroxylated polybutadiene (PHPB) was synthesized via a thiol-ene click reaction between hydroxyl-terminated polybutadiene (HTPB) and 2-mercaptoethanol (ME) with 2,2’-azoisobutyronitrile (AIBN) as initiator. Effects of AIBN content, reaction time and temperature on the click reaction were investigated by determining hydroxyl value of the PHPB. The PHPB was characterized by FT-IR, ¹H-NMR, ¹³C-NMR and GPC. Relative reactivity of three types of C?C double bonds (1,2-vinyl, 1,4-cis and 1,4-trans units) in the HTPB reacting with the ME was discussed. The results showed that the optimal reaction conditions were that the AIBN content, reaction time and temperature were 2.0 wt%, 180 min and 70°C, respectively. Under these conditions, the hydroxyl value of the PHPB was 3.12 mmol·g^?1 when the HTPB/ME mass ratio was 10:2. All three types of C?C double bonds in the HTPB could react with the ME and the reactivity order was: 1,2-vinyl unit > 1,4-cis unit > 1,4-trans unit.