Substituent Effects on 13C NMR and 1H NMR Chemical Shifts of CH=N in Multi-substituted Benzylideneanilines

Fifty-three samples of multi-substituted benzylideneanilines XArCH=NArYs （abbreviated XBAYs） were synthesized and their NMR spectra were determined. An extensional study of substituent effects on the 1H NMR chemical shifts （δH（CH=N）） and 13C NMR chemical shifts （δc（CH=N）） of the CH=N bridging group from di-substituted to multi-substituted XBAYs was made based on a total of 182 samples of XBAYs, together with the NMR data of other 129 samples of di-substituted XBAYs quoted from literatures. The results show thatthe substituent specific cross-interaction effect parameter （△（∑σ）2） plays an important role in quantifying the δc（CH=N） values of XBAYs, but it is negligible for quantifying the δH （CH=N） values; the other substituent parameters also present different influences on the δc （CH=N） and （δH （CH=N）. On the whole, the contributions of X and Y to the δc （CH=N） of XBAYs are balanced, but the δH（CH=N） values of XBAYs mainly rely on the contributions of X.

Biomimetic Epxidation of Alkenes by Phenyliodonium Diacetate [PhI(OAc)_2] in the Presence of Mn(Ⅲ) Complex of meso-Tetrakis(4-methoxyphenylporphyrin) Acetate Mn[(T4-OCH_3P)P]OAc

We have reported that phenyliodonium diacetate[PhI（OAc）2] can serve as an eco-friendly mild oxidant for the epoxidation of alkenes in the presence of Mn（III） complex of meso-tetrakis（4-methoxyphenylporphyrin） acetate Mn[（T4-OCH3P）P]OAc and imidazole in CH2Cl2.The amounts of the products（%） and selectivities are very dependent upon the electronic and steric properties of the starting alkenes.To evaluate the validity of this catalytic system for C ＂H activation,cyclohexane and ethylbenzene were oxidized under the epoxidation conditions.

Hydrogenation of Alkenes with NaBH4, CH3CO2H, Pd/C in the Presence of O- and N-Benzyl Functions

NaBH4, CH3CO2H, Pd/C has been described as an effective reagent system to hydrogenate alkenes. Here, we show that the hydrogenation occurs chemoselectively, making it possible to hydrogenate alkenes under Pd/C catalysis with hydrogen created in situ without O- or N-debenzylation.

Tandem Lewis acid catalysis for the conversion of alkenes to 1,2‐diols in the confined space of bifunctional TiSn‐Beta zeolite

The generation of multifunctional isolated active sites in zeolite supports is an attractive method for integrating multistep sequential reactions into a single‐pass tandem catalytic reaction.In this study,bifunctional TiSn‐Beta zeolite was prepared by a simple and scalable post‐synthesis approach,and it was utilized as an efficient heterogeneous catalyst for the tandem conversion of alkenes to 1,2‐diols.The isolated Ti and Sn Lewis acid sites within the TiSn‐Beta zeolite can efficiently integrate alkene epoxidation and epoxide hydration in tandem in a zeolite microreactor to achieve one‐step conversion of alkenes to 1,2‐diols with a high selectivity of>90%.Zeolite confinement effects result in high tandem rates of alkene epoxidation and epoxide hydration as well as high selectivity toward the desired product.Further,the novel method demonstrated herein can be employed to other tandem catalytic reactions for sustainable chemical production.

Functional Polyethylene Glycol with Carboxyl-supported Platinum as an Efficient Catalysis System for the Hydrosilylation of Alkenes

A series of carboxylated long chain polyethylene glycols(abbreviated as PEGCOOH) has been synthesized and used to support chloroplatinic acid.These supported catalysts were then tested for their efficiency in the hydrosilylation of alkenes.The factors affecting their catalytic properties,e.g.relative molecular mass of polyethylene glycol,reaction temperature,platinum content,and type of alkenes,have been studied.It was found that the activity of the platinum catalyst decreased with increasing length of the polyethylene glycol chain,and increased with reaction temperature.Moreover,these catalysts could be reused several times without a noticeable decrease in activity or selectivity.The reaction pathway leading to excellent selectivity for the β-adduct of hydrosilylation of alkenes with triethoxysilane catalyzed by this catalysis system was discussed.

Efficient visible light initiated hydrothiolations of alkenes/alkynes over Ir_(2)S_(3)/ZnIn2S4:Role of Ir_(2)S_(3)

The hydrothiolations of alkynes/alkenes with thiols is an atom-economic and thus attractive method for the constructions of C‒S bonds.Here Ir_(2)S_(3)/ZnIn_(2)S_(4)nanocomposites with varied Ir_(2)S_(3)loadings were obtained by one-pot solvothermal method from ZnCl_(2),InCl_(3)and thioacetamide with IrCl_(3).The loading of Ir_(2)S_(3)on the surface of ZnIn_(2)S_(4)promoted the hydrothiolations of alkenes and alkynes,with an optimum performance observed over 0.5 mol%Ir_(2)S_(3)/ZnIn_(2)S_(4)nanocomposite.Based on the studies on the performance of several other cocatalysts(MoS2,NiS and Pd)loaded ZnIn_(2)S_(4)and the EIS analyses,it was proposed that the superior performance over Ir_(2)S_(3)/ZnIn_(2)S_(4)nanocomposite can be ascribed to an improved efficiency on the photogeneration of the thiyl radicals by loading Ir_(2)S_(3)as well as its inactivity for photocatalytic hydrogen evolution,a side reaction in the light initiated hydrothiolation reaction over ZnIn_(2)S_(4).This study not only demonstrates an efficient and green strategy to synthesize thiolated products under visible light based on semiconductor photocatalysis,but also provides some guidances for the design and development of photocatalytic systems for light induced organic syntheses.

Michael Addition of Amines to Activated Alkenes Promoted by Zn/NH_4Cl System

A Zn/NH4Cl system was exploited at room temperature to promote the Michael addition reaction of various primary and secondary amines with α,β-unsaturated esters,nitriles,amides,and ketones to give the corresponding saturated amines under the mild condition in high yield.

Ultrasonic-enhanced Stereoselective Debromination of vic-Dibromides to Alkenes with Metallic Zinc Powder in Aqueous Media

Carbon-carbon double bond functional groups are often protected through a popular bromination/debromination method because of their reactivity. An ultrasonic-enhanced stereoselective debromination of vic-dibromides with metallic zinc powder in aqueous media has been developed, which generates E-alkenes with excellent yields. The reactivity of vic-dibromides decreases in the order of 1,2-dibromo-1,2-diphenylethane>1,2-dibromo-1-phenylethane>1,2-dibromo-1,2-dialkylethane.

A DFT Study of Alkenes and Alkynes Reacting with H-GaN (0001) Surface

The addition reactions of alkenes and alkynes to the H-terminated GaN （0001） surface with a Ga dangling-bond have been studied employing periodic density functional theory （PDFT） calculations. Detailed information on the reaction pathways of these alkenes and alkynes with H-GaN （0001） surface is provided, which indicates that the reactions contain two steps separated by the metastable intermediates： elementary addition reaction and H-abstraction process. From the energy curves, the reactions are clearly viable in the cases of ethene, styrene and phenylacetylene; while for ethyne, the H-abstraction barrier is higher than the desorption barrier of the intermediate, so the adsorbed C2H2 in intermediate is more likely to be desorbed back into the gas phase than to form a stable adsorbed species. Furthermore, it is obvious that for either alkenes or alkynes, the systems substituted by phenyl have more stable intermediates because π conjugation could improve their stabilities.

Chiral Salen Manganese Complex Immobilized on SBA-15:A New Heterogenized Enantioselective Catalyst forthe Epoxidation of Alkenes

Jacobsen's catalyst was immobilized onto SBA-15 by multi-step grafting, and this heterogenized catalyst exhibited comparable catalytic performance with the corresponding homogeneous counterpart for the epoxidation of alkenes, and the catalyst could be recycled effectively several times.

(Z)-a-Selanyl Alkenyl Grignard Reagents as Convenient Precursors for Stereoselective Synthesis of Trisubstituted Alkenes

Z)-a-Selanyl alkenyl Grignard reagents 2 were prepared conveniently by treatment of a-bromovinylselenides 1 with magnesium filings in THF. Intermediates 2 were reacted with alkyl iodides in the presence of CuI or Pd(PPh3)4 to afford (Z)-1,2-disubstituted vinylselenides 3, which were cross-coupled with Grignard reagents in the presence of (PPh3)2NiCl2 to give trisubstituted alkenes 4 stereoselectively in good yields.

Asymmetric Baylis-Hillman Reaction between Chiral Activated Alkenes and Aromatic Aldehydes in Me_(3)N/H_(2)O/Solvent Medium

Chiral activated alkene, L-menthyl acrylate and （＋）-N-α-phenylethyl acrylamide, induced asymmetric Baylis-HiUman reaction of aromatic aldehydes was realized at 25℃ for 7 days in Me3N/H2O/solvent homogeneous medium. The corresponding Baylis-Hillman adducts were obtained in good chemical yield with moderate to excellent diastereoselectivity （up to 99% de）.

A New Method for the Transformation of Alkenes intoα, β-Unsaturated Ketones via Cycloaddition with Dichloroketene

A new synthetic method is described here to obtain α, β-unsaturated ketones through alkenes through a sequence involving f (1) cycloaddition of alkenes with dichloroketene, (2) dechlorination of adducts, (3)acidpromoted ring-opening isomerization ofcyclobutanones in CF3 CO2H.

Zirconium-Mediated Synthesis of Multi-substituted Dibenzosilole and Benzonaphthosilole Derivatives

In this study, a new zirconium-mediated cycloaddition for preparing dibenzosilole derivatives was developed using siliconbridged diynes and electron-withdrawing alkynes as starting materials. The preparation of silicon-bridged diynes from 1-bromide-2-iodobenzene, terminal alkynes, and dimethyldichlorosilane was also studied. Unlike in the previous synthesis methods, much higher yields of electron-withdrawing group-substituted dibenzosilole derivatives were obtained. In addition, a new synthesis strategy for preparing benzonaphthosilole derivatives using internal alkynes, 1,4-dibromobenzene, and electron-withdrawing alkynes as starting materials is proposed. Compared with previous methods, alkyl, phenyl, and electron-withdrawing groups can be successfully introduced onto aromatic rings, and the positions of these substituents can be easily controlled. The cycloaddition reactions for dibenzosilole and benzonaphthosilole derivatives are highly efficient one-pot processes, and the raw materials are available and easily prepared. Using these new methods, a series of novel multisubstituted dibenzonsilole and benzonaphthosilole derivatives were obtained effectively.

'STEREOSELECTIVE SYNTHESIS OF TRISIJBSTITUTED ALKENES VIA,TITANOCENOCYCLES

By previously reported modified Masai-Rausch method of synthesizing titanocenocycles,followed by acid hydrolysis,trisubstituted al-kenes were synthesized,yields obtained are higher than that reported in literatures.Starting from unsymmetrical alkyne substrates,twelve different types of substituted alkenes were synthesized,among which only two were found single component,others were of mixed isomers.Beside conventional analytical methods,the NMR spectral analysis of titanocenoheterocycle intermediates and the products were used to identify the isomeric structures as well as their relative contents.

ORGANOPHOSPHINE INITIATED REACTION OF PERFLUOROALKYL IODIDES WITH ALKENES

perfluoroalkyl iodides reacted with alkenes in acetonitrile solu- tion containing catalytic amount of organophosphine under mild condition to give the corresponding adducts in moderate to good yields.Reaction was shown to involve a free radical mechanism.

STUDY ON Cp_2TiCl_2/Fe-INITIATED ADDITION OF 2-HALOTETRAFLUOROETHYL IODIDES TO ALKYNES AND ALKENES

Initiated by CP_2TiCl_2/Fe redox system,2-halotetrafluoroethyl iodides readily reacted with alkynes or alkenes to give 1:1 adducts in good to excellent yields.

INSERTION OF PTC-GENERATED DICHLOROCARBENE INTO C-B BO ND.A FACILE SYNTHESIS OF KETONES FROM ALKENES VIA ORGANOBORATES

The insertion of dichlorocarbene generated from chloroform by Phase Transfer Catalysis(PTC)into carbon-boron bond of dialkylborate anions 3,obtained by method A and B,resulted in the formation of the inter- mediates 5,which were oxidized with alkaline hydrogen peroxide to give the corresponding dialkylketones in 36-77.9% yields.

烯烃的可调控区域选择性7-endo或6-exo碘环化有机综合实验设计

该文将科研成果“烯烃的可调控区域选择性7-endo或6-exo碘环化反应”设计转化为有机综合教学实验。考察了溶剂、温度、碱以及气体氛围对反应选择性和实验结果的影响。这种对相同实验进行对比研究的有机合成方法学策略,不仅能够使学生实践科研有机合成实验的基本过程,调动学生的学习积极性,培养科研创新能力和综合实践能力,还很好地实现了教学实验与科研实验的结合。