Synthesis and Characterization of α,ω‐Heterofunctional Poly(ethylene oxide) Macromonomers

A novel α,ω‐heterofunctional poly(ethylene oxide) (PEO) macromonomer possessing methacryloyl and thienyl end groups was prepared by ring‐opening polymerization of ethylene oxide initiated by potassium thienylethoxide and termination of the living PEO ends with methacryloyl chloride. Incorporation of methacryloyl and thienyl groups was confirmed by free‐radical and oxidative polymerization processes, respectively, and by means of ¹H NMR analysis.

     

Synthesis of Phenanthrene Derivatives through the Reaction of an α,α‐Dicyanoolefin with α,β‐Unsaturated Carbonyl Compounds

Phenanthrene derivatives were prepared by reacting an α,α‐dicyanoolefin with different α,β‐unsaturated carbonyl compounds resulting from Wittig reaction of ninhydrin and phosphanylidene or condensation of barbituric acid and an aldehyde. The easy procedure, mild and metal‐catalyst free, reaction conditions, good yields, and no need for chromatographic purifications are important features of this protocol. The structures of the product of type 3 and 5 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Scheme 1).     

Comparison of Methionine α,γ‐Lyase and Homocysteine α,γ‐Lyase for Electrochemical Determination of Homocysteine

Recently, a novel enzymatic method was developed for determination of homocysteine. This method utilizes the electrochemical hydrogen sulfide sensor along with methionine α,γ‐lyase to accomplish the fast, accurate, sensitive and selective measurements. As a continuation of this work, another enzyme, homocysteine α,γ‐lyase, was used and the parallel experiments of using both enzymes were carried out against the effect of pH, sensitivity, linearity, and interferences, in an intended comparison between these two enzymes. The excellent linearity of amperometric currents against homocysteine concentrations, high sensitivities and low detection limits for both enzymes reconfirmed that the electrochemical method is superior over other analytical means. The high enzymatic activity of methionine α,γ‐lyase surpassing homocysteine α,γ‐lyase endowed the former higher sensitivity, lower detection limit and faster response than the latter, suggesting methionine α,γ‐lyase a better candidate for homocysteine measurement by electrochemical method. The differences between these two enzymes on the trends of response time and sensitivity at different pH environments, reactivity toward several forms of homocysteine as well as on the interference from several agents were also addressed and discussed.     

Low-frequency Raman spectra of odd α,ω-disubstituted n-alkanes

Low-Frequency Raman spectra of odd α,ω-dibromo- and α,ω-dihydroxy-n-alkanes were recorded. The longitudinal acoustic mode (LAM-1) frequencies were assigned by references to the published results for n-alkanes and even α,ω-disubstituted n-alkanes and also by taking account of the effects of end intermolecular forces and end-group masses by use of the chain model of Minoni and Zerbi.     

A Mild Isomerization Reaction for β,γ‐Unsaturated Ketone to α,β‐Unsaturated Ketone

A series of β,γ‐unsaturated ketones were isomerized to their corresponding α,β‐unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo‐cyclic double bond (β,γ‐position) on ketone was rearranged to exo‐cyclic double bond (α,β‐position) under the reaction conditions.     

Synthesis of halogenated monodispersed telechelic oligomers. III. Bistelomerization of allyl acetate with telogens which exhibit α, ω-di(trichloromethyled) end groups

The redox bistelomerization of allyl acetate with telogens which exhibit α, ω-di(trichloromethyled) end groups catalyzed by copper, iron salts, or a ruthenium complex led to monoadducts and telechelic oligomers. These diacetates were quantitatively changed into diols. Such compounds have been characterized by both ¹H- and ¹³C-NMR. A reactivity series has been determined and shows that both end groups must be activated to obtain the expected telechelic products in satisfactory yields.     

Synthesis of new optically active α,α′,β‐trisubstituted‐β‐lactones as monomers for stereoregular biopolyesters

Various optically active (4R)‐alkyloxycarbonyl‐3,3‐dialkyl‐2‐oxetanones as monomers were synthesized from L‐(S)‐malic acid in six steps to prepare a new family of stereopolyesters for biomedical applications. The synthesis began with an esterification followed of a dialkylation in the aim to introduce hydrophobic groups as methyl or reactive group as allyl. Then, a saponification has permitted to obtain the corresponding diacids that reacted with appropriate alcohols to furnish different monoesters. The last and most important step was activation of hydroxyl group of monoesters with the asymmetric carbon configuration inversion according to the Mitsunobu reaction. Thus, this reaction has provided lactones from monoesters with 100% enantiomeric excess which was confirmed by ¹H NMR and by the synthesis of corresponding isotactic and semicrystalline homopolyesters. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2586–2597     

Synthesis of α,β-unsaturated ketone from α-iodo ketone using photoirradiation

Irradiation of α-iodo ketone in hexane under a nitrogen atmosphere with a high-pressure mercury lamp (λ>300nm) at room temperature afforded the corresponding α,β-unsaturated ketones in good yield. This reaction affords a new, clean and convenient synthetic method for the α,β-unsaturated ketone.     

Preparation of poly(alkylenebenzimidazole) by ruthenium complex catalyzed polycondensation of 3,3′‐diaminobenzidine with α,ω‐diols

The reactions of 3,3′‐diaminobenzidine with 1,12‐dodecanediol in 1 : 1–1:3 molar ratios in the presence of RuCl₂(PPh₃)₃ catalyst give poly(alkylenebenzimidazole), [ (CH₂)₁₁ O (CH₂)₁₁ Im / (CH₂)₁₀ Im ]_n (Im: 5,5′‐dibenzimidazole‐2,2′‐diyl) (I_a‐I_d) in 71–92% yields. The relative ratio between the [(CH₂)₁₁ O (CH₂)₁₁ Im ] unit (A) and the [‐ (CH₂)₁₀ Im ] unit (B) in the polymer chain varies depending on the ratio of the substrates used. The polymer I_a obtained from the 1 : 3 reaction contains these structural units in a 98 : 2 ratio. The polymers are soluble in polar solvents such as DMF (N,N‐dimethylformamide), DMSO (dimethyl sulfoxide), and NMP (N‐methyl‐2‐pyrrolidone) and have molecular weights M_n (M_w) of 4,200–4,800 (4,800–6,500) by GPC (polystyrene standard). The polymerization of the diol and 3,3′‐diaminobenzidine in higher molar ratios leads to partial cross‐linking of the resulting polymers I_e and I_f via condensation of imidazole NH group with CH₂OH group. Similar reactions of 3,3′‐diaminobenzidine with α,ω‐diols, HO(CH₂)_mOH (m = 4–10), in a 1 : 3 molar ratio give the polymers containing [ (CH₂)_m−1 O (CH₂) _m−1 Im ] and [ (CH₂) _m−2 Im ] units with partial cross‐linked structures. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1383–1392, 1999     

Regioselective hydrosilations. I. The hydrosilation of α,ω-dihydrogen functional oligopolydimethylsiloxanes with 3-vinyl-7-oxabicyclo[4.1.0]heptane

The hydrosilation of α,ω-dihydrogen functional oligopolydimethylsiloxanes with epoxy compounds containing vinyl groups has been found to take place regioselectively in such a manner that compounds can be isolated in high yields in which only one Si? H group has been reacted. Three different α,ω-dihydrogen functional oligopolydimethysiloxanes with different chain lengths were monohydrosilated and the resulting epoxide monomers characterized. The rate of hydrosilation at the first Si? H functional group has been shown to be considerably faster than at the second site and from these kinetic studies, activation energies for each hydrosilation step were calculated. Mechanisms are considered which offer an explantion for these observations. © 1993 John Wiley & Sons, Inc.     

Synthesis of Aryl α,α-Difluoroalkyl Ketones as Potent Inhibitors of Cholesterol Esterase

Aryl α,α-difluoroalkyl ketones were synthesized from the reaction of ethyl α,α-difluoroacylate with aryl lithium at ?78°C or from the coupling of aryl iododifluoromethyl ketone with 1-alkene in the presence of tetcrakis(triphenylphosphine)palladium(0). These compounds were potent inhibitors of pancreatic cholesterol esterase with K_i values in the range 15 μM-20 nM.     

Studies on the Mass Spectra of N‐Aryl α,β‐Unsaturated γ‐Lactams

The mass spectra of a series of N‐aryl α,β‐unsaturated γ‐lactams were studied. Besides the molecular ion, the three characteristic fragments such as [M⁺‐29], [M⁺‐55], and [M⁺‐82] were commonly found in a series of N‐Aryl α,β‐unsaturated γ‐lactams in EI/MS. Further more the mechanism for the interpretation of these fragments is also de scribed.     

Photoinduced transformation of α,β-epoxyketones to β-hydroxyketones by Hantzsch 1,4-dihydropyridine

Irradiation (λ >300 nm) of Hantzsch 1,4-dihydropyridine with aromatic α,β-epoxyketones in acetonitrile selectively breaks the Cα---O bond of the epoxides giving the corresponding β-hydroxyketones in excellent yields.     

A Novel Method for the Synthesis of α,β‐Unsaturated Amides Mediated by Samarium Diiodide

Promoted by Samarium diiodide (SmI₂), α,β‐unsaturated amides were formed from nitrogen anions (formed in situ by the reduction of nitro compounds) and α,β‐unsaturated esters. This reaction contrasts with the conjugate addition between amines and α,β‐unsaturated esters promoted by samarium triiodide (SmI₃) and provides an alternative attractive way to obtain α,β‐unsaturated amides using SmI₂.     

Design and Synthesis of α,β‐Epoxyketones as New Anticancer Agents

As epoxy functional group has high anticancer activity, α,β‐epoxyketones were designed and synthesized as new anticancer agents, and their structures were confirmed by UV, ¹H NMR, IR, MS technigeces and elemental analysis. Their in vitro anticancer activities were evaluated by MTT method and the results showed that the compound 4c exhibited good activity with IC₅₀ of 17.8, 22.0 and 24.1 µg/mL against A‐549, Hela and HepG2 cells, respectively. The dose of LD50 of the mice by intragastric administration was 1864.4 mg/kg. Therefore, the α,β‐epoxyketones could potentially provide as new anticancer agents.     

Ultrasound Promoted 1, 3-Dipolar Cycloaddition Reactions of Nitrile Oxides with α, β-Unsaturated Acetals

The 1,3-dipolar cycloaddition reactions of nitrile oxides and α,β-unsaturated 1,3-dioxolanes were effectively accelerated by ultrasound irradiation to give the A²-isoxazolines with yields and regioselectivities surpassing those of the corresponding thermal reactions.     

1,4-Conjugate addition of allyltrimethylsilane to α,β-unsaturated ketones

α,β-Unsaturated ketones smoothly undergo conjugate addition with allyltrimethylsilane in the presence of a catalytic amount of elemental iodine under very mild and convenient conditions to afford the corresponding Michael adducts in high yields with high selectivity.     

Oxidative acylation of α,α‐diarylallylic alcohols: Synthesis of 1,2,4‐triarylbutane‐1,4‐diones

A metal‐free mediated oxidative acylation of α,α‐diarylallylic alcohols with simple aromatic aldehydes for the synthesis of 1,2,4‐triphenylbutane‐1,4‐diones is presented. In the presence of TBPB (tert‐butyl peroxybenzoate), desired products were obtained in good to excellent yields for 28 examples. This protocol features high regioselectivity, wide functional group tolerance and atom economy.     

Highly Enantioselective Iridium‐Catalyzed Hydrogenation of α,β‐Unsaturated Esters

α,β‐Unsaturated esters have been employed as substrates in iridium‐catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic‐ and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals.