An Efficient One-Pot Synthesis Of Dialkyl 3H-Naphtho[2,1,b]pyran-2,3-dicarboxylates Mediated by Vinyl Triphenylphosphonium Salt∗

Protonation of the reactive intermediates produced in the reaction between dialkyl acetylenedicarboxylates and triphenylphosphine by 2-hydroxy-1-naphthaldehyde leads to vinyltriphenylphosphonium salts, which undergo intramolecular Wittig reaction to produce dialkyl 3H-naphtho[2,1-b]pyran-2,3-dicarboxylates in fairly high yields.

     

PPh3-KOBut–Mediated Cyclization Reaction of β-Ketoesters with Alkynyl Ketones: Synthesis of Functionalized 2-Pyrones

Cyclization of alkynyl ketones with β-ketoesters mediated by PPh₃ and KOBu^t to synthesize 2-pyrone derivatives was systematically described. A variety of β-ketoesters reacted with alkynyl ketones to give functionalized 2-pyrones in moderate to good yields under mild conditions.      

Vinyl Triflate–Aldehyde Reductive Coupling–Redox Isomerization Mediated by Formate: Rhodium-Catalyzed Ketone Synthesis in the Absence of Stoichiometric Metals

Direct conversion of aldehydes to ketones is achieved via rhodium-catalyzed vinyl triflate-aldehyde reductive coupling-redox isomerization mediated by potassium formate. This method circumvents premetalated C-nucleophiles and discrete redox manipulations typically required to form ketones from aldehydes.     

Synthesis of Vinyl and β-Phthalimido Ketones

Vinyl ketones are prepared by reaction of an aldehyde with a vinyl Grignard reagent followed by a Swern oxidation. β-Phthalimido ketones are then obtained by 1,4-addition of phthalimide.     

Facile Synthesis of 4‐Functionalized Cyclopentenones

1-8-Diazabicyclo[5.4.0]undec-7-ene(DBU)‐catalyzed Michael addition of nitroalkanes to dicyclopentadienone (1) followed by flash vacuum pyrolysis (FVP) provided a high‐yielding synthesis of extremely pure 4‐nitroalkyl cyclopentenones (3). The optimized Nef reaction of the nitro adducts (2) provided 4‐ketoalkyl cyclopentenones (5) in the similar way.     

Synthesis of α-Branched Enones via Chloroacylation of Terminal Alkenes

Here, we show the conversion of unactivated alkenes into α-branched enones via regioselective chloroacylation with acyl chlorides. The method relies upon the initial in situ generation of chlorine radicals directly from the acyl chloride precursor under cooperative nickel/photoredox catalysis. Subsequent HCl elimination provides enones and α,β-unsaturated esters that are not accessible via the conventional acylation approaches that provide the other, linear constitutional isomer.     

Selenium Dioxide–Mediated Synthesis of Fused 1,2,4-Triazoles as Cytotoxic Agents

A series of fused 1,2,4-triazoles has been prepared by oxidative intramolecular cyclization of heterocyclic hydrazones with selenium dioxide. General applicability of this practical protocol was confirmed by the synthesis of moderate to good yields of 1,2,4-triazolo[4,3-a]pyridines, 1,2,4-triazolo[4,3-a]pyrimidines, 1,2,4-triazolo[4,3-a]pyramidines, and 1,2,4-triazolo-[4,3-a]quinoxa lines. All compounds were tested in vitro for their cytotoxic activity against HCT-116, A549, and Colo-205 cell lines. Two compounds, 3-(4-methoxyphenyl)-7-methyl-[1,2,4]triazolo[4,3-a]pyridine and 1-(4-methoxyphenyl)-[1,2,4]triazolo[4,3-a]quinoxaline, showed potent antiproliferative activity against the three cell lines.     

β-Cyclodextrin Mediated Synthesis of Syndiotactic-rich Polystyrene

Stereoregular polystyrene (PS) was prepared using various molarequivalents of -cyclodextrin (-CD) by polymerisingstyrene in the presence of -CD. Stereoregular (isotactic,atactic and syndiotactic) distributions of the preparedpolystyrene polymers were determined from terminal modelBernoullian statistics using ¹³C NMR data. Inclusioncomplexation of styrene by -cyclodextrin was detected byUV-Visible spectroscopy, which gave a binding constant value of31606 ± 3350 M^-1 for the 1 : 1 complex. With anincrease in the styrene : -CD ratios, the proportionof syndiotactic polymers increased. The glass transitiontemperature (T_g) of the polymer also increased along withmelting temperature (T_m) at higher styrene : -CDratios. In addition, the molecular weight of the polymers prepareddecreased with increase in the -CD concentration.     

Single-Pot Synthesis of Spiroannulated Dihydrofurans by Iodine–Ammonium Acetate–Mediated Reaction of Dimedone with Aldehydes

Iodine–ammonium acetate–mediated annealation of dimedone with aldehydes led to facile formation of spirodihydrofuran in good yields through tandem Knoevenagel–Michael iodonation and cyclodehydroiodonation reactions in a single pot.     

Synthesis and Catalytic Applications of Sulfonic Acid Group–Functionalized Nano- and Microsilica Structures

Sulfonic acid group–functionalized nano- and microsilica with different sizes and shapes were synthesized. Silica nanospheres with an average size of 225 nm, silica microtubes, and fine silica gel were prepared and functionalized by sulfonic acid. Their catalytic activity was investigated in the three-component Biginelli reaction for the synthesis of dihydropyrimidinones.     

Synthesis of Novel Oxime Functionalized Aldol Products via Michael Addition of Oximes Onto Baylis–Hillman Adducts

Triphenylphosphine‐catalyzed Michael addition of oximes 2 onto Baylis–Hillman (B‐H) adducts 1 led to an easy access to a novel class of oxime functionalized aldol products 3. This demonstrates the first use of an oxygen‐centered nucleophile in Michael addition to B‐H adducts, without touching any other functional group. Deprotection of oxime in 3 was further demonstrated using molecular hydrogen (1 atm) and 10% Pd/C (cat.) to furnish functionalized 1,3‐diols 4 as potentially useful synthons with optional backbone choice (R³ and EWG).     

Solid-phase Synthesis of Vinyl Sulfones Using Polystyrene-supported Selenomethyl Phenyl Sulfone

The solid-phase preparation of vinyl sulfones via a novel polystyrene-supported selenomethyl phenyl sulfone reagent has been reported.     

Facile Synthesis of Functionalized Bis(arylethynyl)benzene Derivatives via Sila–Sonogashira Reaction

This article describes a facile synthesis of a new series of symmetrical bis(arylethynyl)benzene derivatives via a one-pot coupling reaction between trialkylsilyl protected arylalkynyes and aryldihalides bearing both electron-withdrawing (EW) and electron-donating groups (ED) in the presence of PdCl₂(PPh₃)₂(5%) / CuI/tetrabutylammonium fluoride / triethylamine / tetrahydrofuran (sila–Sonogashira reaction) at room temperature.     

o-Iodoxy Benzoic Acid–Mediated Synthesis of 3,5-Diarylisoxazoles and Isoxazole-3-carboxylic Acids

A new, convenient, ecofriendly synthesis of 3,5-diarylisoxazoles is reported from α,β-unsaturated ketoximes. Similarly, a novel synthesis of isoxazole carboxylic acids is also reported. Both the methods use efficient, environmentally friendly, and nontoxic iodoxybenzoic acid (IBX) as an oxidative cyclizing reagent. Easy procedure, environmentally benign reaction conditions, and nontoxicity are advantages to the methodology.     

Synthesis and Fungicidal Activities of Pyrimethanil Heterocyclic Acid Salt

Seven pyrimethanil salts were synthesized by organic base containing nitrogen atom reacting with substituted pyridine acids. They are reported for the first time. Their structures have been confirmed by IR, ^1H NMR and elemental analysis. The preliminary toxicity tests indicated that most of them exhibited excellent fungicidal activities. The relationship between the structures and the fungicidal activities of the compounds was discussed.     

β-Cyclodextrin Mediated Synthesis of Sterically Controlled Styrene-acrylonitrile Copolymer

Sterically controlled styrene-acrylonitrile (SAN)copolymers were prepared by inclusion polymerizationusing molar equivalents of -cyclodextrin(-CD) and its derivative. Comonomercompositions, reactivity ratios, monomer sequence andaverage styrene and acrylonitrile sequence lengthswere determined using ¹³C NMR spectroscopy. Themolecular weight of the polymers prepared increasedwith decreasing -CD concentration, but wasfound to be less than the control. With increase inthe styrene: -CD ratios the averageacrylonitrile sequence length and run number of thepolymers increased. The glass transition temperature(_g) also increased along with the meltingtemperature (_m) of the polymers at higherstyrene:-CD ratios.     

Synthesis, Characterization and Properties of Tri-substitute Potassium Salt of Trinitrophloroglucinol

The title complex [K3（TNPG）·（H2O）2]n was synthesized by the reaction of the aqueous solutions of trinitrophlomglucinol （TNPG） with KHCO3. The complex was characterized by elemental analysis and FTIR spectroscopy, and its single crystal structure was determined by X-ray diffraction analysis. The structural analysis demonstrates that two different coordination modes of K cations [K（1） and K（2）] are around TNPG^3- anions in complex [Ka（TNPG）·（H2O）2]n, where the coordination numbers are eight. All K atoms coordinate with O atoms of phenolic hydroxyl group and nitro-group simultaneously. The thermolysis of the [Ka（TNPG） · （H2O）2]n has been investigated by using differential scanning calorimetry （DSC） and thermogravimetry-derivative thermogravimetry （TG-DTG） at a heating rate of 10 ℃/min. The thermal decomposition processes of the title complex were comprised of one endothermic dehydration stage and one exothermic decomposition stage in 270-320℃, and the final decomposition residue contained KNC. Impact and friction sensitivity results of the complex revealed its sensitive nature towards mechanical stimuli. The experiments verified that the complex has some characteristics of explosive.     

Synthesis of [5,6-3H](+/−) Gamma Vinyl GABA

Abstract

An efficient synthesis of [5,6-³H] (+/?) gamma vinyl GABA 5 from 4-aminohex-5-ynoic acid 3 is described.     

Trichloroisocyanuric Acid–Mediated One-Pot Synthesis of Unsymmetrical 2,5-Disubstituted 1,3,4-Oxadiazoles at Ambient Temperature

An efficient method for the one-pot synthesis of unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles has been developed using trichloroisocyanuric acid (TCCA) at ambient temperature. A wide variety of aromatic as well as heterocyclic aldehydes exhibit condensation with a variety of acylhydrazines followed by oxidative cyclization to yield corresponding unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles. The mild nature of the synthesis and short reaction time are notable advantages of the developed protocol.