10.1021/jo00249a037
The research focused on the regioselective reactions of the 5-(ethylthio)furan-2(5H)-one anion with various electrophilic reagents. The purpose of the study was to explore the reactivity of this anion towards different electrophilic species, such as Michael acceptors, carbonyl compounds, alkyl halides, and acyl halides, with the aim of selectively forming new bonds, particularly carbon-carbon bonds, at the 3- and 5-positions of 2(5H)-furanones. The researchers used a variety of chemicals in their experiments, including 5-(ethylthio)furan-2(5H)-one, lithium diisopropylamide (LDA), potassium carbonate, propionaldehyde, acetyl chloride, ethyl chloroformate, cyclohexenone, methyl acrylate, and cyclohexanone. The conclusions drawn from the study indicated that the reactions proceeded with high regioselectivity, controlled by the nature of the electrophile, and provided a simple and mild method for the synthesis of important substituted lactones, which has wide potential utility in organic synthesis.
10.2478/s11696-013-0530-6
The research focuses on the synthesis, molecular structure, and evaluation of hemilabile imino-phosphine palladium(II) complexes in Heck reactions. The ligands 2-(diphenylphosphino)benzyl-(2-thiophene)methylimine (V) and 2-(diphenylphosphino)benzyl-(2-thiophene)ethylimine (VI) were prepared from 2-(diphenylphosphino)benzaldehyde and thiophene amines with high yields. These ligands were then reacted with PdCl2(cod) or PdClMe(cod) to form palladium(II) complexes I–IV. The molecular structure of complex II was confirmed by X-ray crystallography, revealing a distorted square planar geometry around the palladium atom. The complexes were evaluated as catalysts for the Heck coupling reactions of iodobenzene with methyl acrylate under mild conditions, showing significant activities with isolated yields of 64%, 68%, and 58% for complexes I, II, and IV, respectively. The study highlights the role of imino-phosphine ligands in enhancing catalytic activities due to their hemilabile property, which allows reversible protection of the coordination site.
10.1016/S0040-4039(01)91234-1
The study focused on the synthesis of sclerostin and enantiomers of sclerostin to determine their absolute configurations. The researchers synthesized both enantiomers from (-)-carvone using intermolecular and intramolecular Diels-Alder reactions. The key chemicals involved included (-)-carvone as a starting material, PCC-NaOAc for oxidation to form the aldehyde, methylallylmagnesium bromide for allylation, and methacrylate for the Diels-Alder reaction. The study identified (4R, 9R, 10R)-(+)-sclerostin and (4R, 9R, 10R)-(-)-sclerostin as natural enantiomers by bioassay and CD spectral comparison. The spectral data of the synthesized sclerostin and sclerostin were exactly the same as those of the authentic samples, and the study found that (+)-sclerostin had strong sporulation activity, while (-)-sclerostin only showed weak activity.
10.1016/j.tetasy.2007.02.023
The research investigates the asymmetric Michael reaction to develop a method for synthesizing chiral b-ketophosphonates, which are valuable precursors for b-amino and b-hydroxy-phosphonates and have biological significance. The study focuses on using chiral b-enaminophosphonates derived from (S)-1-phenylethylamine and various electrophilic alkenes to achieve b,b-disubstituted ketophosphonates with high enantioselectivity and good yields. Key chemicals involved include the non-commercial b-ketophosphonate precursors 3a–3d, which were synthesized through a series of reactions involving hydrazones, Arbuzov reactions, and deprotection steps. The enaminophosphonates 4a–4d were then reacted with Michael acceptors such as phenylvinylsulfone and methyl acrylate. The study concludes that the asymmetric Michael reaction on acyclic enaminophosphonate compounds with non-substituted Michael acceptors is feasible, yielding chiral b-ketophosphonates with high enantiomeric excesses, similar to acyclic enaminoester derivatives. The introduction of dibenzyl- or diphenyl-phosphonate groups, however, decreased reactivity and enantioselectivity compared to diethylphosphonate groups. The absolute configurations of the adducts were determined using vibrational circular dichroism (VCD) due to challenges in obtaining single-crystal samples for X-ray analysis. Future work aims to extend this reaction to substituted Michael acceptors.
10.1016/j.jorganchem.2007.10.015
The research focuses on the synthesis and characterization of new bridging aminoallylidene complexes through Olefin–aminocarbyne coupling in diiron and diruthenium complexes. The study explores the reaction of bridging aminocarbyne complexes with olefins such as acrylonitrile, methyl acrylate, styrene, and diethyl maleate, in the presence of Me3NO and NaH. These reactions yield the corresponding l-allylidene complexes, which are characterized by various analytical techniques including infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis. The research also investigates further modifications of the bridging ligand through methylation and protonation reactions, as well as the potential for coordination with additional metal complexes through the nitrile functionality. The experiments involve the preparation of intermediate nitrile complexes and the formation of cationic complexes, with the structures of some compounds confirmed through X-ray diffraction studies. The research provides insights into the regio- and stereospecificity of the coupling reactions and the flexibility of the dinuclear M2(CO)2(Cp)2 frame in accommodating different bridging organic molecules.
10.1016/S0040-4020(01)97207-2
The research investigates the use of 2-pyridineseleninic anhydride as an efficient reagent for converting olefins to unsaturated ketones while retaining the original position of the double bond. This reagent is more reactive towards olefins than benzeneseleninic anhydride. The study was inspired by the observation that the model alkyl-2’-pyridylselenide underwent allylic oxidation by 2-pyridineseleninic anhydride generated in situ from the oxidation of dipyridyldiselenide with iodoxybenzene. The researchers tested this hypothesis using various model olefins and found that 2-pyridineseleninic anhydride, conveniently introduced as 2,2’-dipyridyldiselenide, effectively catalyzed the allylic oxidation of olefins to ketones. The study also explored the use of m-iodoxybenzoic acid and iodosobenzene as oxidants and demonstrated the system's effectiveness on various substrates, including cholesteryl benzoate and geraniol acetate. The research highlights the potential of this new allylic oxidation system based on an organoselenium catalyst for clean and selective oxidation of olefins without the need for aqueous work-up.
10.1246/cl.1988.1567
The research investigates palladium-catalyzed reactions of neopentylidenesiliranes with various unsaturated compounds. The study focuses on how the nature of ligands on palladium influences the ring expansion products obtained. Key chemicals involved include 1,1-dimesityl-2-Z-neopentylidenesilirane and its E-isomer, which serve as the main reactants. Dimethyl acetylenedicarboxylate, acetylene, t-butylallene, and methyl acrylate are among the unsaturated compounds that react with the neopentylidenesiliranes to produce different adducts. Palladium complexes, such as Pd(PPh3)4 and Pd(II) complexes with varying ligands, act as catalysts to facilitate these reactions. The products formed, like insertion product 3 and trace amount of 4, are analyzed through techniques like NMR, mass spectra, and elemental analysis to confirm their structures. The research highlights the unusual ring expansion reaction modes and the role of reactants in activating the catalyst, as well as the influence of steric and electronic factors on the reaction pathways and product formation.
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