Alkene Moiety Research Articles

Characterization and Fate of a Septanosyl Ferrier Cation in the Gas and Solution Phases.

Ferrier reactions follow a mechanistic pathway whereby Lewis acid activation of a cyclic enol ether facilitates departure of an allylic leaving group to form a glycosyl Ferrier cation. Attack on the Ferrier cation provides a new acetal linkage concurrent with the transposition of the alkene moiety. The idiosyncratic outcomes of Ferrier reactions of seven-membered ring carbohydrate-based oxepines prompted an investigation of its corresponding septanosyl Ferrier cation. Experiments that characterized the ion, including gas-phase cryogenic IR spectroscopy matched with density functional theory-calculated spectra of candidate cation structures, as well as product analysis from solution-phase Ferrier reactions, are reported here. Results from both approaches revealed an inclination of the seven-membered ring cation to contract to five-membered ring structures. Gas-phase IR spectra matched best to calculated spectra of structures in which five-membered dioxolenium formation opened the oxepine ring. In the solution phase, an attack on the ion by water led to an acyclic enal that cyclized to a C-methylene-aldehydo arabinofuranoside species. Attack by allyl trimethylsilane, on the other hand, was diastereoselective and yielded a C-allyl septanoside.

Synthesis of Selectively gem-Difluorinated Molecules; Chiral gem-Difluorocyclopropanes via Chemo-Enzymatic Reaction and gem-Difluorinated Compounds via Radical Reaction.

The incorporation of fluorine atoms into an organic compound can alter the chemical reactivity or biological activity of the resulting compound due to the strong electron withdrawing nature of the fluorine atom. We have synthesized many original gem-difluorinated compounds and described the results in four sections. The first section describes the synthesis of optically active-gem-difluorocyclopropanes via the chemo-enzymatic reaction; we applied these compounds to liquid crystalline molecules, then further discovered a potent DNA cleavage activity for the gem-difluorocyclopropane derivatives. The second section describes the synthesis of selectively gem-difluorinated compounds via a radical reaction; we synthesized fluorinated analogues of a sex pheromone of the male African sugarcane borer, Eldana saccharina, and used the compounds as proof for investigating the origin of pheromone molecule recognition on the receptor protein. The third involves the synthesis of 2,2-difluorinated-esters by visible light-driven radical addition of 2,2-difluoroacetate with alkenes or alkynes in the presence of an organic pigment. The last section describes the synthesis of gem-difluorinated compounds via the ring-opening of gem-difluorocyclopropanes. We further developed a novel method of synthesizing gem-difluorohomoallylic alcohols via the ring-opening of gem-difluorocyclopropane and aerobic oxidation by photo-irradiation in the presence of an organic pigment. Since gem-difluorinated compounds that were prepared by the present method have two olefinic moieties with a different reactivity at the terminal position, we accomplished the synthesis of four types of gem-difluorinated cyclic alkenols via the ring-closing-metathesis (RCM) reaction.

Photochemical diastereoselective synthesis and spectral characterization of (E)-3-(2-benzoylstyryl)-4H-chromen-4-ones

An efficient, concise, and green photochemical vinylogous aldol reaction for the diastereoselective synthesis of novel trans-3-(2-benzoylstyryl)-4H-chromen-4-ones starting from readily available methylbenzophenone and 3-formylchromone in the absence of any bases, metals, or other catalysts is described. The products could be obtained under UV LED (365 nm) irradiation at room temperature in 9 h with perfect diastereoselectivity. To discuss the special patterns of alkene protons, to identify its trans-conformation and verify the two trans-alkene protons (β-H and γ-H), NMR spectra analysis (1D-NMR and 2D-NMR) was conducted in details by the chemical shifts, couplings and correlations. Single crystal X-ray analysis confirmed the trans-conformation and all the compounds were unequivocally confirmed by NMR, HRMS and XRD analysis. XRD analysis of 3a further aids to disclose the reason why the alkene moiety presented a better planarity than that of benzophenone moiety of the title compounds.

Palladium-Catalyzed Hydrocarbonylative Spirolactonization for Expedite Construction of Oxaspirolactones.

A novel palladium-catalyzed cascade hydrocarbonylation of the alkene moiety followed by intramolecular spirolactonization of 2-vinylaryl hydroxyalkyl ketones has been developed, which offers efficient and expedited access to furnishing oxaspirolactones in high yields with high chemoselectivities. This new method is compatible with an array of functional groups and proceeds under mild reaction conditions with commercially available catalyst components.

Quercetin and resveratrol inhibit ferroptosis independently of Nrf2-ARE activation in mouse hippocampal HT22cells.

Oxidative stress is the central pathomechanism in multiple cell death pathways, including ferroptosis, a form of iron-dependent programmed cell death. Various phytochemicals, which include the inducers of the nuclear factor erythroid-2-related factor 2-antioxidant response element (Nrf2-ARE) transcription pathway, prevent ferroptosis. We recently reported that several compounds, such as the potent Nrf2-ARE inducer curcumin, protect mouse hippocampus-derived HT22cells against ferroptosis independently of Nrf2-ARE activity. The present study characterized the anti-ferroptotic mechanisms of two additional Nrf2-ARE inducers, quercetin and resveratrol. Both compounds prevented erastin- and RSL3-induced ferroptosis of wild-type HT22cells, and also blocked the exacerbated erastin- and RSL3-induced ferroptosis of Nrf2-knockdown HT22cells. In both HT22cells, quercetin and resveratrol blocked erastin- and RSL3-induced elevation in reactive oxygen species. These results suggest that the Nrf2-ARE pathway does protect against ferroptosis, but quercetin and resveratrol act by reducing oxidative stress independently of Nrf2-ARE induction. Quercetin and resveratrol also reduced Fe2+ concentrations in HT22cells and in cell-free reactions. Thus, quercetin and resveratrol likely protect against erastin- and RSL3-induced ferroptosis by inhibiting the iron-catalyzed generation of hydroxyl radicals. Unlike quercetin, resveratrol cannot form a chelate structure with Fe2+ but the density functional theory computation demonstrates that resveratrol can form stable monodentate complexes with the alkene moiety and the electron-rich A ring.

Catalytic Arylalkylation of Alkenyl Amines at Remote Sites via Directed Nickel Catalysis

Comprehensive SummaryDirecting group‐assisted, transition metal‐catalyzed three‐component difunctionalization of alkenes has emerged as a powerful tool to drive molecular complexity. However, this strategy generally works with the substrates bearing directing groups in close proximity to the alkene moieties, due to the preference for formation of kinetically stable five‐membered metallacycles. Herein, we have disclosed a complementary strategy to accomplish a nickel‐catalyzed remote arylalkylation of alkenyl amines with excellent regioselectivity and diastereofidelity, involving rare six‐ or seven‐membered metallacycles. This general protocol is compatible with a series of δ‐ and ε‐alkenyl amines, providing corresponding valuable δ,ε‐ and ε,ζ‐difunctionalized aliphatic amines that would be difficult to synthesize. The coordination of the bidentate picolinamide auxiliary and the facile oxidative addition of alkyl halides to Ni(I) species are the key to the success of the developed remote olefin dicarbofunctionalization.

Oxidation of Monoterpenes to Form Diols and Triols: A Versatile Toolbox for Polymer Synthesis

AbstractPolyols and polyacrylates have a wide range of applications in polymer synthesis as monomers, initiators, or building blocks in a variety of polymerization reaction types. With an ever‐growing need to reduce the global dependency on fossil fuels, finding bio‐based/renewable sources for these compounds is now critical. Herein, the alkene moieties of common, abundant terpenes are functionalized via oxidation to expand the “toolbox” of bio‐based diols and triols. These polyol compounds are readily converted into the corresponding terpene‐derived diacrylates using mild conditions. As a proof of concept, it is demonstrated that these monomers can be used in aza‐Michael polymerizations, forming new (bio)degradable poly‐β‐amino esters.

Pd(0)-Catalyzed Asymmetric 7-Endo Hydroacyloxylative Cyclization of 1,6-Enyne Enabled by an Anion Ligand-Directed Strategy.

Despite diversity in reaction mechanisms, the palladium-catalyzed cyclization of 1,6-enyne generally proceeds in a 5-exo manner. Herein, we report the development of a Pd(0)-catalyzed hydroacyloxylative cyclization of 1,6-enyne in either 7-endo-trig or 6-exo-trig fashion when paired with an appropriate dihaloacetic acid reactant, such as F2HCCO2H and Cl2HCCO2H. Using the combination of Pd2(dba)3 and a chiral phosphine ligand, the hydroacyloxylative cyclization of 1,6-enyne bearing a 1,1-disubstituted alkene moiety readily gives highly enantiopure seven-membered heterocycles while the reaction of those having a 1,2-disubstituted alkene affords six-membered rings with moderate enantioselectivity. Preliminary experimental studies suggest a reaction mechanism featuring an unusual E-to-Z vinyl-Pd(II) isomerization and alkene trans-oxypalladation, which is proven to be governed by the rationally selected carboxylate.

Copper(I)-Catalyzed Regio- and Stereoselective Silaboration of Terminal Allenes.

Organic compounds bearing both silyl and boryl groups are important building blocks in organic synthesis because of the adequate reactivity of the silyl and boryl groups and high stereospecificity in their derivatization reactions. The difference in reactivity between the silyl and boryl groups enables stepwise derivatization of these groups to afford complex molecules. Here, we report the copper(I)-catalyzed silaboration of terminal allenes to produce multisubstituted allylic boronates embedded with an alkenyl silane structure. The reaction can proceed with a variety of allenes and silylboranes. Furthermore, the silyl and boryl groups were successfully converted into other functional groups, while retaining the stereochemistry of the alkene moiety.

Full theoretical protocol for the design of metal-free organic electron donor-spacer-acceptor systems.

A user-friendly (time-dependent) density functional theory based algorithm is proposed to design new donor-spacer-acceptor systems for electron transfer reactions. This algorithm is focused on metal-free organic compounds, most of which contain aromatic or alkene moieties. The oxidation and reduction potentials are calculated, together with the excited-state energy difference including the zero-point energy and the structural properties required to calculate an electron transfer Gibbs free energy change. The proposed algorithm has been tested on well-known systems, while two new compounds are suggested for photoinduced intramolecular electron transfer reactions using this scheme. The methodology here presented is intended to be a tool for synthetic physical-chemists, allowing them to evaluate the properties of hypothetical systems before the synthesis, enabling the study of limitless combinations of donor-spacer-acceptor arrangements.

Construction of gel networksvia[2+2] photocycloaddition

Cross-linking of olefin moieties in branched polymers could furnish gel networksvia[2+2] photocycloadditions. And the obtained networks are reversible and self-healing, which show promising applications in biology and biomedical science.

Citronella-based polyesters by organocatalyzed ring-opening polymerization and their recyclable crosslinked films

Independence of food supply chain is a grand challenge encountered by the development of bio-based polymers. Here, we demonstrate the synthesis of amorphous aliphatic polyesters via organocatalyzed ring-opening polymerization of 9-membered lactone monomer, a novel downstream product of non-edible citronella oil. In particular, chemical transformation of trisubstituted alkene moiety owned by this renewable biomass was achieved by cross-metathesis of this bulky group with methyl acrylate. Three-armed star polymers were converted to free-standing films by UV-induced crosslinking. In particular, these crosslinked thin films could be efficiently recycled as ω-hydroxy ester upon methanolysis. This work opens a new avenue for the synthesis and application of terpene- and terpenoid-based polymers.

Stereoselective Domino Heck‐Suzuki Reactions

AbstractPalladium catalysis enables efficient and versatile domino reactions that are initiated by an intramolecular Mizoroki‐Heck reaction and then terminated by a Suzuki‐Miyaura coupling. The stereochemistry of this cascade is concerned under three aspects: Firstly, as stereoselective formation of carbon−carbon‐double bonds, when the initial carbometalation occurs at an alkyne moiety. Secondly as diastereoselective and thirdly enantioselective formation of stereogenic carbon centers when the intramolecular Heck step is directed to an alkene moiety. Valuable protocols lead to – otherwise not easily accomplished – stereo control in the formation of tri‐ and tetra‐substituted double bonds according to the first conception. The diastereoselective versions permit the formation of multiple stereocenters in mono‐ and polycycles. Enantioselective protocols were developed only recently. The fact that the newly created stereocenters are highly‐substituted, tertiary or quaternary ones, makes the methods that are presented in this review useful and versatile tools in synthesis.

Synthesis of 1,3-Dioxan-2-ones by Photo-Aerobic Selenium-π-Acid Multicatalysis.

An expedient method for the synthesis of cyclic carbonates from homoallylic carbonic acid esters by means of photo-aerobic selenium-π-acid multicatalysis is reported. Until now, conceptually related methods commonly relied either on the stoichiometric addition of electrophiles onto the substrate's alkene moiety or the presence of pre-installed leaving groups in allylic position of said alkene to - in part, catalytically - initiate an intramolecular attack by an adjacent carbonic acid ester group. In sharp contrast, the current study shows that the C-C double bond of homoallylic carbonic acid esters can be directly activated by the catalytic interplay of a pyrylium dye and a diselane using ambient air as the sole oxidant and visible light as an energy source.

Construction of the [7–5–5] Tricyclic Core of Daphniphyllum Alkaloids via a Cationic Cascade Reaction

The [7-5-5] tricyclic core of daphniphyllum alkaloids, containing contiguous stereogenic centers at C14 and C15 and a tetrasubstituted alkene moiety between C9 and C10, was constructed via a cascade reaction that involved an electrocyclic reaction of a pentadienyl cation and intramolecular interception of the resultant cyclopentenyl cation.

Green production of biologically active Ag and Ag–Cu nanoparticles from Prosopis cineraria pod waste extract and their application in epoxidation

The main focus of the current research is bio-nano-technologically produced nanoparticles (NPs) utilizing waste materials. There is a need for developing advanced technology to reduce waste in an eco-friendly way. Therefore, presently the discarded aqueous portion of Prosopis cineraria pod was used after boiling, to synthesize Ag and Ag–Cu NPs. FT-IR spectra illustrated the presence of phenyl propenoids and flavonoids displaying capping as well as reducing properties. TEM and SEM imaging exhibited an average size of Ag NPs (14 nm) and Ag–Cu NPs (27 nm). The crystallinity nature was confirmed by XRD, and the Cu in Ag–Cu NPs was validated through energy-dispersive X-ray analysis. According to the antimicrobial data, Saccharomyces cerevisiae displayed a zone of inhibition (ZOI) of 42.85% (Ag NPs) and 33.98% (Ag–Cu NPs) at lower concentrations (0.0321 mg/ml), while Bacillus subtilis was found most susceptible (85% ZOI) to Ag NPs at 0.5 mg/ml concentration. Further, these NPs (Ag and Ag–Cu) were utilized in the epoxidation of alkene moieties. Ag NPs showed lower conversion (65%), while Ag–Cu NPs were very active for epoxidation of linalool (93% conversion), suggesting the presence of Cu-facilitated epoxidation. To the best of our knowledge for the first time, aqueous waste is applied to prepare green NPs that can be used as antimicrobial agents and in the synthesis of platform chemicals (epoxide) for industrial aspects. These inexpensive ways of producing green NPs have been utilized several times and have found potential applications in nano-medicine, therapeutics, and modification of monoterpenoids to fine fragrance.

Substrate-Dependent Selectivity in Sc(OTf)3-Catalyzed Cyclization of Alkenoic Acids and N-Protected Alkenamides

Five- and six-membered ring lactones and lactams are ubiquitous frameworks in various natural and synthetic molecules and are key building blocks in organic synthesis. Catalytic addition of an O-H or N-H bond across an unactivated C–C double bond is an appealing approach to rapidly access such highly valuable N- and O-containing skeletons in a waste-free and 100% atom efficient process. Herein, we report, for the first time, the efficient and high-yield cyclization of δ/ε-alkenoic acids and N-protected δ-alkenamides catalyzedby practical and easily accessible Lewis acid scandium(III) triflate under thermal and microwave conditions. The selectivity outcome of the reaction of δ/ε-alkenoic acids was dependent on the substitution patterns of the backbone chain and alkene moiety, leading to the exclusive formation of either the corresponding γ/δ-lactones via an O-selective cyclization or the Friedel–Crafts-type product by C-selective cyclization. An uncommon and rarely disclosed O-selective cyclization occurred preferentially or exclusively when N-protected δ-alkenamides were engaged in the reaction. The atom selectivity of the cyclization was unambiguously confirmed by single crystal X-ray crystallography.

Silver Dependent Enantiodivergent Gold(I) Catalysed Asymmetric Intramolecular Hydroamination of Alkenes: A Theoretical Study

We report a theoretical study of the first silver-dependent enantiodivergent gold-catalysed reaction. The combination of a single chiral binuclear gold(I) chloride complex and silver perchlorate catalyses the asymmetric intramolecular hydroamination of alkenes and affords both enantiomers of the products by applying a simple solvent change from toluene to methanol. A gold-silver chloride adduct that occurs only in methanol appears to control the enantioinversion. If one gold atom coordinates and activates the alkene moiety, the other gold is included in an adduct with silver chloride, which coordinates a methanol solvent molecule and further interacts with the amine function. If the use of toluene implies free anions and affords (S)-enantiomer, methanol allows a proximal interaction with the amine, leads to an opposite stereodifferentiation of the two diastereomeric intermediates during the final protodeauration step and results in the (R)-enantiomer.

A Tandem Prins/Friedel‐Crafts Cyclization Strategy for the Stereoselective Synthesis of Hexahydro‐2H‐benzo[g]chromenes

AbstractA tandem Prins/Friedel‐Crafts cascade strategy has been developed for the synthesis of hexahydro‐2H‐benzo[g]chromene derivatives. Under action of equimolecular amount of BF3 etherate, δ,ϵ‐unsaturated alcohols and arylacetaldehydes are coupled to form oxocarbenium ion intermediates, which are captured by the alkene moiety through a favored six‐membered transition state. The Prins‐cyclization resultant tertiary carbenium ions undergo consecutive intramolecular Friedel–Crafts cyclization to create the tricyclic products. This process enables a tandem formation of three new chemical bonds in one single operation with high yields and stereoselectivity in most cases. When cyclic substituents are involved, a variety of spiro derivatives could also be synthesized successfully, which further proved the robustness of this methodology.

Nonconventional Fluorescent Hyperbranched Polymer Dots as Skin Nanocarriers Constructed from an Olefinic Aliphatic AB2-Type Monomer

We constructed an olefinic aliphatic AB2 monomer (π-AB2) for the synthesis of a nonconventional fluorescent hyperbranched polymers (π-HBPs) through self-polymerization. We obtained π-AB2 from N-(3-aminopropyl)diethanolamine and maleic anhydride in three steps with a total yield of 79%. The π-HBPs possessed hyperbranched poly(amido acid) structures with internal alkene moieties, branched amino groups, and carboxyl terminal units. With their nonconjugated hyperbranched structures, the π-HBPs functioned as water-soluble polymer dots. Inter- and intramolecular hydrogen bonding in the π-HBPs resulted in a physically cross-linked structures displaying nonconventional fluorescence. This fluorescence arose from spatial conjugation at the molecular level, leading to clustering-induced emission with the lone pairs of electrons and the π-electrons interacting in a narrow confinement space. The emission of π-HBP 03 occurred at 460 nm upon excitation of 390 nm, with quantum yields of 13.5 and 7.5% at pH 7 and 3, respectively. From an examination of the relationship between chemical structure and photoluminescence, we found that the fluorescence emissions of the HBP without internal alkene moieties and π-HBP 03 (with internal alkene moieties) were 395 and 460 nm, respectively (a red-shift of 65 nm when removing the olefinic units). The self-assembly of π-HBP 03 in aqueous solution produced nanosized (ca. 9.1 nm) particles, as determined through dynamic light scattering. π-HBP 03 is noncytotoxic, with a cell viability of >90% at 1500 μg mL–1. When applied to percutaneous absorption mouse skin, the penetration ability of the π-HBPs increased in various time profiles according to the cluster size and nanostructure of the polymer dots. When we incubated HaCaT cells with π-HBP 03 for 24 h, confocal microscopy revealed that π-HBP 03 became located within the cells. Furthermore, assays revealed that π-HBP 03 displayed effective antioxidant abilities when employed at concentrations of 0.6 and 1.5 mg mL–1.