A palladium‐catalyzed enantioselective intramolecular σ‐bond cross‐exchange between C−I and C−C bonds is realized, providing chiral indanones bearing an alkyl iodide group and an all‐carbon ...quaternary stereocenter. Pd/TADDOL‐derived phosphoramidite is found to be an efficient catalytic system for both C−C bond cleavage and alkyl iodide reductive elimination. In addition to aryl iodides, aryl bromides can also be used for this transformation in the presence of KI. Density‐functional theory (DFT) calculation studies support the ring‐opening of cyclobutanones occuring through an oxidative addition/reductive elimination process involving PdIV species.
In exchange: An enantioselective cross‐exchange between C−I and C−C bonds is realized by palladium‐catalyzed sequential oxidative addition and reductive elimination. Chiral indanones bearing an alkyl iodide group and an all‐carbon quaternary stereocenter are synthesized in good yields and enantioselectivities.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Two natural biomass derivatives i.e., tannic acid (TA) and phosphorylated-cellulose nanofibrils (P-CNFs) were employed to decorate graphene oxide network and the as-prepared flame-retardant GTP paper ...with ultrasensitive fire alarm response can be applied as desirable smart fire alarm sensor material.
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•Biomass-derivatives decorated graphene oxide networks were fabricated via a facile strategy.•The synergistic reinforcing effect was formed in the hybrid networks based on bionic design.•The bio-based hybrid networks showed excellent flame resistance and structural stability.•Ultrasensitive fire alarm time of < 1 s and desirable fire early warning responses were achieved.•Such hybrid networks can be used as sustainable fireproof and fire alarm sensor materials.
Effective utilization of natural biomass-derivatives for developing sustainable, mechanically robust, and fireproof materials remains a huge challenge in fire safety and prevention field. Herein, based on bionic design, the hybrid interconnected networks composed of two-dimensional (2D) graphene oxide (GO) nanosheets, renewable one-dimensional (1D) phosphorylated-cellulose nanofibrils (P-CNFs) and tannic acid molecules (TA) were prepared via a green and facile evaporation-induced self-assembly strategy. Through construction of the multiple synergistic interactions among the TA, P-CNFs and GO, the optimized 1D/2D interconnected networks with hierarchical nacre-like structure were achieved and exhibited improved mechanical properties (tensile strength and Young’s modulus up to ∼ 132 MPa and ∼ 7 GPa, i.e. ∼ 3.6 and ∼ 14 times higher than that of the pure GO paper), good structural stability in various environments (aqueous solutions with different pH values), excellent flame retardancy (keeping structural integrity after flame attack), and ultrasensitive fire alarm functions (e.g., ultrafast flame alarm time of < 1 s and sensitive fire warning responses). Further, such 1D/2D interconnected networks can act as effective flame-retardant nanocoatings to significantly improve the flame retardancy of combustible PU foam materials (e.g., ∼48% decrease in peak heat release rate at only 10 wt% content). Based on the structure observation and analysis, the related synergistic reinforcing and flame-retardant mechanisms were proposed and clarified. Clearly, this work provides a new route for design and development of environmentally friendly fireproof and fire alarm materials based on utilization of natural biomass-derivatives.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A palladium‐catalyzed enantioselective sequential ring‐opening/cross‐coupling of cyclobutanones is disclosed that provides chiral indanones bearing C3‐quaternary stereocenters. The reaction process ...involves palladium‐catalyzed nucleophilic addition of cyclobutanones and aryl halides, enantioselective β‐carbon elimination, and intermolecular trapping of a transient σ‐alkylpalladium complex with boronic acids. Alternatively, an intramolecular cyclopropanation is realized through C−H bond functionalization in the absence of external coupling reagents, affording chiral cyclopropane‐fused‐indanones in good yields and enantioselectivity.
Enantioselective desymmetrization of prochiral cyclobutanones was realized through tandem palladium‐catalyzed ring‐opening/cyclopropanation to provide chiral cyclopropane‐fused indanones. With external coupling reagents, the transient σ‐alkylpalladium intermediate can be captured to afford an array of chiral indanones bearing C3‐quaternary stereocenters.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Highlights
Graphene oxide-based hybrid networks were fabricated via introducing multi-amino molecule with triple roles (i.e., cross-linker, fire retardant and reducing agent).
The optimized hybrid ...network with mechanically robust, exceptional intumescent effect and ultra-sensitive fire alarm response (~ 0.6 s) can be used as desirable smart fire alarm sensor materials.
Exceptional fire shielding performances, e.g., ~ 60% reduction in peak heat release rate and limiting oxygen index of ~ 36.5%, are achieved, when coated such hybrid network onto combustible polymer foam.
Smart fire alarm sensor (FAS) materials with mechanically robust, excellent flame retardancy as well as ultra-sensitive temperature-responsive capability are highly attractive platforms for fire safety application. However, most reported FAS materials can hardly provide sensitive, continuous and reliable alarm signal output due to their undesirable temperature-responsive, flame-resistant and mechanical performances. To overcome these hurdles, herein, we utilize the multi-amino molecule, named HCPA, that can serve as triple-roles including cross-linker, fire retardant and reducing agent for decorating graphene oxide (GO) sheets and obtaining the GO/HCPA hybrid networks. Benefiting from the formation of multi-interactions in hybrid network, the optimized GO/HCPA network exhibits significant increment in mechanical strength, e.g., tensile strength and toughness increase of ~ 2.3 and ~ 5.7 times, respectively, compared to the control one. More importantly, based on P and N doping and promoting thermal reduction effect on GO network, the excellent flame retardancy (withstanding ~ 1200 °C flame attack), ultra-fast fire alarm response time (~ 0.6 s) and ultra-long alarming period (> 600 s) are obtained, representing the best comprehensive performance of GO-based FAS counterparts. Furthermore, based on GO/HCPA network, the fireproof coating is constructed and applied in polymer foam and exhibited exceptional fire shielding performance. This work provides a new idea for designing and fabricating desirable FAS materials and fireproof coatings.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The Sonogashira-type cross-coupling reaction is one of the most significant alkynylation transformations in organic chemistry. However, highly enantioselective alkynylation
via
the Sonogashira-type ...cross-coupling reaction is rather limited, mainly due to the difficulties in matching the stereoselective induction of chiral ligands with the combinational behavior of Pd/Cu-based bimetallic catalysts. We herein report novel enantioselective palladium/copper-catalyzed alkyl alkynylation of cyclobutanones with terminal alkynes
via
tandem C-C bond activation/Sonogashira-type cross coupling reaction, in which a novel chiral TADDOL-derived phosphoramidite ligand bearing fluorine and silicon-based bulky groups simplified as TFSi-Phos is found to be an efficient ligand for both C(sp
2
)-C(sp
3
) bond cleavage and new C(sp
3
)-C(sp) bond formation. A wide range of chiral alkynylated indanones bearing an all-carbon quaternary stereocenter are obtained efficiently with up to 97.5 : 2.5 er.
A highly enantioselective Pd/Cu-catalyzed tandem C-C bond activation/Sonogashira reaction was developed with the aid of new TFSi-Phos, which provided chiral alkynyl indanones in good yields and enantioselectivities.
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IJS, KILJ, NUK, UL, UM, UPUK
A graphene oxide (GO)-based smart fire alarm sensor (FAS) has gained rapidly increasing research interest in fire safety fields recently. However, it still remains a huge challenge to obtain ...desirable GO-based FAS materials with integrated performances of mechanical flexibility/robustness, harsh environment-tolerance, high-temperature resistance, and reliable fire warning and protection. In this work, based on bionic design, the supermolecule melamine diborate (M·2B) was combined with GO nanosheets to form supramolecular cross-linking nanosystems, and the corresponding GO-M·2B (GO/MB) hybrid papers with a nacre-like micro/nano structure were successfully fabricated via a gel-dry method. The optimized GO/MB paper exhibits enhanced mechanical properties, e.g., tensile strength and toughness up to ∼122 MPa and ∼1.72 MJ/m3, respectively, which is ∼3.5 and ∼6.6 times higher than those of the GO paper. Besides, it also shows excellent structural stability even under acid/alkaline solution immersion and water bath ultrasonication conditions. Furthermore, due to the presence of promoting reduction effect and atom doping reactions in GO network, the resulting GO/MB network displays exceptional high-temperature resistance, sensitive fire alarm response (∼0.72 s), and ultralong alarming time (>1200 s), showing promising fire safety and protection application prospects as desirable FAS and fire shielding material with excellent comprehensive performances. Therefore, this work provides inspiration for the design and fabrication of high-performance GO-based smart materials that combine fire shielding and alarm functions.
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IJS, KILJ, NUK, PNG, UL, UM
A facile synthesis of γ,δ‐unsaturated ketones via palladium‐catalyzed ring‐opening of 2‐alkylidenecyclobutanols with organic halides is described. The key step involves Csp3
−Csp2
bond cleavage via ...palladium‐catalyzed β‐carbon elimination. The desired γ,δ‐unsaturated ketones are obtained in good to excellent yields and broad functional group tolerability. Aryl, heteroaryl, benzyl, and alkynyl halides all readily participate to forge tri‐substituted carbon‐carbon double bond in a stereoselective manner.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
An atom‐economical strategy for the synthesis of functionalized alkylidenecyclobutanes (ACBs) via Lewis acid‐catalyzed yne‐carbonyl metathesis of ynamides and cyclobutanones is described. This ...strategy features mild reaction conditions, ready availability of starting materials, and broad functional group tolerability. Furthermore, the imide group is easily converted to acid, ester, and amide, thus providing an efficient access to various functionalized ACBs.
An atom‐economical strategy for the synthesis of functionalized alkylidenecyclobutanes (ACBs) via Lewis acid‐catalyzed yne‐carbonyl metathesis of ynamides and cyclobutanones is described.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A palladium‐catalyzed enantioselective intramolecular σ‐bond cross‐exchange between C−I and C−C bonds is realized, providing chiral indanones bearing an alkyl iodide group and an all‐carbon ...quaternary stereocenter. Pd/TADDOL‐derived phosphoramidite is found to be an efficient catalytic system for both C−C bond cleavage and alkyl iodide reductive elimination. In addition to aryl iodides, aryl bromides can also be used for this transformation in the presence of KI. Density‐functional theory (DFT) calculation studies support the ring‐opening of cyclobutanones occuring through an oxidative addition/reductive elimination process involving PdIV species.
Im Austausch: Ein enantioselektiver Kreuzaustausch zwischen C‐I‐und C‐C‐Bindungen gelingt durch Palladium‐katalysierte sequentielle oxidative Addition und reduktive Eliminierung. Chirale Indanone, die eine Alkyliodidgruppe und ein quartäres Kohlenstoff‐Stereozentrum tragen, werden mit guten Ausbeuten und Enantioselektivitäten synthetisiert.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A palladium‐catalyzed enantioselective sequential ring‐opening/cross‐coupling of cyclobutanones is disclosed that provides chiral indanones bearing C3‐quaternary stereocenters. The reaction process ...involves palladium‐catalyzed nucleophilic addition of cyclobutanones and aryl halides, enantioselective β‐carbon elimination, and intermolecular trapping of a transient σ‐alkylpalladium complex with boronic acids. Alternatively, an intramolecular cyclopropanation is realized through C−H bond functionalization in the absence of external coupling reagents, affording chiral cyclopropane‐fused‐indanones in good yields and enantioselectivity.
Enantioselektive Desymmetrisierung prochiraler Cyclobutanone gelang durch eine Tandemreaktion aus Pd‐katalysierter Ringöffnung und Cyclopropanierung unter Bildung chiraler Cyclopropan‐ anellierter Indanone. Mit externen Kupplungsreagentien kann das transiente σ‐Alkylpalladium‐Intermediat abgefangen werden, wobei eine Reihe chiraler Indanone mit C3‐quartären Stereozentren entsteht.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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