We report the development of a silicon nanowire array‐stabilized palladium nanoparticle catalyst, SiNA‐Pd. Its use in the palladium‐catalyzed Mizoroki‐Heck reaction, the hydrogenation of an alkene, ...the hydrogenolysis of nitrobenzene, the hydrosilylation of an α,β‐unsaturated ketone, and the C‐H bond functionalization reactions of thiophenes and indoles achieved a quantitative production with high reusability. The catalytic activity reached several hundred‐mol ppb of palladium, reaching a TON of 2 000 000.
An array of reactions: A silicon‐nanowire‐array‐stabilized palladium‐nanoparticle catalyst, SiNA‐Pd, was designed and used in the palladium‐catalyzed Mizoroki–Heck reaction. It can catalyze a variety of other reactions and has a high reusability.
Abstract
Background
In
Saccharomyces cerevisiae
, the retrograde signalling pathway is activated in ρ
0/−
cells, which lack mitochondrial DNA. Within this pathway, the activation of the transcription ...factor Pdr3 induces transcription of the ATP-binding cassette (ABC) transporter gene,
PDR5,
and causes pleiotropic drug resistance (PDR). Although a histone deacetylase, Rpd3, is also required for cycloheximide resistance in ρ
0/−
cells, it is currently unknown whether Rpd3 and its DNA binding partners, Ume6 and Ash1, are involved in the activation of
PDR5
transcription and PDR in ρ
0/−
cells. This study investigated the roles of
RPD3
,
UME6
, and
ASH1
in the activation of
PDR5
transcription and PDR by retrograde signalling in ρ
0
cells.
Results
ρ
0
cells in the
rpd3
∆ and
ume6
∆ strains, with the exception of the
ash1
∆ strain, were sensitive to fluconazole and cycloheximide. The
PDR5
mRNA levels in ρ
0
cells of the
rpd3
∆ and
ume6
∆ strains were significantly reduced compared to the wild-type and
ash1
∆ strain. Transcriptional expression of
PDR5
was reduced in cycloheximide-exposed and unexposed ρ
0
cells of the
ume6
∆ strain; the transcriptional positive response of
PDR5
to cycloheximide exposure was also impaired in this strain.
Conclusions
RPD3
and
UME6
are responsible for enhanced
PDR5
mRNA levels and PDR by retrograde signalling in ρ
0
cells of
S. cerevisiae
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
The performance of transition metal hydroxides, as cocatalysts for CO
2
photoreduction, is significantly limited by their inherent weaknesses of poor conductivity and stacked structure. ...Herein, we report the rational assembly of a series of transition metal hydroxides on graphene to act as a cocatalyst ensemble for efficient CO
2
photoreduction. In particular, with the Ru-dye as visible light photosensitizer, hierarchical Ni(OH)
2
nanosheet arrays-graphene (Ni(OH)
2
-GR) composites exhibit superior photoactivity and selectivity, which remarkably surpass other counterparts and most of analogous hybrid photocatalyst system. The origin of such superior performance of Ni(OH)
2
-GR is attributed to its appropriate synergy on the enhanced adsorption of CO
2
, increased active sites for CO
2
reduction and improved charge carriers separation/transfer. This work is anticipated to spur rationally designing efficient earth-abundant transition metal hydroxides-based cocatalysts on graphene and other two-dimension platforms for artificial reduction of CO
2
to solar chemicals and fuels.
Metalloenzymes are essential proteins with vital activity that promote high-efficiency enzymatic reactions. To ensure catalytic activity, stability, and reusability for safe, nontoxic, sustainable ...chemistry, and green organic synthesis, it is important to develop metalloenzyme-inspired polymer-supported metal catalysts. Here, we present a highly active, reusable, self-assembled catalyst of poly(imidazole-acrylamide) and palladium species inspired by metalloenzymes and apply our convolution methodology to the preparation of polymeric metal catalysts. Thus, a metalloenzyme-inspired polymeric imidazole Pd catalyst (MEPI-Pd) was readily prepared by the coordinative convolution of (NH4)2PdCl4 and poly(N-vinylimidazole)-co-(N-isopropylacrylamide)5 in a methanol–water solution at 80 °C for 30 min. SEM observation revealed that MEPI-Pd has a globular-aggregated, self-assembled structure. TEM observation and XPS and EDX analyses indicated that PdCl2 and Pd(0) nanoparticles were uniformly dispersed in MEPI-Pd. MEPI-Pd was utilized for the allylic arylation/alkenylation/vinylation of allylic esters and carbonates with aryl/alkenylboronic acids, vinylboronic acid esters, and tetraaryl borates. Even 0.8–40 mol ppm Pd of MEPI-Pd efficiently promoted allylic arylation/alkenylation/vinylation in alcohol and/or water with a catalytic turnover number (TON) of 20 000–1 250 000. Furthermore, MEPI-Pd efficiently promoted the Suzuki–Miyaura reaction of a variety of inactivated aryl chlorides as well as aryl bromides and iodides in water with a TON of up to 3 570 000. MEPI-Pd was reused for the allylic arylation and Suzuki–Miyaura reaction of an aryl chloride without loss of catalytic activity.
Self-assembly of copper sulfate and a poly(imidazole–acrylamide) amphiphile provided a highly active, reusable, globular, solid-phase catalyst for click chemistry. The self-assembled polymeric Cu ...catalyst was readily prepared from poly(N-isopropylacrylamide-co-N-vinylimidazole) and CuSO4 via coordinative convolution. The surface of the catalyst was covered with globular particles tens of nanometers in diameter, and those sheetlike composites were layered to build an aggregated structure. Moreover, the imidazole units in the polymeric ligand coordinate to CuSO4 to give a self-assembled, layered, polymeric copper complex. The insoluble amphiphilic polymeric imidazole Cu catalyst with even 4.5–45 mol ppm drove the Huisgen 1,3-dipolar cycloaddition of a variety of alkynes and organic azides, including the three-component cyclization of a variety of alkynes, organic halides, and sodium azide. The catalytic turnover number and frequency were up to 209000 and 6740 h–1, respectively. The catalyst was readily reused without loss of catalytic activity to give the corresponding triazoles quantitatively.
You oughta use water: Broad functional-group (FG) tolerance was observed for the title coupling of aryl halides (X=Cl, Br, I) and aryl boronic acids to give biaryl compounds with up to 94 % ee. The ...chiral imidazoindole phosphine-palladium catalyst supported on an amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG) resin could be recycled readily.
The increased demand for more efficient, safe, and green production in fine chemical and pharmaceutical industry calls for the development of continuous‐flow manufacturing, and for chiral chemicals ...in particular, enantioselective catalytic processes. In recent years, this emerging direction has received considerable attention and has seen rapid progress. In most cases, catalytic enantioselective flow processes using homogeneous, heterogeneous, or enzymatic catalysts have shown significant advantages over the conventional batch mode, such as shortened reaction times, lower catalysts loadings, and higher selectivities in addition to the normal merits of non‐enantioselective flow operations. In this Minireview, the advancements, key strategies, methods, and technologies developed the last six years as well as remaining challenges are summarized.
Going with the flow: In recent years, continuous‐flow techniques have received considerable attention and shown rapid progress in manufacturing. Among these, catalytic enantioselective flow processes using homogeneous, heterogeneous, or enzymatic catalysts have shown significant advantages over the conventional batch mode. In this Minireview, recent advances in continuous‐flow enantioselective catalysis are summarized and discussed, with emphasis on studies published after 2013.
Immobilized Pd‐catalyzed Suzuki‐Miyaura coupling under continuous‐flow conditions using a packed‐bed reactor, representing an efficient, automated, practical, and safe technology compared to ...conventional batch‐type reactions. The core objective of this study is the development of an active and durable catalyst. In contrast to supported Pd nanoparticles, the attachment of Pd complexes onto solid supports through well‐defined coordination sites is considered a favorable approach for preparing highly dispersed and stabilized Pd species. These species can be directly employed in various flow reactions without the need for pre‐treatment. This concept paper explores recent achievements involving the application of immobilized Pd complexes as precatalysts for continuous‐flow Suzuki‐Miyaura coupling. Our focus is to elucidate the significance of the designed catalyst structures in relation to their catalytic performance under flow conditions. Additionally, we highlight various reaction systems and catalyst packing methods, emphasizing their crucial roles in establishing a practical synthesis process.
The present ‘Concept’ provides a comprehensive review of recent strides in continuous‐flow Suzuki‐Miyaura coupling, employing a packed‐bed reactor featuring immobilized palladium complexes. Emphasis is placed on meticulously designed catalyst structures and the innovative reaction technologies employed under continuous‐flow conditions, accentuating their pivotal roles in the establishment of a pragmatic synthesis process.
Dental pulp stem cells (DPSCs) are mesenchymal stem cells (MSCs) that have multipotent differentiation and a self-renewal ability. They have been useful not only for dental diseases, but also for ...systemic diseases. Extensive studies have suggested that DPSCs are effective for various diseases, such as spinal cord injuries, Parkinson's disease, Alzheimer's disease, cerebral ischemia, myocardial infarction, muscular dystrophy, diabetes, liver diseases, eye diseases, immune diseases, and oral diseases. DPSCs have the potential for use in a cell-therapeutic paradigm shift to treat these diseases. It has also been reported that DPSCs have higher regenerative potential than the bone marrow-derived mesenchymal stem cells known as representative MSCs. Therefore, DPSCs have recently gathered much attention. In this review, the therapeutic potential of DPSCs, the latest progress in the pre-clinical study for treatment of these various systemic diseases, and the clinical applications of DPSCs in regenerative medicine, are all summarized. Although challenges, including mechanisms of the effects and establishment of cell processing and transplantation methods for clinical use, still remain, DPSCs could be promising stem cells sources for various clinical applications, because of their easy isolation by a noninvasive procedure without ethical concerns.
The development of highly active and reusable supported catalysts for Suzuki‐Miyaura coupling and catalytic C−H arylation is important for fundamental and applied chemistry, with these reactions ...being used to produce medical compounds and functional materials. Herein, we found that a mesoporous composite made of a linear poly(4‐vinylpyridine) and tetrachloropalladate acted as a dual‐mode catalyst for a variety of cross‐coupling reactions, with both Pd nanoparticles and a Pd complex catalyst being observed under different conditions. The polyvinylpyridine‐palladium composite 1 was readily prepared via the molecular convolution of poly(4‐vinylpyridine) and sodium tetrachloropalladate to provide a hardly soluble polymer‐metal composite. The Suzuki‐Miyaura coupling and the C−H arylation of aryl chlorides and bromides with arylboronic acids, thiophenes, furans, benzene, and anisole proceeded in the presence of 0.004 mol% (40 mol ppm) to 1 mol% Pd of 1 to afford the corresponding coupling products in high yields. Furthermore, the catalyst was reused without an appreciable loss of activity. Pharmaceutical compounds and functional materials were synthesized via the coupling reactions. N2 gas adsorption/desorption analysis indicated that the catalyst had a mesoporous nature, which played a crucial role in the catalysis. In the Suzuki‐Miyaura couplings, in situ generated palladium nanoparticles in the polymer matrix were catalytically active, while a polymeric Pd(II) complex was crucial in the C−H arylations. These catalytic species were investigated via XAFS, XPS, far‐infrared absorption, and Raman spectroscopies, as well as DFT calculations.
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