scholarly journals Access to P-stereogenic compounds via desymmetrizing enantioselective bromination

2021 ◽  
Author(s):  
Qiu-Hong Huang ◽  
Qian-Yi Zhou ◽  
Chen Yang ◽  
Li Chen ◽  
Jin-Pei Cheng ◽  
...  
Keyword(s):  
Phosphine Oxides ◽  
Highly Efficient ◽  
Wide Range ◽  
High Yields

A highly efficient desymmetrizing asymmetric bromination of bisphenol phosphine oxides was developed, providing a wide range of chiral bisphenol phosphine oxides and bisphenol phosphinates with high yields and enantioselectivities.

Efficient Synthesis of Diaryl Sulfides by Copper-catalysed Coupling of Aryl Halides and Thioacetate in Water

2013 ◽  
Vol 37 (1) ◽  
pp. 19-21 ◽  
Author(s):  
Yimin Zhang ◽  
Iiu ◽  
Junmin Chen
Keyword(s):  
Functional Groups ◽  
Catalytic System ◽  
Aryl Halides ◽  
Efficient Synthesis ◽  
Highly Efficient ◽  
Wide Range ◽  
High Yields

A simple economical, and highly efficient catalytic system for the synthesis of diaryl sulfides by a copper-catalysed coupling of aryl halides and thioacetate in water has been developed. A variety of aryl halides reacted with thioacetate to give the desired products in high yields up to 95%. The present catalysis protocol tolerated a wide range of functional groups, including amino, fluoro, and carboxyl moieties.

Stereospecific, Palladium-catalyzed C(sp3)–H Alkenylation and Alkynylation of a Proline Derivative Enabled by 8-Aminoquinoline as a Directing Group

2020 ◽  
Author(s):  
Aleksandra Balliu ◽  
Aaltje Roelofje Femmigje Strijker ◽  
Michael Oschmann ◽  
Monireh Pourghasemi Lati ◽  
Oscar Verho
Keyword(s):  
Carboxylic Acid ◽  
Building Blocks ◽  
Wide Range ◽  
Palladium Catalyzed ◽  
Directing Group ◽  
High Yields ◽  
Vinyl Iodides ◽  
Initial Results

<p>In this preprint, we present our initial results concerning a stereospecific Pd-catalyzed protocol for the C3 alkenylation and alkynylation of a proline derivative carrying the well utilized 8‑aminoquinoline directing group. Efficient C–H alkenylation was achieved with a wide range of vinyl iodides bearing different aliphatic, aromatic and heteroaromatic substituents, to furnish the corresponding C3 alkenylated products in good to high yields. In addition, we were able show that this protocol can also be used to install an alkynyl group into the pyrrolidine scaffold, when a TIPS-protected alkynyl bromide was used as the reaction partner. Furthermore, two different methods for the removal of the 8-aminoquinoline auxiliary are reported, which can enable access to both <i>cis</i>- and <i>trans</i>-configured carboxylic acid building blocks from the C–H alkenylation products.</p>

Synthetic and Mechanistic Studies of a Versatile Heteroaryl Thioether Directing Group for Pd(II) Catalysis

2019 ◽  
Author(s):  
Andrew Romine ◽  
Kin Yang ◽  
Malkanthi Karunananda ◽  
Jason Chen ◽  
Keary Engle
Keyword(s):  
Mechanistic Studies ◽  
Salvianolic Acid ◽  
Wide Range ◽  
Computational Data ◽  
Synthetic Utility ◽  
Directing Group ◽  
High Yields ◽  
Julia Olefination ◽  
Reaction Progress Kinetic Analysis

A weakly coordinating monodentate heteroaryl thioether directing group has been developed for use in Pd(II) catalysis to orchestrate key elementary steps in the catalytic cycle that require conformational flexibility in a manner that is difficult to accomplish with traditional strongly coordinating directing groups. This benzothiazole thioether, (BT)S, directing group can be used to promote oxidative Heck reactivity of internal alkenes providing a wide range of products in moderate to high yields. To demonstrate the broad applicability of this directing group, arene C–H olefination was also successfully developed. Reaction progress kinetic analysis provides insights into the role of the directing group in each reaction, which is supplemented with computational data for the oxidative Heck reaction. Furthermore, this (BT)S directing group can be transformed into a number of synthetically useful functional groups, including a sulfone for Julia olefination, allowing it to serve as a “masked olefin” directing group in synthetic planning. In order to demonstrate this synthetic utility, natural products (+)-salvianolic acid A and salvianolic acid F are formally synthesized using the (BT)S directed C–H olefination as the key step.

Hafnium(IV) Chloride Catalyzes Highly Efficient Acetalization of Carbonyl Compounds

2019 ◽  
Vol 16 (6) ◽  
pp. 913-920 ◽  
Author(s):  
Israel Bonilla-Landa ◽  
Emizael López-Hernández ◽  
Felipe Barrera-Méndez ◽  
Nadia C. Salas ◽  
José L. Olivares-Romero
Keyword(s):  
Microwave Heating ◽  
Reaction Times ◽  
Protecting Groups ◽  
Catalyst Loading ◽  
Selective Protection ◽  
Highly Efficient ◽  
Aldehydes And Ketones ◽  
High Yields ◽  
Novel Catalyst ◽  
Acid Labile

Background: Hafnium(IV) tetrachloride efficiently catalyzes the protection of a variety of aldehydes and ketones, including benzophenone, acetophenone, and cyclohexanone, to the corresponding dimethyl acetals and 1,3-dioxolanes, under microwave heating. Substrates possessing acid-labile protecting groups (TBDPS and Boc) chemoselectively generated the corresponding acetal/ketal in excellent yields. Aim and Objective: In this study. the selective protection of aldehydes and ketones using a Hafnium(IV) chloride, which is a novel catalyst, under microwave heating was observed. Hence, it is imperative to find suitable conditions to promote the protection reaction in high yields and short reaction times. This study was undertaken not only to find a novel catalyst but also to perform the reaction with substrates bearing acid-labile protecting groups, and study the more challenging ketones as benzophenone. Materials and Methods: Using a microwave synthesis reactor Monowave 400 of Anton Paar, the protection reaction was performed on a raging temperature of 100°C ±1, a pressure of 2.9 bar, and an electric power of 50 W. More than 40 substrates have been screened and protected, not only the aldehydes were protected in high yields but also the more challenging ketones such as benzophenone were protected. All the products were purified by simple flash column chromatography, using silica gel and hexanes/ethyl acetate (90:10) as eluents. Finally, the protected substrates were characterized by NMR 1H, 13C and APCI-HRMS-QTOF. Results: Preliminary screening allowed us to find that 5 mol % of the catalyst is enough to furnish the protected aldehyde or ketone in up to 99% yield. Also it was found that substrates with a variety of substitutions on the aromatic ring (aldehyde or ketone), that include electron-withdrawing and electrondonating group, can be protected using this methodology in high yields. The more challenging cyclic ketones were also protected in up to 86% yield. It was found that trimethyl orthoformate is a very good additive to obtain the protected acetophenone. Finally, the protection of aldehydes with sensitive functional groups was performed. Indeed, it was found that substrates bearing acid labile groups such as Boc and TBDPS, chemoselectively generated the corresponding acetal/ketal compound while keeping the protective groups intact in up to 73% yield. Conclusion: Hafnium(IV) chloride as a catalyst provides a simple, highly efficient, and general chemoselective methodology for the protection of a variety of structurally diverse aldehydes and ketones. The major advantages offered by this method are: high yields, low catalyst loading, air-stability, and non-toxicity.

A highly efficient and green approach for the synthesis of pyrimido[4,5-b]quinolines using N,N-diethyl-N-sulfoethanaminium chloride

2021 ◽  
Vol 76 (2) ◽  
pp. 85-90
Author(s):  
Abdolkarim Zare ◽  
Manije Dianat
Keyword(s):  
Reaction Times ◽  
Solvent Free ◽  
One Pot ◽  
Catalyst Amount ◽  
Green Protocol ◽  
Highly Efficient ◽  
Green Approach ◽  
Solvent Free Conditions ◽  
The One ◽  
High Yields

Abstract A highly efficient and green protocol for the synthesis of pyrimido[4,5-b]quinolines has been described. The one-pot multicomponent reaction of dimedone with arylaldehydes and 6-amino-1,3-dimethyluracil in the presence of N,N-diethyl-N-sulfoethanaminium chloride ([Et3N–SO3H][Cl]) as an ionic liquid (IL) catalyst under solvent-free conditions afforded the mentioned compounds in high yields and short reaction times. Our protocol is superior to many of the reported protocols in terms of two or more of these factors: the reaction times, yields, conditions (solvent-free versus usage of organic solvents), temperature and catalyst amount.

scholarly journals A general approach to high-efficiency perovskite solar cells by any antisolvent

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Alexander D. Taylor ◽  
Qing Sun ◽  
Katelyn P. Goetz ◽  
Qingzhi An ◽  
Tim Schramm ◽  
...  
Keyword(s):  
Solar Cells ◽  
High Efficiency ◽  
Perovskite Solar Cells ◽  
Precursor Solution ◽  
Microstructural Characterization ◽  
Application Rate ◽  
Perovskite Layer ◽  
Highly Efficient ◽  
Application Procedure ◽  
Wide Range

AbstractDeposition of perovskite films by antisolvent engineering is a highly common method employed in perovskite photovoltaics research. Herein, we report on a general method that allows for the fabrication of highly efficient perovskite solar cells by any antisolvent via manipulation of the antisolvent application rate. Through detailed structural, compositional, and microstructural characterization of perovskite layers fabricated by 14 different antisolvents, we identify two key factors that influence the quality of the perovskite layer: the solubility of the organic precursors in the antisolvent and its miscibility with the host solvent(s) of the perovskite precursor solution, which combine to produce rate-dependent behavior during the antisolvent application step. Leveraging this, we produce devices with power conversion efficiencies (PCEs) that exceed 21% using a wide range of antisolvents. Moreover, we demonstrate that employing the optimal antisolvent application procedure allows for highly efficient solar cells to be fabricated from a broad range of precursor stoichiometries.

The chemistry of stabilized clusters

1982 ◽  
Vol 308 (1501) ◽  
pp. 27-34 ◽  
Keyword(s):  
Electron Donor ◽  
Organic Molecules ◽  
Metal Cluster ◽  
Organic Substrates ◽  
Insertion Reactions ◽  
Donor Ligand ◽  
Small Organic Molecules ◽  
Wide Range ◽  
Metal Metal ◽  
High Yields

Studies of the chemistry of metal cluster complexes and, in particular, their reactions with small organic molecules, have been confined to relatively few systems. Among the reasons for this are: (i) not many clusters are easily synthesized in high yields; (ii) their reactions often give a multitude of products that are difficult to separate and characterize; (iii) the conditions required to bring about reactions often lead to fragmentation of the cluster into lower nuclearity (often mononuclear) species. One cluster whose chemistry has been extensively studied is [Os 3 H 2 (CO) 10 ]. This can be synthesized in high yields from [Os 3 (CO) 12 ] + H 2 (Knox et al. 1975) and reacts readily under mild conditions with a wide range of electron-donor molecules by virtue of its coordinative unsaturation (Shapley et al. 1975; Deeming & Hasso 1976; Adams & Golembeski 1979). Formally, one may consider that a metal—metal double bond is present, which is reduced to a single bond on coordination of an additional two-electron donor ligand such as an organophosphine. The presence of metal—hydrogen bonds in this cluster and the cluster’s ability to coordinate organic substrates enable it to undergo a wide variety of insertion reactions, leading to products that may be regarded as intermediates in the reduction of organic molecules by clusters (Deeming & Hasso 1975; Keister & Shapley 1975).

Synthesis of 1,2,3–triazole compounds by click chemistry in aqueous medium and evaluation of bactericidal and antitumoral properties.

2021 ◽  
Vol 17 ◽  
Author(s):  
Lucas Lima Zanin ◽  
David Esteban Quintero Jimenez ◽  
Willian Garcia Birolli ◽  
Tiago Venâncio ◽  
Talita Alvarenga Valdes ◽  
...  
Keyword(s):  
Click Chemistry ◽  
Biological Properties ◽  
Antitumoral Activity ◽  
Biological Assays ◽  
Triazole Derivatives ◽  
Optimization Study ◽  
Water As Solvent ◽  
Wide Range ◽  
Screening Study ◽  
High Yields

Background: Triazoles are heterocyclic synthetic compounds that have gained relevance after studies by Sharpless on regioselective methodologies for the synthesis of 1,2,3-triazole derivatives. In addition, they have a wide range of biological properties. Objective: The objective of this study is to develop a synthetic methodology aligned with the principles of click chemistry for the synthesis of 1,2,3-triazole derivatives and verify the profile of these compounds in biological assays. Methods: Initially, a model reaction was selected and an optimization study involving synthetic conditions was carried out. Using the most efficient condition, a series of compounds was developed by the reactions between 2-azido-1-phenylethan-1-one derivatives and terminal alkynes. In sequence, bactericidal and antitumoral assays were performed. Results: It was possible to synthesise ten examples using water as a sustainable solvent, in 1 hour, with good yields of 73–99%, including three compounds described for the first time. Two products presented bactericidal activity, one against the gram-negative Escherichia coli ATCC 25922 and other against the gram-positive Paenibacillus alvei CBMAI 2221. Moreover, other two triazole derivatives presented antitumoral activity for prostate and pancreas cancer cells in this screening study with the bioactivity quantified for compound 1-([1,1'-biphenyl]-4-yl)-2-(4-(p-tolyl)-1H-1,2,3-triazol-1-yl)ethan-1-one (IC50 = 132 µM). Conclusion: Herein, an efficient methodology for the synthesis of 1,2,3-triazole derivatives with high yields and using water as solvent was developed. Furthermore, some compounds presented positive results to bactericidal and antitumoral assays, justifying further exploration of these novel compounds and their biological properties.

scholarly journals Growth, Phenolics, Photosynthetic Pigments, and Antioxidant Response of Two New Genotypes of Sea Asparagus (Salicornia neei Lag.) to Salinity under Greenhouse and Field Conditions

Agriculture ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 115 ◽  
Author(s):  
Manuel de Souza ◽  
Carlos Mendes ◽  
Kennia Doncato ◽  
Eliana Badiale-Furlong ◽  
César Costa
Keyword(s):  
Salt Tolerance ◽  
Antioxidant Capacity ◽  
Bioactive Compound ◽  
Antioxidant Response ◽  
Field Conditions ◽  
Carotenoid Content ◽  
Water Yield ◽  
Wide Range ◽  
Flavonoid Quercetin ◽  
High Yields

Small succulent halophytic shrubs of the genera Salicornia and Sarcocornia (Salicornioideae, Amaranthaceae) are commonly named sea asparagus and consumed worldwide as green salad in gourmet food, as conserves, and beverages. Their shoots are rich in bioactive compounds and plants show high yields in a wide range of salinities, but little is known about how salt cultivation conditions affect their chemical composition. Two genotypes (BTH1 and BTH2) of the Brazilian sea asparagus Salicornia neei Lag. were evaluated for salt tolerance and changes in shoot concentrations of organic metabolites and antioxidant activity under different salt exposure in both greenhouse and field conditions. All greenhouse plants received full strength modified Hoagland solution in deionized water with a basic electrical conductivity (EC) of 1.7 dS m−1, and with NaCl concentrations (in mM) of ~0.1 (control), 34, 86, 171, 513, and 769. After fifty days of cultivation, both S. neei genotypes showed high salt tolerance and grew better under low salinities (34–86 mM NaCl) than under control salinity. Shoots of BTH1 genotype appeared to be undergoing lignification and used their high carotenoid content to dissipate the oxidative power, and the zeaxanthin content and de-epoxidation state of xanthophylls (DES) were positively affected by salinity. Under increasing salinity, BTH2 genotype had higher relative content of chlorophyll b, which may have lowered the plant photo-oxidation rate, and increased shoot concentration of the flavonoid quercetin (up to 11.6 μg g−1 dw at 769 mM NaCl), leading to higher antioxidant capacity. In the field experiment, after 154 days of irrigation with saline (213 mM NaCl) shrimp farm effluent, BTH2 plants grew taller, produced more metabolites (e.g., total phenolics, total free flavonoids, quercetin, and protocatechuic acid) and had a greater antioxidant capacity of shoots than that of BTH1 plants and that of traditional crops irrigated with fresh water. Yield and bioactive compound composition of S. neei genotypes’ shoots can be enhanced by cultivation under moderate saline conditions.

scholarly journals Highly efficient green synthesis and photodynamic therapeutic study of hypericin and its derivatives

RSC Advances ◽  
2018 ◽  
Vol 8 (39) ◽  
pp. 21786-21792 ◽  
Author(s):  
Ying Zhang ◽  
Kun Shang ◽  
Xiaowen Wu ◽  
Siyu Song ◽  
Zebo Li ◽  
...  
Keyword(s):  
Green Synthesis ◽  
Synthetic Pathway ◽  
Highly Efficient ◽  
Therapeutic Study ◽  
High Yields ◽  
Green Conditions

A highly efficient synthetic pathway for hypericin as well as its derivatives was achieved under mild and green conditions with high yields.

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