scholarly journals Electrochemical Corey–Winter reaction. Reduction of thiocarbonates in aqueous methanol media and application to the synthesis of a naturally occurring α-pyrone

2018 ◽  
Vol 14 ◽  
pp. 547-552 ◽  
Author(s):  
Ernesto Emmanuel López-López ◽  
José Alvano Pérez-Bautista ◽  
Fernando Sartillo-Piscil ◽  
Bernardo A Frontana-Uribe
Keyword(s):  
Room Temperature ◽  
Supporting Electrolyte ◽  
Trichoderma Viride ◽  
Chemical Yield ◽  
Vitreous Carbon ◽  
Aqueous Methanol ◽  
High Chemical ◽  
Naturally Occurring ◽  
Divided Cell ◽  
Stereo Selectivity

An electrochemical version of the Corey–Winter reaction was developed giving excellent results in aqueous methanol media (MeOH/H2O (80:20) with AcOH/AcONa buffer 0.5 M as supporting electrolyte), using a reticulated vitreous carbon as cathode in a divided cell. The electrochemical version is much more environmentally friendly than the classical reaction, where a large excess of trialkyl phosphite as reducing agent and high temperatures are required. Thus, cathodic reduction at room temperature of two cyclic thiocarbonates (−1.2 to −1.4 V vs Ag/AgCl) afforded the corresponding alkenes, trans-6-(pent-1-enyl)-α-pyrone and trans-6-(pent-1,4-dienyl)-α-pyrone, which are naturally occurring metabolites isolated from Trichoderma viride and Penicillium, in high chemical yield and with excellent stereo selectivity.

Room Temperature Flow Electrochemistry as a Means of Retaining the “Memory of Chirality” via Hofer Moest Type Reaction

2020 ◽  
Author(s):  
Tomas Hardwick ◽  
Rossana Cicala ◽  
Nisar Ahmed
Keyword(s):  
Continuous Flow ◽  
Room Temperature ◽  
Biological Activities ◽  
Supporting Electrolyte ◽  
Enantiomeric Excess ◽  
Flow Chemistry ◽  
Batch Processes ◽  
Enabling Technology ◽  
Chiral Compounds ◽  
Memory Of Chirality

<p>Many chiral compounds have become of great interest to the pharmaceutical industry as they possess various biological activities. Concurrently, the concept of “memory of chirality” has been proven as a powerful tool in asymmetric synthesis, while flow chemistry has begun its rise as a new enabling technology to add to the ever increasing arsenal of techniques available to the modern day chemist. Here, we have employed a new simple electrochemical microreactor design to oxidise an L-proline derivative at room temperature in continuous flow. Flow performed in microreactors offers up a number of benefits allowing reactions to be performed in a more convenient and safer manner, and even allow electrochemical reactions to take place without a supporting electrolyte due to a very short interelectrode distance. By the comparison of electrochemical oxidations in batch and flow we have found that continuous flow is able to outperform its batch counterpart, producing a good yield (71%) and a better enantiomeric excess (64%) than batch with a 98% conversion. We have, therefore, provided evidence that continuous flow chemistry has the potential to act as a new enabling technology to replace some aspects of conventional batch processes. </p>

Naturally Occurring Organic Acid-catalyzed Facile Diastereoselective Synthesis of Biologically Active (E)-3-(arylimino)indolin-2-one Derivatives in Water at Room Temperature

2019 ◽  
Vol 23 (16) ◽  
pp. 1778-1788 ◽  
Author(s):  
Gurpreet Kaur ◽  
Arvind Singh ◽  
Kiran Bala ◽  
Mamta Devi ◽  
Anjana Kumari ◽  
...  
Keyword(s):  
Room Temperature ◽  
Biologically Active ◽  
Environmentally Benign ◽  
Diastereoselective Synthesis ◽  
Substituted Anilines ◽  
Reaction Conditions ◽  
Naturally Occurring ◽  
Acid Catalyzed ◽  
Reaction Media ◽  
Column Chromatographic

A simple, straightforward and efficient method has been developed for the synthesis of (E)-3-(arylimino)indolin-2-one derivatives and (E)-2-((4-methoxyphenyl)imino)- acenaphthylen-1(2H)-one. The synthesis of these biologically-significant scaffolds was achieved from the reactions of various substituted anilines and isatins or acenaphthaquinone, respectively, using commercially available, environmentally benign and naturally occurring organic acids such as mandelic acid or itaconic acid as catalyst in aqueous medium at room temperature. Mild reaction conditions, energy efficiency, good to excellent yields, environmentally benign conditions, easy isolation of products, no need of column chromatographic separation and the reusability of reaction media are some of the significant features of the present protocol.

scholarly journals Mercury or Mercury Free Restorations in Oral Cavity

2018 ◽  
Vol 7 (3) ◽  
pp. 201
Author(s):  
Rakesh Kumar Yadav ◽  
Umesh Pratap Verma ◽  
Rini Tiwari ◽  
Akhilanand Chaurasia
Keyword(s):  
European Union ◽  
Alloy Powder ◽  
Room Temperature ◽  
Composite Resin ◽  
Dental Amalgam ◽  
Filling Material ◽  
Tooth Structure ◽  
Naturally Occurring ◽  
Gallium Alloys ◽  
Amalgam Fillings

<span>Amalgam is basically a concoction of metals that has been used as a potent filling material in dentistry for the last 150 years. Amalgam usually consists of silver, mercury, tin and copper. Dental amalgam is a material used to fill cavities of tooth. Over the years, amalgam has become a topic of concern because it contains mercury. Mercury is a naturally occurring metal in the environment. Mercury exists as a liquid in room temperature but when heated, it becomes a gas. Flexibility of amalgam as a filling material is due Mercury. An alloy powder, a compound that is soft in nature when mixed with mercury makes it enough to mix and condense into the tooth. It hardens quickly and offers strong resistance to the forces of biting and chewing. There are studies reported on the safety of amalgam fillings. In 2005, European Union launched a comprehensive mercury strategy to reduce use of mercury. In 2008, countries like Norway and Denmark restricted the use of dental amalgam containing mercury. In 2009, this research was evaluated by U.S. Food and Drug Administration (FDA) and found no rationale to limit the use of amalgam.  There are certain restorative materials that are available commercially that are mercury free in nature like Gold, Porcelain, Gallium alloys, Composite resin restoratives etc. They offer many advantages over amalgams containing mercury like: seals the dentin from future decay, reinforces remaining tooth structure, provides smooth and bonded margins, conservative and it blends naturally.</span>

scholarly journals Synthesis of Some 2-Amino-5-substituted-1,3,4-oxadiazole Derivatives in the Acetic Acid

2011 ◽  
Vol 8 (s1) ◽  
pp. S448-S454 ◽  
Author(s):  
Sanjeev Kumar
Keyword(s):  
Acetic Acid ◽  
Room Temperature ◽  
Platinum Electrode ◽  
Supporting Electrolyte ◽  
Saturated Calomel Electrode ◽  
Reference Electrode ◽  
Lithium Perchlorate ◽  
Environmentally Benign ◽  
Controlled Potential ◽  
Oxadiazole Derivatives

An environmentally benign method for the preparation of 2-amino-5-substituted-1,3,4-oxadiazoles (1a-n) at platinum electrode through the electrooxidation of semicarbazone at room temperature is reported. The electrolysis were carried out at controlled potential in acetic acid solvent using lithium perchlorate as supporting electrolyte in an undivided cell assembly. Square shaped plates of platinum were used for working as well as counter electrode and a third electrode saturated calomel electrode was used as a reference electrode for the measurement of potential difference between two electrodes during the electrolysis.

Synthesis of nitropolychlorinated dibenzo-p-dioxins (NPCDDs) and their photochemical reaction with nucleophiles

1995 ◽  
Vol 73 (6) ◽  
pp. 826-834 ◽  
Author(s):  
Simona G. Merica ◽  
Nigel J. Bunce
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Linear Relationship ◽  
Nitro Group ◽  
Photochemical Reaction ◽  
Ring Opening ◽  
Sodium Ethoxide ◽  
Chemical Yield ◽  
Triplet Excited State ◽  
High Chemical

A series of nitropolychlorodibenzo-p-dioxins (NPCDDs) was synthesized by condensation between catechols and 2,6-dinitrohalobenzene derivatives. In the presence of sodium ethoxide in anhydrous ethanol, these underwent photochemical SN2Ar* substitutions meta to the nitro group in high chemical yield and moderate quantum yield. Both ring-opening and chloride replacement reactions were observed. The reactions involved the triplet excited state of the NPCDD, and showed a linear relationship between Φ−1 and [nucleophile]−1. Analogous reactions with KCN in methanol showed similar behaviour, but the products could not be isolated. Keywords: photosubstitution, SN2Ar*, dibenzo-p-dioxins.

scholarly journals EKSPLORASI SPATIAL DAN IDENTIFIKASI CENDAWAN ENDOFIT PADA TANAMAN KAKAO (Theobroma cacao L.) DI BALI

2018 ◽  
pp. 1
Author(s):  
Lilis Riana Tambunan ◽  
Meitini Proborini ◽  
Putu Adriani Astiti
Keyword(s):  
Endophytic Fungi ◽  
Theobroma Cacao ◽  
Room Temperature ◽  
Trichoderma Viride ◽  
Raw Material ◽  
Rhizopus Stolonifer ◽  
Pharmaceutical Industries ◽  
Soil Rhizosphere ◽  
The Village ◽  
Theobroma Cacao L

Cocoa plant (Theobroma cacao L.) can grow well in the highlands and lowlands, a plantation and industrial plantwhich is known as one of the export commodities, as raw material for the food and pharmaceutical industries which cancontribute to an increase in foreign exchange endophytic fungus is a fungus living on a live network of plants such asseeds, leaves, flowers, twigs, stems and roots. Truffles are generally mutualistic endophyte and is known to stimulate thegrowth of plants, capable of producing antibiotics and plant growth regulators (hormones). This study aims to determinethe diversity and identify endophytic fungi on Kakao.yang found in two different locations in Bali, in the village of KajaBuahan District of Payangan, Gianyar and the Village of Tua, Marga, Tabanan regency subdistricts. Research carried outin the field with the exploration methods, isolation, identification and diversity analysis conducted at the Laboratory ofPlant Taxonomy (Mycology), Department of Biology, Faculty of Mathematics, University of Udayana. Laboratoryresearch conducted by isolating the roots, leaves, plant stems and content of the soil (rhizosphere) cocoa. Once isolated,grown on PDA medium subsequently incubated at room temperature 250C. Isolates that grow back isolated and purifiedon a PDA medium for further identified to the genera or species level. A total of six isolates of endophytic fungi identifiedin the rhizosphere and cocoa plant that is where four of these isolates were identified to species, two isolates were notidentified until genus. Fungi were identified namely Aspergillus flavus, Rhizopus stolonifer, Cladosporiumsphaeropermum, Trichoderma viride, isolates 1 and 2 isolates.Keywords: cocoa, endophytic fungi, highlands and lowlands

scholarly journals The principal magnetic susceptibilities of some paramagnetic crystals at low temperatures

1933 ◽  
Vol 140 (842) ◽  
pp. 695-713 ◽  
Keyword(s):  
Ammonium Sulphate ◽  
Low Temperatures ◽  
Room Temperature ◽  
Manganese Carbonate ◽  
Small Range ◽  
Restricted Range ◽  
Nickel Sulphate ◽  
Temperature Range ◽  
Naturally Occurring ◽  
Ferrous Carbonate

Our knowledge of the temperature variation of the principal susceptibilities of paramagnetic crystals is as yet fragmentary. The principal susceptibilities of a number of paramagnetic crystals have been determined by Finke and by Rabi at room temperature but the first measurements on orientated crystals over any range of temperature were those of Foëx. He has published the principal susceptibilities of siderose (a mineral which is mainly ferrous carbonate but which contains appreciable quantities of the carbonates of manganese and other metals) over the range 87° to 400°K. and some measurements but not actual principal susceptibilities for manganese sulphate, MnSO 4 .4H 2 O. The writer measured the principal susceptibilities of cobalt ammonium sulphate and nickel sulphate, NiSO 4 . 7H 2 O over the temperature range 14°-290°K. and the writer and de Haas have published measurements on manganese ammonium sulphate crystals over the restricted range 14°-20° K. In addition Dupouy has repeated Foëx’s observations on siderose and has measured the principal susceptibilities of dialogite (a naturally occurring manganese carbonate) and oligist (Fe 2 O 3 ), all over a small range of temperature above 0° C. Quite recently Bartlett has employed Rabi’s method to determine the principal susceptibilities of the following compounds, CoSO 4 . 7H 2 O, CoSO 4 . (NH 4 ) 2 SO 4 . 6H 2 O, CoSO 4 . K 2 SO 4 . 6H 2 O, CuSO 4 . (NH 4 ) 2 SO 4 . 6H 2 O CuSO 4 . K 2 SO 4 . 6H 2 O, NiSO 4 . (NH 4 ) 2 SO 4 . 6H 2 O over the temperature range —45° to +55°C. In the writer’s opinion, however, Bartlett’s procedure is liable to several objections.

scholarly journals Diastereoselective Cyclopropanation by Using Camphorpyrazolidinone Derived α,β-Unsaturated Amides and Ylide

2020 ◽  
Author(s):  
sudershan gondi
Keyword(s):  
Carboxylic Acid ◽  
Asymmetric Synthesis ◽  
Michael Addition ◽  
Chemical Yield ◽  
High Chemical ◽  
Unsaturated Carboxylic Acid ◽  
Optically Pure ◽  
The Michael Addition

<p><b>Abstract:</b> High to moderate diastereoselectivity and high chemical yield are observed in the Michael addition of ylide and chiral camphorpyrazolidinone ylide to an optically pure a,b-unsaturated carboxylic acid derivatives derived from a chiral camphorpyrazolidinone and a,b-unsaturated carbonyl respectively. A novel route to the asymmetric synthesis of cyclopropanation derivatives is described.</p>

Determination of Sulfites in Foods by Simultaneous Nitrogen Purging and Differential Pulse Polarography

1989 ◽  
Vol 72 (3) ◽  
pp. 476-480
Author(s):  
Walter Holak ◽  
John Specchio
Keyword(s):  
Room Temperature ◽  
Mercury Electrode ◽  
Differential Pulse ◽  
Differential Pulse Polarography ◽  
Peak Potential ◽  
Naturally Occurring ◽  
Pulse Polarography ◽  
Dropping Mercury Electrode ◽  
Improved Technique

Abstract An improved technique has been developed for determination of sulfites in food by differential pulse polarography. A Teflon™ sleeve is fitted to the dropping mercury electrode capillary so that SO2 is purged from the sample and simultaneously detected at peak potential. Bound sulfite in the sample is released at room temperature by addition of base in the absence of oxygen. For some foods, the prepared sample was passed through a Sep-Pak C-18 cartridge to remove naturally occurring sulfur compounds so that only added sulfite is measured. The level of detection was approximately 1 μg S02/g. Results agreed with those obtained by the optimized Monier- Williams method for a variety of foods.

scholarly journals Organocatalytic Asymmetric Michael Addition of Ketones to α, β-Unsaturated Nitro Compounds

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 618 ◽  
Author(s):  
Jae Ho Shim ◽  
Si Hun Nam ◽  
Byeong-Seon Kim ◽  
Deok-Chan Ha
Keyword(s):  
Michael Addition ◽  
Chemical Yield ◽  
Nitro Compounds ◽  
Neutral Condition ◽  
High Chemical ◽  
Aromatic Ketones ◽  
Michael Additions ◽  
Asymmetric Michael Addition ◽  
Neutral Conditions ◽  
Organic Catalyst

An organic catalyst “(R, R)-1,2-diphenylethylenediamine(DPEN) derivative’’ was devel-oped as a chiral bifunctional organocatalyst and applied for asymmetric Michael additions of aromatic ketones to trans-β-nitroalkene compounds under neutral conditions. The isopropyl-subs-tituted thiourea catalyst in neutral condition provides high chemical yield and enantioselectivities (ee) (up to 96% yield, 98% ee).

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