scholarly journals Recent Developments in Weinreb Synthesis and Their Applications

2019 ◽  
Vol 35 (6) ◽  
pp. 1611-1626
Author(s):  
Maher Khalid ◽  
Shireen Mohammedand Amin Kalo
Keyword(s):  
Carboxylic Acids ◽  
Direct Conversion ◽  
Amide Group ◽  
Acid Chlorides ◽  
Organometallic Reagent ◽  
Organometallic Reagents ◽  
Weinreb Amides ◽  
Weinreb Amide ◽  
Recent Developments ◽  
High Yields

N-methoxy-N-methyl amides or Weinreb amides are worthy embranchment of amide group and their rich functional groups in organic synthesis become a strong else unfeasible conversion. Weinreb amides are produced as an intermediate product of the reaction of carboxylic acids, acid chloride or esters with organometallic reagents, which was first uncovered in 1981. The direct conversion of carboxylic acids or acid chlorides or esters to ketones or aldehydes using organometallic reagents do not lead in high yields, because the intermediate ketones are still highly reactive toward the organometallic reagent. However, after derivatization to the corresponding Weinreb Amide, reaction with organometallics does give the desired ketones, as the initial adduct is stabilized and doesn't undergo further reactions. A nucleophilic addition to the Weinreb amides results in a unique and stable five-membered cyclic tetrahedral intermediate which protects the over-addition, leading to a selective conversion.

Triethylamine borane - a stable, efficient and safe reductant for transforming carboxylic acids to primary alcohols

1990 ◽  
Vol 55 (12) ◽  
pp. 2956-2962 ◽  
Author(s):  
Otomar Kříž ◽  
Zbyněk Plzák ◽  
Jaromír Plešek
Keyword(s):  
Carboxylic Acids ◽  
Acid Chlorides ◽  
Primary Alcohols ◽  
Functional Derivatives ◽  
High Yields ◽  
Derivatives Of

Triethylamine borane, (C2H5)3N.BH3, is a stable, safe and readily available reagent which at 80 °C reduces carboxylic acids to primary alcohols in high yields; functional derivatives of carboxylic acids such as esters, nitriles or amides are virtually nonreactive with this reagent under the same conditions. Aldehydes, ketones and acid chlorides, however, react readily. No solvent is required for the process.

Exploration of Mesyl Chloride in a One Pot Conversion of Carboxylic Acids to Ketones

2020 ◽  
Vol 7 (3) ◽  
pp. 242-247
Author(s):  
Habtamu Gelaw Mekonnen ◽  
Debasis Sahoo ◽  
Samaresh Jana ◽  
Sanjoy Kumar Maji
Keyword(s):  
Carboxylic Acid ◽  
Carboxylic Acids ◽  
Functional Group ◽  
Reaction Times ◽  
Mixed Anhydride ◽  
Organometallic Reagent ◽  
Reaction Conditions ◽  
One Pot ◽  
Organometallic Reagents ◽  
Organolithium Reagents

Background: Due to the ubiquitous nature of the ketone functionality, it is considered an important functional group in organic chemistry. Hence, the synthesis of ketones from readily available starting materials is an important chemical transformation in organic synthesis. Consequently, several research efforts have been reported in the literature for the transformation of carboxylic acids to ketones in a one-pot synthesis. However, some of the procedures have limitations, such as long reaction times, harsh reaction conditions, and usage of expensive metal catalysts. Thus, a simple and convenient one-pot conversion of carboxylic acids to ketones remains desirable. Objective: We intended to develop a simple and convenient one-pot methodology for the synthesis of ketones from carboxylic acids. Our objective was to build up a carboxylic acid-based chemical template where various types of organometallic reagents can interact to produce the desired ketone. Methods: In this procedure, a carboxylic acid was converted to a mixed anhydride using mesyl chloride in the presence of a base. This mixed anhydride was then reacted with a suitable organometallic reagent at -20°C to obtain the desired ketone. The reaction was performed in a one-pot fashion. Results: Under the optimized reaction conditions, various aromatic and heteroaromatic carboxylic acids were converted to the corresponding ketones using organolithium and organomagnesium reagents with short reaction times. Moderate to good yields of the desired ketones were observed in many of these transformations. Conclusion: A simple and convenient one-pot method for the conversion of carboxylic acids to ketones has been reported. Specifically, various aromatic and `heteroaromatic carboxylic acids have been converted to the corresponding ketones in moderate to good yields. Organomagnesium and organolithium reagents were used as nucleophiles for this reaction.

Recent Developments on Synthesis of Indole Derivatives Through Green Approaches and Their Pharmaceutical Applications

2020 ◽  
Vol 24 (22) ◽  
pp. 2665-2693
Author(s):  
Dipayan Mondal ◽  
Pankaj Lal Kalar ◽  
Shivam Kori ◽  
Shovanlal Gayen ◽  
Kalpataru Das
Keyword(s):  
Biological Activities ◽  
Synthetic Methods ◽  
Pharmaceutical Chemistry ◽  
Indole Derivatives ◽  
Biological Studies ◽  
Recent Developments ◽  
Pharmaceutical Industries ◽  
Green Methodology ◽  
Conventional Methods ◽  
High Yields

Indole moiety is often found in different classes of pharmaceutically active molecules having various biological activities including anticancer, anti-viral, anti-psychotic, antihypertensive, anti-migraine, anti-arthritis and analgesic activities. Due to enormous applications of indole derivatives in pharmaceutical chemistry, a number of conventional synthetic methods as well as green methodology have been developed for their synthesis. Green methodology has many advantages including high yields, short reaction time, and inexpensive reagents, highly efficient and environmentally benign over conventional methods. Currently, the researchers in academia as well as in pharmaceutical industries have been developing various methods for the chemical synthesis of indole based compounds via green approaches to overcome the drawbacks of conventional methods. This review reflects the last ten years developments of the various greener methods for the synthesis of indole derivatives by using microwave, ionic liquids, water, ultrasound, nanocatalyst, green catalyst, multicomponent reaction and solvent-free reactions etc. (please see the scheme below). Furthermore, the applications of green chemistry towards developments of indole containing pharmaceuticals and their biological studies have been represented in this review.

Synthesis of 3-(Cyclohexylamino)-2-arylimidazo[1,2-a]pyridine-8- carboxylic Acids Via an Efficient Three-component Condensation Reaction between Cyclohexylisocyanide and 2-Aminopyridine-3-carboxylic Acid in the Presence of Aromatic Aldehyde

2018 ◽  
Vol 21 (4) ◽  
pp. 298-301 ◽  
Author(s):  
Ghasem Marandi
Keyword(s):  
Biological Sciences ◽  
Carboxylic Acid ◽  
Carboxylic Acids ◽  
High Performance ◽  
Condensation Reaction ◽  
Aromatic Aldehydes ◽  
New Materials ◽  
One Pot ◽  
High Yields ◽  
Benzaldehyde Derivatives

Aim and Objective: The reaction of cyclohexylisocyanide and 2-aminopyridine-3- carboxylic acid in the presence of benzaldehyde derivatives in ethanol led to 3-(cyclohexylamino)-2- arylimidazo[1,2-a]pyridine-8-carboxylic acids in high yields. In a three component condensation reaction, isocyanide reacts with 2-aminopyridine-3-carboxylic acid and aromatic aldehydes without any prior activation. Material and Methods: The synthesized products have stable structures which have been characterized by IR, 1H, 13C and Mass spectroscopy as well as CHN-O analysis. Results: In continuation of our attempts to develop simple one-pot routes for the synthesis of 3- (cyclohexylamino)-2-arylimidazo[1,2-a]pyridine-8-carboxylic acids, aromatic aldehydes with divers substituted show a high performance. Conclusion: In conclusion, this study introduces the art of combinatorial chemistry using a simple one-pot procedure for the synthesis of new materials which are interesting compounds in medicinal and biological sciences.

Direct conversion of cellulose to high-yield methyl lactate over Ga-doped Zn/H-nanozeolite Y catalysts in supercritical methanol

2017 ◽  
Vol 19 (8) ◽  
pp. 1969-1982 ◽  
Author(s):  
Deepak Verma ◽  
Rizki Insyani ◽  
Young-Woong Suh ◽  
Seung Min Kim ◽  
Seok Ki Kim ◽  
...  
Keyword(s):  
Lignocellulosic Biomass ◽  
Value Added ◽  
Direct Conversion ◽  
High Yield ◽  
Supercritical Methanol ◽  
Methyl Lactate ◽  
High Yields

For realizing sustainable bio-based refineries, it is crucial to obtain high yields of value-added chemicalsviadirect conversion of cellulose and lignocellulosic biomass.

scholarly journals Physico-Chemical Investigations in the Amide Group

1906 ◽  
Vol 25 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Charles E. Fawsitt
Keyword(s):  
Aqueous Solutions ◽  
Carboxylic Acids ◽  
Amide Group ◽  
Chemical Dynamics ◽  
Physico Chemical ◽  
Other Substances ◽  
The Subject

Some time ago, while studying the chemical dynamics of the changes which occur in solutions of urea or carbamide, I came upon some rather unexpected results which led me to hope that investigations conducted on somewhat the same lines with other substances of the amide group might prove to yield results of some interest. The amides referred to are those derived from carboxylic acids. While proceeding to this investigation I noticed some measurements, obtained in connection with the viscosity of aqueous solutions of carbamide, which appeared of sufficient interest to demand an inquiry into the nature of solutions of this class of substances before proceeding further with the subject of inquiry in the manner at first intended.

scholarly journals Twenty-five tonnes of high quality forages annually in Canterbury

2004 ◽  
pp. 85-91
Author(s):  
T.J. Fraser ◽  
T.L. Knight ◽  
I.M. Knowles ◽  
M.G. Hyslop
Keyword(s):  
Lower Cost ◽  
Forage Yield ◽  
Dairy Calves ◽  
Forage Production ◽  
High Quality ◽  
Cereal Breeding ◽  
Significant Difference ◽  
Recent Developments ◽  
High Yields ◽  
Final Harvest

Recent developments in cereal breeding for forage production have given the potential to greatly increase annual forage dry matter (DM) production. This paper reports on the findings from two cereal forage production trials on irrigated Canterbury land. Trial 1 studied the potential of a range of single and multi-grazed cereal forages over a 9 month period to produce high yields and quality from both grazing and whole-crop silage forage. Trial 2 studied the suitability of different cereal/ legume combinations for green-chop silage grown over a three month summer period. These two cereal forage systems, when combined in a 12 month period, produced in excess of 25 tonnes of high quality forage per hectare, almost double the DM production achieved using current perennial pasture based systems. Trial 1 showed no significant difference in the total DM produced by either single or multi-graze treatments. In Trial 2 pea/cereal combinations produced over 6 t DM/ha. Due to an earlier final harvest the multi-graze system is more easily combined with the summer crop and more likely to produce a lower cost and more sustainable forage system. Animal performance on forage produced in Trial 1 showed that dairy calves can grow well on cereal forages during winter. Keywords: cereal, feed supplements, forage, forage yield, legume, silage

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