Imidates: an emerging synthon for N-heterocycles

2019 ◽  
Vol 17 (46) ◽  
pp. 9829-9843 ◽  
Author(s):  
Rima Thakur ◽  
Yogesh Jaiswal ◽  
Amit Kumar
Keyword(s):  
Base Metal ◽  
Building Blocks ◽  
Recent Application ◽  
Acid Base ◽  
Reaction Conditions ◽  
Metal Catalyzed

This review highlights the recent application of imidates as building blocks for the synthesis of saturated and un-saturated N-heterocycles via C–N annulation reactions under acid/base/metal-catalyzed/radical-mediated reaction conditions.

scholarly journals Base Metal Catalysts for Deoxygenative Reduction of Amides to Amines

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 490 ◽  
Author(s):  
Andrey Khalimon ◽  
Kristina Gudun ◽  
Davit Hayrapetyan
Keyword(s):  
Base Metal ◽  
Precious Metals ◽  
Building Blocks ◽  
Metal Catalysts ◽  
Environmentally Benign ◽  
Attractive Alternative ◽  
Catalytic Systems ◽  
Amide Carbonyl ◽  
Amide Carbonyl Group ◽  
Metal Catalyzed

The development of efficient methodologies for production of amines attracts significant attention from synthetic chemists, because amines serve as essential building blocks in the synthesis of many pharmaceuticals, natural products, and agrochemicals. In this regard, deoxygenative reduction of amides to amines by means of transition-metal-catalyzed hydrogenation, hydrosilylation, and hydroboration reactions represents an attractive alternative to conventional wasteful techniques based on stoichiometric reductions of the corresponding amides and imines, and reductive amination of aldehydes with metal hydride reagents. The relatively low electrophilicity of the amide carbonyl group makes this transformation more challenging compared to reduction of other carbonyl compounds, and the majority of the reported catalytic systems employ precious metals such as platinum, rhodium, iridium, and ruthenium. Despite the application of more abundant and environmentally benign base metal (Mn, Fe, Co, and Ni) complexes for deoxygenative reduction of amides have been developed to a lesser extent, such catalytic systems are of great importance. This review is focused on the current achievements in the base-metal-catalyzed deoxygenative hydrogenation, hydrosilylation, and hydroboration of amides to amines. Special attention is paid to the design of base metal catalysts and the mechanisms of such catalytic transformations.

scholarly journals A Sustainable Improvement of ω-Bromoalkylphosphonates Synthesis to Access Novel KuQuinones

Organics ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 107-117
Author(s):  
Mattia Forchetta ◽  
Valeria Conte ◽  
Giulia Fiorani ◽  
Pierluca Galloni ◽  
Federica Sabuzi
Keyword(s):  
Metal Oxides ◽  
Phosphonic Acid ◽  
Organic Molecules ◽  
Building Blocks ◽  
Reaction Conditions ◽  
Phosphonic Acids ◽  
Sustainable Improvement ◽  
Phosphonate Esters ◽  
First Time ◽  
Complex Organic

Owing to the attractiveness of organic phosphonic acids and esters in the pharmacological field and in the functionalization of conductive metal-oxides, the research of effective synthetic protocols is pivotal. Among the others, ω-bromoalkylphosphonates are gaining particular attention because they are useful building blocks for the tailored functionalization of complex organic molecules. Hence, in this work, the optimization of Michaelis–Arbuzov reaction conditions for ω-bromoalkylphosphonates has been performed, to improve process sustainability while maintaining good yields. Synthesized ω-bromoalkylphosphonates have been successfully adopted for the synthesis of new KuQuinone phosphonate esters and, by hydrolysis, phosphonic acid KuQuinone derivatives have been obtained for the first time. Considering the high affinity with metal-oxides, KuQuinones bearing phosphonic acid terminal groups are promising candidates for biomedical and photo(electro)chemical applications.

Pyrido[1,2-a]pyrazine - Startprodukte für regioselektive Ringtransformationen und supramolekulare Architekturen / Pyrido[1,2-a]pyrazines - Starting Materials for Regioselective Ringtransformation Reactions and Supramolecular Architectures

2002 ◽  
Vol 57 (4) ◽  
pp. 471-478 ◽  
Author(s):  
D. Müller ◽  
B. Frank ◽  
R. Beckert ◽  
H. Görls
Keyword(s):  
Cycloaddition Reaction ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Building Blocks ◽  
Ring Transformation ◽  
Supramolecular Architectures ◽  
Cross Coupling Reaction ◽  
Metal Catalyzed

The easily available pyrido[1,2-a]pyrazines of type 1 are versatile building blocks for ring transformation reactions.W ith heterocyclic quinones such as quinoline-2,5,8-triones 4a-c, a highly regioselective [4+2]-cycloaddition reaction takes place in the first step, followed by a ring transformation cascade.T he 1,6-diazaanthracene-2,9,10-triones 5a-e, which possess an additional bipyridine substructure, could be isolated as main products.In order to modify the starting products of type 1, a metal-catalyzed cross-coupling reaction with acetylenic benzoic esters 9a,b has been performed.T he modified pyridopyrazines 10a,b which were obtained in good yields could be transformed by analogy to 1a,b into ring-fused heterocyclic quinones 12a,b.

scholarly journals Synthesis of new Cα-tetrasubstituted α-amino acids

2009 ◽  
Vol 5 ◽  
Author(s):  
Andreas A Grauer ◽  
Burkhard König
Keyword(s):  
Amino Acids ◽  
Secondary Structure ◽  
Aromatic Aldehydes ◽  
Building Blocks ◽  
Reaction Conditions ◽  
Peptide Backbone ◽  
Aliphatic Aldehydes ◽  
New Class ◽  
Cyclic Amino Acids

Cα-Tetrasubstituted α-amino acids are important building blocks for the synthesis of peptidemimetics with stabilized secondary structure, because of their ability to rigidify the peptide backbone. Recently our group reported a new class of cyclic Cα-tetrasubstituted tetrahydrofuran α-amino acids prepared from methionine and aromatic aldehydes. We now report the extension of this methodology to aliphatic aldehydes. Although such aldehydes are prone to give aldol products under the reaction conditions used, we were able to obtain the target cyclic amino acids in low to moderate yields and in some cases with good diastereoselectivity.

scholarly journals Synthesis and Antitumor Activity of a Series of Novel 1-Oxa-4-azaspiro[4,5]deca-6,9-diene-3,8-dione Derivatives

Molecules ◽  
2019 ◽  
Vol 24 (5) ◽  
pp. 936
Author(s):  
Ze Yang ◽  
Qiu Zhong ◽  
Shilong Zheng ◽  
Guangdi Wang ◽  
Ling He
Keyword(s):  
Cell Line ◽  
Cell Lines ◽  
Cancer Cell ◽  
Cancer Cell Lines ◽  
Oxidative Cyclization ◽  
Human Lung Cancer ◽  
Reaction Conditions ◽  
Promising Candidate ◽  
Metal Catalyzed ◽  
Further Development

A series of novel 1-oxa-4-azaspiro[4.5]deca-6,9-diene-3,8-diones were designed and synthesized by using 4-aminophenol and α-glycolic acid or lactic acid as starting materials in three or four steps. The key step is the metal-catalyzed oxidative cyclization of the amide to 1-oxa-4-azaspiro[4.5]deca-6,9-diene-3,8-diones (10a and 10b), the reaction conditions of which are investigated and optimized. The anticancer activity of 17 1-oxa-4-azaspiro[4.5]deca-6,9-diene-3,8-dione derivatives was evaluated. Preliminary results showed that 15 compounds have moderate to potent activity against human lung cancer A549, human breast cancer MDA-MB-231, and human cervical cancer HeLa cancer cell lines. Among them, compounds 11b and 11h were the most potent against A549 cell line with 0.18 and 0.19 µM of IC50, respectively; compounds 11d, 11h, and 11k showed the most potent cytotoxicity against MDA-MB-231 cell line with 0.08, 0.08, and 0.09 µM of IC50, respectively, while the activities of 11h, 11k, and 12c against HeLa cell line were the most potent with 0.15, 0.14, and 0.14 µM of IC50, respectively. Compound 11h is a promising candidate for further development, which emerged as the most effective compound overall against the three tested cancer cell lines.

scholarly journals NaIO4/Br- as a mild system for the oxidation of 1-methyl-anthra-9,10-quinones

2015 ◽  
Author(s):  
Marcin Cybulski ◽  
Adam Formela ◽  
Katarzyna Sidoryk ◽  
Olga Michalak ◽  
Anna Rosa ◽  
...  
Keyword(s):  
High Pressure ◽  
Carboxylic Acids ◽  
Scale Up ◽  
Lithium Bromide ◽  
Cost Effective ◽  
Building Blocks ◽  
Multidrug Resistant ◽  
Resistant Cell ◽  
Direct Oxidation ◽  
Reaction Conditions

One of the anthraquinone classes comprises compounds with a carbonyl group. These natural or synthetic anthraquinones find their application as building blocks in the synthesis of the compounds with a biological activity. Recently, 4-substituted anthra-9,10-quinone-1-carboxylic acids (2) have been used as key intermediates in the synthesis of patented compounds (3) with anticancer activity against multidrug resistant cell lines. Although 2,7-dihydro-3H-dibenz[de,h]cinnolin-3,7-diones (3) were successfully synthetized in a small laboratory scale, several problems were observed during the preparation of their acid intermediates (2) in a multi-gram scale. The known methods for the preparation of 2 are based on the oxidation of the methyl group in anthra-9,10-quinones (1). The most common are: the oxidation with the diluted nitric acid under high pressure in a sealed tube at the temperature of 195-220 oC, the oxidation in nitrobenzene by passing chlorine gas through the reaction mixture at the temperature of 160-170 oC or in a presence of the fuming sulphuric acid. The mentioned methods require aggressive reagents and specific reaction conditions including high pressure and temperature. Thus, there was a need to find a new efficient, cost-effective and reproducible synthetic method of preparation of 2. While searching literature it was found that the direct oxidation of alkylarenes mediated by the sodium periodate/lithium bromide combination produces benzyl acetates throughout benzyl bromides in the acetic acid, or benzylic acids in the diluted inorganic acid. Based on these results we examined a variety of reaction conditions with or without the bromine source and the oxidizing anion. As a result, a novel procedure for the preparation of highly pure 4-substituted anthra-9,10-quinone-1-carboxylic acids (HPLC > 99.5%) using oxidizing anion/ brominating reagent system was developed. It enabled 2 isolation by the simple filtration of the reaction mixture and was applied in the scale-up of 2,7-dihydro-3H-dibenz[de,h]cinnolin-3,7-dione derivatives.

MODIFICATION OF POLYBUTADIENE RUBBER: A REVIEW

2021 ◽  
Author(s):  
Parashiva Prabhu C. ◽  
Subhra Mohanty ◽  
Virendra Kumar Gupta
Keyword(s):  
Chain Length ◽  
Industrial Applications ◽  
Global Market ◽  
Specific Method ◽  
Reactivity Ratios ◽  
Reaction Conditions ◽  
Commercial Products ◽  
Polybutadiene Rubber ◽  
Metal Catalyzed

ABSTRACT Developments in modification of polybutadiene rubber (PBR) using various reagents and catalysts have been reviewed. Hydrogenation and functionalization occurring at the site of unsaturation along chain length are discussed. Hydrogenation involving various metal catalyzed processes is discussed. Suitable conditions that are effective during hydrogenation and functionalization are mentioned in this article. Reactivity ratios associated with microstructures of polybutadiene rubber and possible mechanisms involved are described in the review. The importance of reaction conditions during reactivity and their impact on product properties are highlighted. A specific method that needs to be adopted in order to achieve expected product properties is discussed. Various industrial applications of modified PBR and their commercial products in the global market are discussed.

scholarly journals Recent Advances in Homogeneous Metal-Catalyzed Aerobic C–H Oxidation of Benzylic Compounds

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 640 ◽  
Author(s):  
Garazi Urgoitia ◽  
Raul SanMartin ◽  
María Herrero ◽  
Esther Domínguez
Keyword(s):  
Molecular Oxygen ◽  
Aerobic Oxidation ◽  
Key Factors ◽  
Reaction Conditions ◽  
Aromatic Ketones ◽  
Recent Advances ◽  
Metal Catalyzed

Csp3–H oxidation of benzylic methylene compounds is an established strategy for the synthesis of aromatic ketones, esters, and amides. The need for more sustainable oxidizers has encouraged researchers to explore the use of molecular oxygen. In particular, homogeneous metal-catalyzed aerobic oxidation of benzylic methylenes has attracted much attention. This account summarizes the development of this oxidative strategy in the last two decades, examining key factors such as reaction yields, substrate:catalyst ratio, substrate scope, selectivity over other oxidation byproducts, and reaction conditions including solvents and temperature. Finally, several mechanistic proposals to explain the observed results will be discussed.

scholarly journals A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

2019 ◽  
Vol 15 ◽  
pp. 1523-1533 ◽  
Author(s):  
András György Németh ◽  
György Miklós Keserű ◽  
Péter Ábrányi-Balogh
Keyword(s):  
Elemental Sulfur ◽  
Building Blocks ◽  
Reaction Conditions ◽  
One Pot ◽  
Catalyst Free ◽  
Synthetic Procedure ◽  
Three Component Reaction ◽  
Wide Range ◽  
Organic Chemist ◽  
The One

A new multicomponent reaction has been developed between isocyanides, sulfur and alcohols or thiols under mild reaction conditions to afford O-thiocarbamates and dithiocarbamates in moderate to good yields. The one-pot reaction cascade involves the formation of an isothiocyanate intermediate, thus a catalyst-free synthesis of isothiocyanates, as valuable building blocks from isocyanides and sulfur is proposed, as well. The synthetic procedure suits the demand of a modern organic chemist, as it tolerates a wide range of functional groups, it is atom economic and easily scalable.

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