Helical Phenanthrenes, Part 5. Synthesis of Pentahelicene-7,8-dione via Intramolecular Benzoin Condensation

2000 ◽  
Vol 65 (4) ◽  
pp. 555-560 ◽  
Author(s):  
Anja Modler-Spreitzer ◽  
Rainer Fritsch ◽  
Albrecht Mannschreck
Keyword(s):  
New Synthesis ◽  
Benzoin Condensation ◽  
Original Preparation

The intramolecular benzoin condensation of [1,1'-binaphthyl]-2,2'-dicarbaldehyde (5), followed by oxidation with air, provides a new synthesis of (MP)-pentahelicene-7,8-dione (1). With reference to the original preparation of this quinone via acyloin condensation, its present yield (73% for the ring-closing step) is considerably increased.

Tandem Carbon-Radical Peroxidation−Addition to Carbonyl Groups Reaction. A New Synthesis of Steroidal β-Peroxy Lactones

1996 ◽  
Vol 61 (26) ◽  
pp. 9635-9635
Author(s):  
Alicia Boto ◽  
Rosendo Hernández ◽  
Ernesto Suárez ◽  
Carmen Betancor ◽  
María S. Rodríguez
Keyword(s):  
Carbonyl Groups ◽  
New Synthesis

1,3-Selenaphospholes: A New Synthesis from 1,2,3-Selenadiazoles and Kinetically Stabilized Phosphaalkynes1

Synlett ◽  
1991 ◽  
Vol 1991 (04) ◽  
pp. 356-358 ◽  
Author(s):  
Bernd Burkhart ◽  
Steffen Krill ◽  
Yoshinori Okano ◽  
Wataru Ando ◽  
Manfred Regitz
Keyword(s):  
New Synthesis

A New Synthesis and Analysis of Silica Nanowire Periodically Wrapped by Nano-spheres

2016 ◽  
Vol 31 (5) ◽  
pp. 523
Author(s):  
MA Hong-Bing ◽  
BAI Hua ◽  
XUE Chen ◽  
TAO Peng-Fei ◽  
XU Qun-Feng ◽  
...  
Keyword(s):  
New Synthesis

New Synthesis of Isoindolo[2,1–b]isoquinolines. Preparation and Aqueous Bioavailability of its Silica Nanoparticles Hybrid System

2015 ◽  
Vol 19 (13) ◽  
pp. 1292-1300 ◽  
Author(s):  
Amelia Diaz ◽  
J. Manuel Lopez–Romero ◽  
Rafael Contreras-Caceres ◽  
Manuel Algarra ◽  
Rodrigo Rico ◽  
...  
Keyword(s):  
Silica Nanoparticles ◽  
Hybrid System ◽  
New Synthesis

A Short Synthesis of the Plant Alkaloid 4-Methyl-2,6-naphthyridine

2019 ◽  
Vol 16 (12) ◽  
pp. 931-934 ◽  
Author(s):  
Alexandra Kamlah ◽  
Franz Bracher
Keyword(s):  
Pyridine Ring ◽  
Cross Coupling ◽  
Antirrhinum Majus ◽  
New Synthesis ◽  
Short Synthesis ◽  
Regioselective Oxidation ◽  
Key Steps

: A new synthesis of the 2,6-naphthyridine alkaloid 4-methyl-2,6-naphthyridine from Antirrhinum majus has been developed. Key steps are a regioselective oxidation of 3-bromo-4,5- dimethylpyridine to the corresponding 4-formyl derivative, and the annulation of the second pyridine ring by Suzuki-Miyaura cross-coupling using (E)-2-ethoxyvinylboronic acid pinacol ester as a masked acetaldehyde equivalent. This protocol gives the alkaloid in four steps starting from commercially available 3,4-dimethylpyridine in 15% overall yield. This annulation protocol should be useful for the synthesis of other condensed pyridines as well.

Synthesis, Analytical Characterization and Spectroscopic Investigation of Chloramphenicol Impurity A for the Quality Control of Chloramphenicol and its Formulation as Per International Compendium

2020 ◽  
Vol 17 (5) ◽  
pp. 382-388
Author(s):  
Aparna Wadhwa ◽  
Faraat Ali ◽  
Sana Parveen ◽  
Robin Kumar ◽  
Gyanendra N. Singh
Keyword(s):  
Quality Control ◽  
Synthesis Method ◽  
Analytical Techniques ◽  
International Markets ◽  
Therapeutic Effects ◽  
Reference Standard ◽  
Working Standard ◽  
Prior Art ◽  
New Synthesis ◽  
Synthetic Procedure

Objective: The main aim of the present work is to synthesize chloramphenicol impurity A (CLRMIMP- A) in the purest form and its subsequent characterization by using a panel of sophisticated analytical techniques (LC-MS, DSC, TGA, NMR, FTIR, HPLC, and CHNS) to provide as a reference standard mentioned in most of the international compendiums, including IP, BP, USP, and EP. The present synthetic procedure has not been disclosed anywhere in the prior art. Methods: A simple, cheaper, and new synthesis method was described for the preparation of CLRM-IMP-A. It was synthesized and characterized by FTIR, DSC, TGA, NMR (1H and 13C), LC-MS, CHNS, and HPLC. Results: CLRM-IMP-A present in drugs and dosage form can alter the therapeutic effects and adverse reaction of a drug considerably, it is mandatory to have a precise method for the estimation of impurities to safeguard the public health. Under these circumstances, the presence of CLRM-IMP-A in chloramphenicol (CLRM) requires strict quality control to satisfy the specified regulatory limit. The synthetic impurity obtained was in the pure form to provide a certified reference standard or working standard to stakeholders with defined potency. Conclusion: The present research describes a novel technique for the synthesis of pharmacopoeial impurity, which can help in checking/controlling the quality of the CLRM in the international markets.

Application of Nitrogen Heterocyclic Carbenes in Organocatalysis

2020 ◽  
Vol 09 ◽  
Author(s):  
Minita Ojha ◽  
R. K. Bansal
Keyword(s):  
Asymmetric Catalysis ◽  
Building Blocks ◽  
Structural Features ◽  
Heterocyclic Carbenes ◽  
Stetter Reaction ◽  
Metal Pollutants ◽  
Synthetic Strategy ◽  
Wide Range ◽  
Benzoin Condensation ◽  
Nitrogen Heterocyclic

Background: During the last two decades, horizon of research in the field of Nitrogen Heterocyclic Carbenes (NHC) has widened remarkably. NHCs have emerged as ubiquitous species having applications in a broad range of fields, including organocatalysis and organometallic chemistry. The NHC-induced non-asymmetric catalysis has turned out to be a really fruitful area of research in recent years. Methods: By manipulating structural features and selecting appropriate substituent groups, it has been possible to control the kinetic and thermodynamic stability of a wide range of NHCs, which can be tolerant to a variety of functional groups and can be used under mild conditions. NHCs are produced by different methods, such as deprotonation of Nalkylhetrocyclic salt, transmetallation, decarboxylation and electrochemical reduction. Results: The NHCs have been used successfully as catalysts for a wide range of reactions making a large number of building blocks and other useful compounds accessible. Some of these reactions are: benzoin condensation, Stetter reaction, Michael reaction, esterification, activation of esters, activation of isocyanides, polymerization, different cycloaddition reactions, isomerization, etc. The present review includes all these examples published during the last 10 years, i.e. from 2010 till date. Conclusion: The NHCs have emerged as versatile and powerful organocatalysts in synthetic organic chemistry. They provide the synthetic strategy which does not burden the environment with metal pollutants and thus fit in the Green Chemistry.

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