Radical cyclisation : synthesis of 4H-furo(3,2-c)-1-benzopyrans
TL;DR: In this article, 3,4-dihydro-3-bromo-4-(prop-2-ynyloxy)-2H-1-benzopyrans (3) undergo radical cyclisation when treated with nBu 3 SnH and AIBN.
About: This article is published in Tetrahedron Letters.The article was published on 1988-01-01. It has received 8 citations till now. The article focuses on the topics: Benzopyrans & Yield (chemistry).
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TL;DR: Cyclisations cationiques, radicalaires and anioniques as discussed by the authors are catalysees par des metaux, and they can be classified into three classes: cationique, radicalaine and radicalaine.
73 citations
TL;DR: Radical cyclization reactions are among the most powerful and versatile methods for the construction of mono-and polycyclic systems as discussed by the authors, which offer high functional group tolerance and mild reaction conditions combined with high levels of regio- and stereochemistry.
Abstract: Radical cyclization reactions are among the most powerful and versatile methods for the construction of mono- and polycyclic systems. The advantages these reactions offer to the synthetic organic chemist include high functional group tolerance and mild reaction conditions combined with high levels of regio- and stereochemistry. Furthermore, the recent progress in radical chemistry has led to the development of a broad range of very useful practical methods to conduct radical cyclization reactions. In general, radical cyclization reactions comprise three basic steps: selective radical generation, radical cyclization, and conversion of the cyclized radical to the product.
For the generation of the initial radical a broad variety of suitable precursors can be employed, such as halides, thio- and selenoethers, alcohols, aldehydes and hydrocarbons. The cyclization step usually involves the intramolecular addition of a radical to a multiple bond. Most often carbon–carbon multiple bonds are employed; however, there are also examples known for the addition to carbon–oxygen and carbon–nitrogen bonds. Depending on the method employed, the cyclized radical is converted to the desired product by trapping with a radical scavenger, by a fragmentation reaction, or by an electron transfer reaction.
The section Mechanism, Regio- and Stereochemistry provides an introduction to the key features of radical cyclization with a special emphasis on the factors controlling the regio- and stereochemistry. The section Scope and Limitations covers the different methods used to conduct radical cyclization. The basic principles of radical chemistry and general practical considerations when conducting radical cyclizations are not discussed in detail. Several excellent review articles and books dealing with these topics are available.
Keywords:
radical cyclization reactions;
mechanism;
regiochemistry;
steroechemistry;
small rings;
scope;
limitations;
medium-sized rings;
formation;
monocycles;
macrocyclizations;
bi-cycles;
polycycles;
metal hydride;
tin hydride;
mercury hydride;
fragmentation methods;
thiohydroxamine;
methods;
Barton method;
atom transfer;
hydrogen atom transfer;
halogen atom transfer;
radical/radical coupling;
redox methods;
sequential reactions;
experimental conditions;
experimental procedures;
comparison of methods;
tabular survey
58 citations
TL;DR: The first total synthesis of (+)-lophirone H (1) and its pentamethyl ether 29, featuring an oxonium-Prins cyclization/benzylic cation trapping reaction, is described.
26 citations
TL;DR: The phytochemistry of Anthocephalus cadamba is reviewed and its application in the treatment of various ailments like diabetes mellitus, diarrhoea, fever, inflammation, haemoptysis, cough, vomiting, wounds, ulcers, debility and antimicrobial activity is reviewed.
24 citations
TL;DR: Both lipid lowering and antioxidant activities in root extract of A. indicus are demonstrated, which could help prevention of hyperlipidemia and related diseases.
Abstract: The lipid lowering activity of Anthocephalus indicus (family Rubiaceae; Hindi name Kadamba) root extract has been studied in triton WR-1339 induced hyperlipidemia in rats. In this model, feeding with root extract (500 mg kg−1 b.w.) lowered plasma lipids and reactivated post-heparin lipolytic activity in hyperlipidemic rats. Furthermore, the root extract (50–500 μM) inhibited the generation of superoxide anions and hydroxyl radicals, in both enzymic and non-enzymic systems, in vitro. The results of the present study demonstrated both lipid lowering and antioxidant activities in root extract of A. indicus, which could help prevention of hyperlipidemia and related diseases.
23 citations
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592 citations
446 citations
TL;DR: Apres avoir forme les enamines de plusieurs cetones: cyclopentanone, cyclohexanone and nonanone-5 etc as discussed by the authors.
Abstract: Apres avoir forme les enamines de plusieurs cetones: la cyclopentanone, la cyclohexanone, la nonanone-5 etc… on leur additionne selon Michael C=C(SePh)CN ou C=C(SePh)SO 2 Ph puis R-C≡Cli (ou R=CH 3 ou EtO). On obtient respectivement un hydroxy-1 bicyclo [3.3.0] octanecarbonitrile-3, un hydroxy-1 bicyclo [4.3.0] nonanecarbonitrile-3, un hydroxy-3 cyclopentanecarbonitrile
39 citations
TL;DR: The Claisen rearrangement of aryl propargyl ethers in poly(ethylene glycol) -200 at 200°C affords products in good yields.
38 citations
TL;DR: The furobenzopyran derivatives (1a, b) and (1b) have been prepared by a simple route from m-methoxy-phenol as discussed by the authors.
Abstract: The furobenzopyran derivatives (1a) and (1b) have been prepared by a simple route from m-methoxy-phenol.
14 citations