Rules for ring closure
01 Jan 1976-Journal of The Chemical Society, Chemical Communications (The Royal Society of Chemistry)-Iss: 18, pp 734-736
TL;DR: The endocyclic closure of nucleophilic centres to polarized double bonds to give five-membered rings is impeded by restrictions of geometry; these restrictions can be overcome in acid through the generation of oxonium or protonated forms.
Abstract: Three rules which have been found useful, on an empirical basis, to predict the relative facility of ring forming reactions are presented; the physical bases of such rules are described.
Citations
More filters
TL;DR: The spiro[pyrrolidine-3,3′-oxindole] ring system is found at the core of a number of alkaloids, which possess significant biological activity and are interesting, challenging targets for chemical synthesis as discussed by the authors.
1,267 citations
TL;DR: Organic fluorine compounds have received a great deal of interest and attention from the scientists involved in diverse fields of science and technology and not only C-F bond formation but also selective C-f bond activation have become current subjects of active investigation from the viewpoint of effective synthesis of fluoroorganic compounds.
Abstract: Fluorine has received great attention in all fields of science. “Small atom with a big ego” was the title of the Symposium at the ACS meeting in San Francisco in 2000, where a number of the current scientific and industrial aspects of fluorine chemistry made possible by the small size and high electronegativity of the atom were discussed. This small atom has provided mankind with significant benefits in special products such as poly(tetrafluroethylene) (PTFE), freon, fluoro-liquid crystals, optical fiber, pharmaceutical and agrochemical compounds, and so on, all of which have their own unique properties that are otherwise difficult to obtain.1 For instance, at present, up to 30% of agrochemicals and 10% of pharmaceuticals currently used contain fluorine atoms. Therefore, organic fluorine compounds have received a great deal of interest and attention from the scientists involved in diverse fields of science and technology. Now, not only C-F bond formation but also selective C-F bond activation have become current subjects of active investigation from the viewpoint of effective synthesis of fluoroorganic compounds. The former is highlighted by designing a sophisticated fluorinating reagent for regioand stereocontrolled fluorination and developing versatile multifunctional and easily prepared building blocks. C-F bond formation has been treated extensively in several reviews2 and books.3 The latter is a subject that has been less explored but would be promising for selective defluorination of aliphatic fluorides, cross-coupling with aryl fluorides, and * To whom correspondence should be addressed. Phone: 81-78-803-5799. Fax: 81-78-803-5799. E-mail: amii@kobe-u.ac.jp and uneyamak@cc.okayamau.ac.jp. † Kobe University. ‡ Okayama University. Chem. Rev. 2009, 109, 2119–2183 2119
1,132 citations
TL;DR: A comparison study of the effects of gem-Dialkyl Substitution in Drug Design on the Formation and Stability of Inorganic and Organometallic Complexes and their implications for synthetic chemistry and drug design.
Abstract: 3. Synthetic Applications 1746 3.1. Pericyclic Reactions 1747 3.1.1. Diels−Alder Cycloadditions 1747 3.1.2. Dipolar Cycloadditions 1749 3.1.3. Ene Reactions 1750 3.1.4. Claisen Rearrangements 1750 3.2. Radical Cyclizations 1750 3.3. Transition-Metal-Catalyzed Cyclizations 1753 3.4. Ring-Closing Metathesis 1754 3.5. Electrophilic Cyclizations 1755 3.6. Other Cyclizations 1756 4. Biochemical and Pharmaceutical Implications 1757 4.1. “Trimethyl Lock Effect” 1757 4.2. gem-Dialkyl Substitution in Drug Design 1759 5. Miscellaneous 1762 5.1. gem-Disubstituent Effect on the Formation and Stability of Inorganic and Organometallic Complexes 1762
702 citations
TL;DR: In this article, a theoretical study of the relative rates and the regio-and stereo-chemistry of ring closure of a variety of alkenyl radicals was performed using MM2 force-field calculations.
621 citations
580 citations
References
More filters
7,789 citations
TL;DR: A number of polyfunctional molecules have been examined as substrates for the 5-Endo-Trigonal ring-forming reaction, and it has been found that for first-row elements this is a disfavoured process, alternative reactions of type 5-Exo-trig generally taking precedence.
Abstract: A number of polyfunctional molecules have been examined as substrates for the 5-Endo-Trigonal ring-forming reaction, and it has been found that for first-row elements this is a disfavoured process, alternative reactions of type 5-Exo-Trig generally taking precedence; one case of a 5-Endo-Trig closure for a second-row element, sulphur, has been found.
324 citations
210 citations
TL;DR: In this paper, a vector analysis method based on classical Lewis resonance structures is used to approximate preferred nucleophilic approach geometries to unsaturated functions, and the application of this approach vector analysis to the stereochemistry of enone reductions is explained.
Abstract: A method of approximating preferred nucleophilic approach geometries to unsaturated functions, based on classical Lewis resonance structures, is described; the application of this approach vector analysis method to the stereochemistry of enone reductions is explained.
125 citations
115 citations