The Experts below are selected from a list of 19326 Experts worldwide ranked by ideXlab platform
Ying-feng Han - One of the best experts on this subject based on the ideXlab platform.
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Supramolecular Control of Photocycloadditions in Solution: In Situ Stereoselective Synthesis and Release of Cyclobutanes
Angewandte Chemie (International ed. in English), 2019Co-Authors: Li‐ying Sun, Yao-yu Wang, F. Ekkehardt Hahn, Ying-feng HanAbstract:A new class of supramolecular metallacycles capable of undergoing photochemical reactions and in situ release of Cyclobutanes in solution is described. The molecular metallacycles were generated through coordination-driven self-assembly of dinuclear metal-carbene complexes as organometallic clips with olefin-functionalized bridging ligands. Photolysis of these molecular metallacycles in situ led to structural interconversion and release of the formed Cyclobutane products with quantitative conversion. Further modifications of the obtained Cyclobutanes provided a series of new species containing the Cyclobutane skeleton.
Faiz Ahmed Khan - One of the best experts on this subject based on the ideXlab platform.
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An unusual fragmentation of oxetane-embedded tetracyclic ketal systems.
The Journal of organic chemistry, 2013Co-Authors: G. Hari Mangeswara Rao, Faiz Ahmed KhanAbstract:An unusual route for the synthesis of functionalized Cyclobutane derivatives starting from functionalized norbornane derivatives is reported. Base-induced fragmentation of an oxetanol-type moiety embedded in a tetracyclic norbornyl ketal leads to a Cyclobutane-fused derivative as the major or exclusive product. The fragmentation reaction for bridgehead-bromine-substituted derivatives was much faster than for the corresponding chlorine-substituted substrates. The functionalized Cyclobutane product was formed exclusively in high yield in the former case, while the latter furnished a minor uncyclized side product in varying yields.
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An Unusual Fragmentation of Oxetane-Embedded Tetracyclic Ketal Systems
2013Co-Authors: Hari Mangeswara G. Rao, Faiz Ahmed KhanAbstract:An unusual route for the synthesis of functionalized Cyclobutane derivatives starting from functionalized norbornane derivatives is reported. Base-induced fragmentation of an oxetanol-type moiety embedded in a tetracyclic norbornyl ketal leads to a Cyclobutane-fused derivative as the major or exclusive product. The fragmentation reaction for bridgehead-bromine-substituted derivatives was much faster than for the corresponding chlorine-substituted substrates. The functionalized Cyclobutane product was formed exclusively in high yield in the former case, while the latter furnished a minor uncyclized side product in varying yields
Phil S Baran - One of the best experts on this subject based on the ideXlab platform.
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applications of c h functionalization logic to Cyclobutane synthesis
Journal of Organic Chemistry, 2014Co-Authors: Will R Gutekunst, Phil S BaranAbstract:The application of C–H functionalization logic to target-oriented synthesis provides an exciting new venue for the development of new and useful strategies in organic chemistry. In this article, C–H functionalization reactions are explored as an alternative approach to access pseudodimeric Cyclobutane natural products, such as the dictazole and the piperarborenine families. The use of these strategies in a variety of complex settings highlights the subtle geometric, steric, and electronic effects at play in the auxiliary guided C–H functionalization of Cyclobutanes.
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total synthesis and structural revision of the piperarborenines via sequential Cyclobutane c h arylation
Journal of the American Chemical Society, 2011Co-Authors: Will R Gutekunst, Phil S BaranAbstract:A strategy for the construction of unsymmetrical Cyclobutanes using C–H functionalization logic is demonstrated in the total synthesis of piperarborenine B and piperarborenine D (reported structure). These syntheses feature a new preparation of cis-Cyclobutane dicarboxylates from commercially available coumalate starting materials and a divergent approach to the controlled cis or trans installation of the two distinct aryl rings found in the natural products using the first example of Cyclobutane C–H arylation. The structure of piperarborenine D is reassigned to a head-to-head dimer, which was synthesized using an intramolecular [2+2] photocycloaddition strategy.
Masataka Ihara - One of the best experts on this subject based on the ideXlab platform.
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Cyclobutane ring formation by triflic imide catalyzed 2 2 cycloaddition of allylsilanes
Tetrahedron Letters, 2006Co-Authors: Kiyosei Takasu, Norihiko Hosokawa, Kazato Inanaga, Masataka IharaAbstract:Abstract Cyclobutane forming [2+2]-cycloaddition reactions of allylsilane with electron-deficient olefin is promoted by triflic imide (Tf 2 NH). Triflic imide is converted in situ to silyl triflic imide (R 3 SiNTf 2 ), which serves as the actual catalyst for this process. When these reactions take place at higher than ambient temperatures, thermodynamically more stable anti -Cyclobutanes are generated preferentially by equilibration of the initially formed adducts via retro [2+2]-cycloaddition.
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catalytic 2 2 cycloaddition reactions of silyl enol ethers a convenient and stereoselective method for Cyclobutane ring formation
Journal of Organic Chemistry, 2004Co-Authors: Kiyosei Takasu, Kazato Inanaga, Megumi Ueno, Masataka IharaAbstract:An efficient catalytic (2 + 2)-cycloaddition reaction leading to the formation of Cyclobutane rings has been devised. The process transforms silyl enol ethers and α,β-unsaturated esters into polysubstituted Cyclobutanes with a high degree of trans-stereoselectivity. Both the rate and stereoselectivity of the process can be controlled by the choice of the ester group and silyl substituents. The results of stereochemical studies show that the cycloaddition step in this reaction proceeds in a nonstereospecific manner and, thus, by a pathway involving sequential nucleophilic additions via a short-lived zwitterionic intermediate.
Nadia Chouini-lalanne - One of the best experts on this subject based on the ideXlab platform.
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Formation of Cyclobutane thymine dimers by tiaprofenic acid and its photoproducts: approach to the photosensitizer triplet state energy limit value
RSC Advances, 2015Co-Authors: Sandra Michaud, Guillaume Bordeau, Valérie Sartor, Jose L. Bourdelande, Jordi Hernando, Gonzalo Guirado, Nadia Chouini-lalanneAbstract:Cyclobutane thymine dimers, the major photoproducts produced in UV-irradiated DNA, are the main causative agents for mutagenesis and skin cancer. This lesion can also be initiated under UVA radiation, involving triplet–triplet energy transfer mechanism from a photosensitizer to the thymine nucleobase. According to previous reports, only photosensitizers with a triplet state energy >270 kJ mol−1 should be able to induce Cyclobutane thymine dimers photosensitization. However, tiaprofenic acid, a non-steroidal anti-inflammatory drug widely prescribed in the treatment of inflammation and pain, has shown Cyclobutane thymine dimers photosensitization, although its triplet energy state value and those of its photoproducts are lower than the one previously reported for thymine in DNA. In this context, the in vitro photosensitizing properties of tiaprofenic acid and its photoproducts were studied by agarose gel electrophoresis and phosphorescence experiments and demonstrated clearly the formation of Cyclobutane thymine dimers by tiaprofenic acid and its photoproducts. This study allows us to approach the lower limit threshold of the triplet state energy of a photosensitizer for Cyclobutane thymine dimers formation and thereby to improve the prediction of the photogenotoxic potential of current and future drugs.
