- Transformation of γ-ketoaldehyde acetals into 3-substituted-2-cyclopentenones via cyanophosphates under mild conditions
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The reaction of cyanophosphates, which are readily derived from γ-ketoaldehyde acetals, with TMSN3 (3 eq)/Bu2SnO (0.3 eq) in refluxing toluene directly furnished 3-substituted-2-cyclopentenones in modest to good yield under mild conditions. The present method was further applied toward the synthesis of dechlorotrichodenone C isolated from Trichoderma asperellum.
- Yoneyama, Hiroki,Takatsuji, Kumi,Ito, Aiko,Usami, Yoshihide,Harusawa, Shinya
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- Access to diversely α-substituted cyclopentenones from α-chlorocyclopentenones
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α-Chlorocyclopentenones can readily be transformed into a variety of I?±-substituted cyclopentenones via their dimethyltrimethylene acetals.
- Giannini, Audrey,Coquerel, Yoann,Greene, Andrew E.,Deprés, Jean-Pierre
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p. 6749 - 6751
(2007/10/03)
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- DIRHODIUM TETRAACETATE-CATALYZED DECOMPOSITION OF β,γ-UNSATURATED DIAZO KETONES: A NEW ENTRY TO VINYLOGOUS WOLFF REARRANGEMENT
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Dirhodium tetraacetate-catalyzed decomposition of the β,γ-unsaturated diazo ketones 1 - 4, in the presence of methanol, leads to γ,δ-unsaturated esters 5 - 8 via zwitterionic intermediates (i.e., d).
- Ceccherelli, Paolo,Curini, Massimo,Marcotullio, Maria Carla,Rosati, Ornelio
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p. 177 - 180
(2007/10/02)
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- Catalytic Role of Copper Triflate in Lewis Acid Promoted Reactions of Diazo Compounds
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Copper(II)trifluoromethanesulfonate is often a superior catalyst for transformations of diazo compounds that are normally promoted by boron trifluoride etherate.Formal carbon-oxygen insertion occurs when ortho esters are reacted with diazocarbonyl compounds in the presence of Cu(OTf)2, although the use of BF3*Et2O provides higher yields of insertion products.In contrast, the β,γ-unsaturated diazo ketone 6 undergoes intramolecular cyclization to produce the corresponding cyclopentenone in higher yield with Cu(OTf)2 catalysis than with the use of BF3*Et2O.Intamolecular cyclopropanation of the γ,δ-unsaturated diazo ketone 8 occurs in exceptionally high yield in the presence of Cu(OTf)2, whereas with BF3*Et2O intramolecular cyclization occurs with extensive rearrangement anf fluoride transfer.Copper(II)triflate is unique among transition-metal catalysts that are normally employed for reactions with diazo compounds in its effectiveness for these transformations.
- Doyle, Michael P.,Trudell, Mark L.
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p. 1196 - 1199
(2007/10/02)
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