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Ring Expansion (ring + expansion)
Terms modified by Ring Expansion Selected AbstractsGold- and Silver-Catalyzed Tandem Amination/Ring Expansion of Cyclopropyl Methanols with Sulfonamides as an Expedient Route to PyrrolidinesCHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2008Weidong Rao Abstract An efficient synthetic route to pyrrolidines that relies on AuCl/AgOTf-catalyzed tandem amination/ring expansion of substituted cyclopropyl methanols with sulfonamides is reported herein. The reactions proceed rapidly at 100,°C with catalyst loadings as low as 2,mol,% and produce the pyrrolidine products in yields of 30,95,%. The method was shown to be applicable to a broad range of cyclopropyl methanols, including unactivated ones, and sulfonamide substrates containing electron-withdrawing, electron-donating, and sterically-demanding substituents. The mechanism is suggested to involve activation of the alcohol substrate by the AuCl/AgOTf catalyst, followed by ionization of the starting material, which causes ring opening of the cyclopropane moiety and trapping by the sulfonamide nucleophile. The resultant aminated acyclic intermediate undergoes subsequent intramolecular hydroamination to give the pyrrolidine. [source] Selectivity Control in Lewis Acid Catalyzed Regiodivergent Tandem Cationic Cyclization/Ring Expansion Terminated by Pinacol Rearrangement,ANGEWANDTE CHEMIE, Issue 33 2009Lu Liu Auf den Katalysator kommt es an: Die Titelreaktionssequenz überführte 1 in 2, wenn AgSbF6 in DCE verwendet wurde, oder in 3, wenn In(OTf)3 mit MeOH zum Einsatz kam. Die Hauptprodukte wurden jeweils in Verhältnissen bis >20:1 erhalten (siehe Schema; DCE=1,2-Dichlorethan, Tf=Trifluormethansulfonyl). [source] Ring Expansion of 2-(,-Hydroxyalkyl)azetidines: A Synthetic Route to Functionalized PyrrolidinesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2008François Durrat Abstract A series of 2-(,-hydroxyalkyl)azetidines synthesized from enantiomerically pure ,-amino alcohols and presenting various patterns both on the four-membered ring and on the adjacent hydroxy group were treated with either thionyl chloride or methanesulfonyl chloride in the presence of triethylamine. The thus-prepared 2-(,-chloro- or ,-methanesulfonyloxyalkyl)azetidines were shown to rearrange stereospecifically into 3-(chloro- or methanesulfonyloxy)pyrrolidines. When this rearrangement is conducted in the presence of an added nucleophile (NaN3, KCN, KOH, or NaOAc), the produced pyrrolidine incorporates the added nucleophile at C-3 stereospecifically. The relative configuration of the substituents in the formed pyrrolidines is consistent with a mechanism involving the formation of an intermediate bicyclic aziridinium ion, which is opened regioselectively at the bridgehead carbon atom. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Ring Expansion versus Cyclization in 4-Oxoazetidine-2- carbaldehydes Catalyzed by Molecular Iodine: Experimental and Theoretical Study in ConcertADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Benito Alcaide Abstract Molecular iodine (10,mol%) efficiently catalyzes the ring expansion of 4-oxoazetidine-2-carbaldehydes in the presence of tert -butyldimethylsilyl cyanide, or allylic and propargylic trimethylsilanes to afford protected 5-functionalized-3,4-dihydroxypyrrolidin-2-ones with good yield and high diastereoselectivity, through a C3C4 bond cleavage of the ,-lactam nucleus. Interestingly, in contrast to the iodine-catalyzed reactions of 3-alkoxy-,-lactam aldehydes which lead to the corresponding ,-lactam derivatives (rearrangement adducts), the reactions of 3-aryloxy-,-lactam aldehydes under similar conditions gave ,-lactam-fused chromanes (cyclization adducts) as the sole products, through exclusive electrophilic aromatic substitution involving the C3 aromatic ring and the carbaldehyde. In order to support the mechanistic proposals, theoretical studies have been performed. [source] Divergent Reactivity of 2-Azetidinone-Tethered Allenols with Electrophilic Reagents: Controlled Ring Expansion versus SpirocyclizationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2010Benito Alcaide Abstract A dual reactivity of 2-azetidinone-tethered allenols may occur by judicious choice of the electrophilic reagents, namely halogenating versus selenating reagents. Using common substrates, structurally different compounds, namely tetramic acids (from N -bromosuccinimide) or spirocyclic seleno-,-lactams (from N -phenylselenophthalimide), can be readily synthesized by these divergent protocols. [source] Stereoselective Ring Expansion of Vinyl Oxiranes: Mechanistic Insights and Natural Product Total Synthesis,ANGEWANDTE CHEMIE, Issue 9 2010Matthew Brichacek Spannungsabbau: Die erste breit anwendbare, katalytische und stereoselektive Vinyloxiran-Ringerweiterung wird beschrieben (siehe Schema; hfacac=Hexafluoracetylacetonat). Die Stereoselektivität wird durch etliche Reaktionsparameter beeinflusst, und kinetische Studien sprechen für die In-situ-Bildung einer katalytisch aktiven Spezies. Die Reaktion wurde in der asymmetrischen Totalsynthese von (+)-Goniothalesdiol eingesetzt. [source] ChemInform Abstract: Construction of Linked Nitrogen Heterocycles by Palladium(0)-Catalyzed Intramolecular Domino Cyclization of 2-Alkynylaziridines Bearing a 2-Aminoethyl Group via Ring Expansion with Isocyanate.CHEMINFORM, Issue 40 2010Akinori Okano Abstract The Pd-catalyzed reaction of alkynylaziridines of type (I) and (V) with isocyanates provides a new approach to pyrrolinylimidazolidinones and/or imidazolidinyldiazepinones depending on the nature of substituents and conditions used. [source] ChemInform Abstract: Diastereoselective Synthesis of Bicyclic ,-Lactams via Ring Expansion of Monocyclic ,-Lactams.CHEMINFORM, Issue 27 2009Stijn Dekeukeleire Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Stereoselective, Dual-Mode Ruthenium-Catalyzed Ring Expansion of Alkynylcyclopropanols.CHEMINFORM, Issue 19 2009Barry M. Trost Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthesis of Cyclobutenes by Highly Selective Transition-Metal-Catalyzed Ring Expansion of Cyclopropanes.CHEMINFORM, Issue 8 2009Huadong Xu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Efficient Route to 2H-1,3-Oxazines Through Ring Expansion of Isoxazoles by Rhodium Carbenoids.CHEMINFORM, Issue 7 2009James R. Manning Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A Novel NaI-Promoted Ring Expansion of Cyclopropylidene Alcohols to Dihydropyrans.CHEMINFORM, Issue 25 2007Weijun Fu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Synthesis of ,,,-Unsaturated Lactams via a Magnesium Iodide Promoted Ring Expansion of Secondary Methylenecyclopropyl Amides.CHEMINFORM, Issue 14 2007Mark E. Scott Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Ring Expansion of Isopropenyldihydrofuran Derivatives.CHEMINFORM, Issue 41 2006Seiji Yamaguchi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Palladium-Catalyzed Asymmetric Ring Expansion of Allenylcyclobutanols: An Asymmetric Wagner,Meerwein Shift.CHEMINFORM, Issue 39 2006Barry M. Trost Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Tetrahydropyridine (THP) Ring Expansion under the Action of Activated Terminal Alkynes.CHEMINFORM, Issue 20 20065-d]azocines., The First Synthesis, X-Ray Crystal Structure of Tetrahydropyrimido[ Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Rapid Method for the Ring Expansion of 1,3-Dithiolanes and 1,3-Dithianes with tert-Butyl Hypochlorite.CHEMINFORM, Issue 15 2006Nitin D. Arote Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Organocatalytic Ring Expansion of ,-Lactams to ,-Lactams Through a Novel N1,C4 Bond Cleavage.CHEMINFORM, Issue 1 2006Direct Synthesis of Enantiopure Succinimide Derivatives. No abstract is available for this article. [source] Lewis Acid-Catalyzed Stereospecific Ring Expansion of Aziridine-2-carboxylates to Imidazolidin-2-ones.CHEMINFORM, Issue 43 2005Min Sung Kim Abstract For Abstract see ChemInform Abstract in Full Text. [source] A First Example Using o-Iodoxybenzoic Acid (IBX) in Combination with Tetraethylammonium Bromide (TEAB) for Ring Expansion of 1,3-Dithiolanes and 1,3-Dithianes.CHEMINFORM, Issue 41 2005Vidyanand G. Shukla Abstract For Abstract see ChemInform Abstract in Full Text. [source] Diastereoselective Ring Expansion of ,-Lactams Toward ,-Lactams via N-Acyliminium Intermediates.CHEMINFORM, Issue 38 2005Willem Van Brabandt No abstract is available for this article. [source] Aza-Prins-pinacol Approach to 7-Azabicyclo[2.2.1]heptanes and Ring Expansion to [3.2.1]Tropanes.CHEMINFORM, Issue 33 2005Alan Armstrong Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Stereoselective Ring Expansion via Bicyclooxonium Ion.CHEMINFORM, Issue 34 2002A Novel Approach to Oxocanes. Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Ring Expansion: Formal Total Synthesis of (-)-Paroxetine.CHEMINFORM, Issue 5 2002Janine Cossy Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Ring Expansion/Homologation,Aldehyde Condensation Cascade Using tert-Trihalomethylcarbinols.CHEMINFORM, Issue 2 2007J. R. Falck Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Ring Expansions of Tetrahydroprotoberberines and Related Dibenzo[c,g]azecines Modulate the Dopamine Receptor Subtype Affinity and SelectivityARCHIV DER PHARMAZIE, Issue 4 2010Maria Schulze Abstract The affinities of tetrahydroprotoberberines for dopamine receptors dramatically decrease after cleaving the central C-N bond to the analogous ten-membered dibenzo[c,g]azecines [1]. In the present work, we also synthesized eleven-membered homologues of these heterocycles and measured the affinities of the resulting dibenzazaundecenes and their underlying homoberberines for human dopamine receptors as well as the cytotoxic effects of all target compounds on human glia cells. The tetracyclic iso-C-homoberberine-derivatives revealed to be D4 -selective antagonists, while all other active compounds showed a significant D1/D5 selectivity. Distances in energy-minimized conformations were measured in order to explain our findings. [source] Ring Expansions of 2-Alkenylazetidinium Salts , A New Route to Pyrrolidines and Azepanes.CHEMINFORM, Issue 52 2006Francois Couty Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] MgI2 -Mediated Ring Expansions of Secondary Methylenecyclopropyl Amides.CHEMINFORM, Issue 31 2003Mark Lautens Abstract For Abstract see ChemInform Abstract in Full Text. [source] Gold- and Silver-Catalyzed Tandem Amination/Ring Expansion of Cyclopropyl Methanols with Sulfonamides as an Expedient Route to PyrrolidinesCHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2008Weidong Rao Abstract An efficient synthetic route to pyrrolidines that relies on AuCl/AgOTf-catalyzed tandem amination/ring expansion of substituted cyclopropyl methanols with sulfonamides is reported herein. The reactions proceed rapidly at 100,°C with catalyst loadings as low as 2,mol,% and produce the pyrrolidine products in yields of 30,95,%. The method was shown to be applicable to a broad range of cyclopropyl methanols, including unactivated ones, and sulfonamide substrates containing electron-withdrawing, electron-donating, and sterically-demanding substituents. The mechanism is suggested to involve activation of the alcohol substrate by the AuCl/AgOTf catalyst, followed by ionization of the starting material, which causes ring opening of the cyclopropane moiety and trapping by the sulfonamide nucleophile. The resultant aminated acyclic intermediate undergoes subsequent intramolecular hydroamination to give the pyrrolidine. [source] A Nearly Planar Stannene with a Reactive Tin,Carbon Double BondEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008Abdoul Fatah Abstract Bis(2,4,6-triisopropylphenyl)-2,7-di- tert -butylfluorenylidenestannane, Tip2Sn=CR2, an isolable stannene that displays a deep-purple colour, was synthesized by dehydrofluorination of the corresponding fluorostannane by tert -butyllithium. It exhibits the shortest Sn=C distance [2.003(5) Å] and the slightest twisting around this unsaturation (10°) among the known stannenes. Its reaction with benzaldehyde according to a [2+2] cycloaddition and that with ,-ethylenic aldehydes and ketones such as crotonaldehyde and methyl vinyl ketone by a [2+4] cycloaddition proceeded in near-quantitative yield. With acetone, an ene reaction occurred. The four-membered ring 1,2-oxastannacyclobutane obtained with benzaldehyde underwent a ring expansion with a second molecule of benzaldehyde to afford the six-membered ring dioxastannacyclohexane.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] | |||||||||||||||||||||||||