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Chiming Che - One of the best experts on this subject based on the ideXlab platform.
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dirhodium carboxylates catalyzed enantioselective coupling reactions of α diazophosphonates anilines and electron deficient aldehydes
Angewandte Chemie, 2012Co-Authors: Congying Zhou, Jingcui Wang, Jinhu Wei, Zhen Guo, Kamhung Low, Chiming CheAbstract:Chiral dirhodium carboxylate complexes ([Rh(2)(S-PTAD)(4)] or [Rh(2)(S-PTTL)(4)]) efficiently catalyze asymmetric three-component coupling reactions of α-diazophosphonates, anilines, and electron-deficient aldehydes to give α-amino-β-hydroxyphosphonates. The high level of enantiocontrol provides evidence for the intermediacy of metal-bound Ammonium Ylide in the product-forming step.
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a non cross linked soluble polystyrene supported ruthenium catalyst for carbenoid transfer reactions
Chemistry-an Asian Journal, 2008Co-Authors: Matthew Kwok Wai Choi, Congying Zhou, Qinghai Deng, Chiming CheAbstract:Ruthenium nanoparticles supported on non-cross-linked soluble polystyrene were prepared by reacting [RuCl2(C6H5CO2Et)](2) with polystyrene in open air. They effectively catalyze intra- and intermolecular carbenoid insertion into C-H and N-H bonds, alkene cyclopropanation, and Ammonium Ylide/[2,3]-sigmatropic rearrangement reactions. This supported ruthenium catalyst is much more reactive than [RuCl2(p-cymene)](2) and [Ru(Por)CO] for catalytic intermolecular carbenoid C-H bond insertion into saturated alkanes. By using alpha-diazoacetamide as a substrate for intramolecular carbenoid C-H insertion, the supported ruthenium catalyst can be recovered and reused for ten successive iterations without significant loss of activity.
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ruthenium porphyrin catalyzed tandem sulfonium Ammonium Ylide formation and 2 3 sigmatropic rearrangement a concise synthesis of platynecine
ChemInform, 2005Co-Authors: Congying Zhou, Philip Wai Hong Chan, Chiming CheAbstract:meso-Tetrakis(p-tolyl)porphyrinatoruthenium(II) carbonyl, [RuII(TTP)(CO)], can effect intermolecular sulfonium and Ammonium Ylide formation by catalytic decomposition of diazo compounds such as ethyl diazoacetate (EDA) in the presence of allyl sulfides and amines. Exclusive formation of [2,3]-sigmatropic rearrangement products (70−80% yields) was observed without [1,2]-rearrangement products being detected. The Ru-catalyzed reaction of EDA with disubstituted allyl sulfides such as crotyl sulfide produced an equimolar mixture of anti- and syn-2-(ethylthio)-3-methyl-4-pentenoic acid ethyl ester. The analogous “EDA + N,N-dimethylcrotylamine” reaction afforded a mixture of anti- and syn-2-(N,N-dimethylamino)-3-methyl-4-pentenoic acid ethyl esters with a diastereoselectivity of 3:1. The observed catalytic activity of [RuII(TTP)(CO)] for the Ylide [2,3]-sigmatropic rearrangement is comparable to the reported examples involving [Rh2(CH3CO2)4] and [Cu(acac)2] as catalyst. Similarly, cyclic sulfonium and Ammonium ...
Till Opatz - One of the best experts on this subject based on the ideXlab platform.
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ring expansion of 1 2 3 4 tetrahydroisoquinolines to dibenzo c f azonines an unexpected 1 4 sigmatropic rearrangement of nitrile stabilized Ammonium Ylides
Journal of Organic Chemistry, 2014Co-Authors: Julio Cesar Orejarena Pacheco, Till OpatzAbstract:When the products of a Strecker reaction of 1,2,3,4-tetrahydroisoquinolines with aromatic aldehydes are quaternized with alkyl triflates and subsequently treated with base, a ring expansion to 6,7,8,13-tetrahydro-5H-dibenzo[c,f]azonine-5-carbonitriles takes place. The nine-membered cyclic products can be obtained in good yields (78–89%) in a process involving the [1,4]-sigmatropic rearrangement of a nitrile-stabilized Ammonium Ylide. The reaction sequence provides a new, simple, and efficient method for the synthesis of these unusual N-heterocycles.
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Ring Expansion of 1,2,3,4-Tetrahydroisoquinolines to Dibenzo[c,f]azonines. An Unexpected [1,4]-Sigmatropic Rearrangement of Nitrile-Stabilized Ammonium Ylides
2014Co-Authors: Julio Cesar Orejarena Pacheco, Till OpatzAbstract:When the products of a Strecker reaction of 1,2,3,4-tetrahydroisoquinolines with aromatic aldehydes are quaternized with alkyl triflates and subsequently treated with base, a ring expansion to 6,7,8,13-tetrahydro-5H-dibenzo[c,f]azonine-5-carbonitriles takes place. The nine-membered cyclic products can be obtained in good yields (78–89%) in a process involving the [1,4]-sigmatropic rearrangement of a nitrile-stabilized Ammonium Ylide. The reaction sequence provides a new, simple, and efficient method for the synthesis of these unusual N-heterocycles
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a five step synthesis of tylophorine via a nitrile stabilized Ammonium Ylide
Journal of Organic Chemistry, 2012Co-Authors: Günther Lahm, Alexander Stoye, Till OpatzAbstract:The Stevens rearrangement of a nitrile-stabilized Ammonium Ylide is the key step of a very short and practical synthesis of the phenanthroindolizine alkaloid (±)-tylophorine. The method requires only five linear steps and is devoid of any protecting group manipulations.
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A Five-Step Synthesis of (±)-Tylophorine via a Nitrile-Stabilized Ammonium Ylide
2012Co-Authors: Günther Lahm, Alexander Stoye, Till OpatzAbstract:The Stevens rearrangement of a nitrile-stabilized Ammonium Ylide is the key step of a very short and practical synthesis of the phenanthroindolizine alkaloid (±)-tylophorine. The method requires only five linear steps and is devoid of any protecting group manipulations
Qinghai Deng - One of the best experts on this subject based on the ideXlab platform.
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a non cross linked soluble polystyrene supported ruthenium catalyst for carbenoid transfer reactions
Chemistry-an Asian Journal, 2008Co-Authors: Matthew Kwok Wai Choi, Congying Zhou, Qinghai Deng, Chiming CheAbstract:Ruthenium nanoparticles supported on non-cross-linked soluble polystyrene were prepared by reacting [RuCl2(C6H5CO2Et)](2) with polystyrene in open air. They effectively catalyze intra- and intermolecular carbenoid insertion into C-H and N-H bonds, alkene cyclopropanation, and Ammonium Ylide/[2,3]-sigmatropic rearrangement reactions. This supported ruthenium catalyst is much more reactive than [RuCl2(p-cymene)](2) and [Ru(Por)CO] for catalytic intermolecular carbenoid C-H bond insertion into saturated alkanes. By using alpha-diazoacetamide as a substrate for intramolecular carbenoid C-H insertion, the supported ruthenium catalyst can be recovered and reused for ten successive iterations without significant loss of activity.
Cm Che - One of the best experts on this subject based on the ideXlab platform.
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Ruthenium-porphyrin-catalyzed carbenoid transfer reactions
'Georg Thieme Verlag KG', 2010Co-Authors: Cm Che, Js Huang, Cy ZhouAbstract:Ruthenium-porphyrins are effective catalysts for a wide variety of carbenoid transfer reactions, such as alkene cyclopropanation, carbon-hydrogen, nitrogen-hydrogen, or sulfur-hydrogen (X-H, X = C, N, S) bond insertion, diazo coupling, carbonyl or azomethine Ylide formation/1,3-dipolar cycloaddition, and halonium, sulfonium, or Ammonium Ylide formation/[2,3]-sigmatropic rearrangement reactions. Extensive studies have demonstrated that ruthenium-porphyrins exhibit high stability, high product turnover numbers, and remarkable selectivity in catalytic carbenoid transfer reactions. The catalysis has been successfully applied to the synthesis of organic building blocks and natural products, and to the modification of peptides and proteins. 1 Introduction 2 Catalyst Types 3 Cyclopropanation Reactions 4 Carbon-Hydrogen, Nitrogen-Hydrogen, and Sulfur-Hydrogen Bond Insertion Reactions 5 Alkene Formation Reactions 5.1 Coupling of Diazo Compounds 5.2 Olefination of Aldehydes 6 Ylide Formation and Subsequent Reactions 6.1 Carbonyl Ylide Formation/1,3-Dipolar Cycloaddition 6.2 Azomethine Ylide Formation/1,3-Dipolar Cycloaddition 6.3 Halonium Ylide Formation/[2,3]-Sigmatropic Rearrangement 6.4 Sulfonium or Ammonium Ylide Formation/[2,3]-Sigmatropic Rearrangement 7 Comparison of (Carbene)ruthenium-Porphyrin Complexes with Iron and Osmium Analogues 8 Conclusion. © 2010 Georg Thieme Verlag Stuttgart · New York.link_to_OA_fulltex
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A non-cross-linked soluble polystyrene-supported ruthenium catalyst for carbenoid transfer reactions
Wiley-V C H Verlag Gmbh, 2008Co-Authors: Chi Mkw, Cy Zhou, Qh Deng, Cm CheAbstract:Ruthenium nanoparticles supported on non-cross-linked soluble polystyrene were prepared by reacting [RuCl2(C6H5CO 2Et)]2 with polystyrene in open air. They effectively catalyze intra-and intermolecular carbenoid insertion into C-H and N-H bonds, alkene cyclopropanation, and Ammonium Ylide/[2,3]-sigmatropic rearrangement reactions. This supported ruthenium catalyst is much more reactive than [RuCl2(p-cymene)]2 and [Ru(Por)CO] for catalytic intermolecular carbenoid C-H bond insertion into saturated alkanes. By using α-diazoacetamide as a substrate for intramolecular carbenoid C-H insertion, the supported ruthenium catalyst can be recovered and reused for ten successive iterations without significant loss of activity.Department of Applied Biology and Chemical Technolog
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A non-cross-linked soluble polystyrene-supported ruthenium catalyst for carbenoid transfer reactions
'Wiley', 2008Co-Authors: Qh Deng, Cy Zhou, Chi Mkw, Cm CheAbstract:Ruthenium nanoparticles supported on non-cross-linked soluble polystyrene were prepared by reacting [RuCl2(C6H5CO 2Et)]2 with polystyrene in open air. They effectively catalyze intra-and intermolecular carbenoid insertion into C-H and N-H bonds, alkene cyclopropanation, and Ammonium Ylide/[2,3]-sigmatropic rearrangement reactions. This supported ruthenium catalyst is much more reactive than [RuCl2(p-cymene)]2 and [Ru(Por)CO] for catalytic intermolecular carbenoid C-H bond insertion into saturated alkanes. By using α-diazoacetamide as a substrate for intramolecular carbenoid C-H insertion, the supported ruthenium catalyst can be recovered and reused for ten successive iterations without significant loss of activity. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.link_to_subscribed_fulltex
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Ruthenium porphyrin catalyzed tandem sulfonium/Ammonium Ylide formation and [2,3]-sigmatropic rearrangement. A concise synthesis of (±)-platynecine
'American Chemical Society (ACS)', 2004Co-Authors: Chan Pwh, Cy Zhou, Cm CheAbstract:meso-Tetrakis(p-tolyl)porphyrinatoruthenium(II) carbonyl, [Ru II(TTP)(CO)], can effect intermolecular sulfonium and Ammonium Ylide formation by catalytic decomposition of diazo compounds such as ethyl diazoacetate (EDA) in the presence of allyl sulfides and amines. Exclusive formation of [2,3]-sigmatropic rearrangement products (70-80% yields) was observed without [1,2]-rearrangement products being detected. The Ru-catalyzed reaction of EDA with disubstituted allyl sulfides such as crotyl sulfide produced an equimolar mixture of anti- and syn-2-(ethylthio)-3-methyl-4- pentenoic acid ethyl ester. The analogous "EDA + N,N- dimethylcrotylamine" reaction afforded a mixture of anti- and syn-2-(N,N-dimethylamino)-3-methyl-4-pentenoic acid ethyl esters with a diastereoselectivity of 3:1. The observed catalytic activity of [Ru II(TTP)(CO)] for the Ylide [2,3]-sigmatropic rearrangement is comparable to the reported examples involving [Rh2(CH 3CO2)4] and [Cu(acac)2] as catalyst. Similarly, cyclic sulfonium and Ammonium Ylides can be produced by intramolecular reaction of a diazo group tethered to allyl sulfides and amines under the [RuII-(TTP)(CO)]-catalyzed reaction conditions. The subsequent [2,3]-sigmatropic rearrangement of the cyclic Ylides furnished 2-allyl-substituted sulfur and nitrogen heterocycles in good yields (>90%). By employing [RuII(TTP)(CO)] as catalyst, the cyclic Ammonium Ylide [2,3]-sigmatropic rearrangement reaction was successfully applied for the total synthesis of (±)-platynecine starting from cis-2-butenediol.link_to_subscribed_fulltex
Albert Padwa - One of the best experts on this subject based on the ideXlab platform.
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an approach toward isoindolobenzazepines using the Ammonium Ylide stevens 1 2 rearrangement sequence
Journal of Organic Chemistry, 2001Co-Authors: Albert Padwa, L S Beall, Cheryl K Eidell, Kimberly J WorsencroftAbstract:Ammonium Ylides derived from the Cu(II)-catalyzed decomposition of α-diazo carbonyls tethered to tertiary amines underwent a benzylic Stevens [1,2]-rearrangement to give tetrahydroisoquinolines or benzazepines containing fused five-membered rings, a feature found in the cephalotaxus alkaloids. Model studies were also carried out toward the synthesis of lennoxamine, a member of the isoindolobenzazepine family of alkaloids. The approach utilized is based on the Rh(II)-catalyzed reaction of an α-diazo carbonyl compound containing an amido group in the γ-position. Treatment of several N,N-dialkyl-substituted amido diazo-esters with Rh2(OAc)4 in benzene at 80 °C in the presence of several dienophiles gave [4 + 2]-cycloadducts derived from the Diels−Alder reaction of a transient α-amino isobenzofuran intermediate. In the absence of an external trapping agent, no rearranged product derived from an Ammonium Ylide intermediate could be detected in the crude reaction mixture. In contrast to this result, reaction of...
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an approach to the cephalotaxine ring skeleton using an Ammonium Ylide stevens 1 2 rearrangement
Tetrahedron Letters, 1998Co-Authors: Scott L. Beall, Albert PadwaAbstract:Abstract Ammonium Ylides derived from the Cu(II)-catalyzed decomposition of α-diazo carbonyls tethered to tertiary amines underwent a benzylic Stevens [1, 2]-rearrangement to give tetrahydroisoquinolines or benzazepines containing fused five-membered rings, a feature found in the cephalotaxus and lycorane alkaloids.
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An Approach to the Cephalotaxine Ring Skeleton Using an Ammonium Ylide/Stevens [1,2]-Rearrangement
1998Co-Authors: Scott L. Beall, Albert PadwaAbstract:Abstract: Ammonium Ylides derived from the Cu(lI)-catalyzed decomposition fct-diazo carbonyls tethered to tertiary amines underwent a benzylic Stevens [1,2J-rearrangement to give tetrahydroisoquinolines or benzazepines containing fused five-membered rings, a feature found in the cephalotaxus and lycorane alkaloids. © 1998 Elsevier Science Ltd. All rights reserved. The tandem Ammonium Ylide generation/rearrangement sequence represents an effective method for the preparation of nitrogen-containing heterocycles. 1 A typical example involves the ring expansion reaction of a spirocyclic Ammonium Ylide such as 3 which has been nicely exploited for the synthesis of a number of alkaloids. Thus, the key step in West and Naidu's enantioselective synthesis of (-)-epilupinine 2 involved the Ammonium Ylide-Stevens [1,2]-rearrangement of the (L)-proline derivative 1which furnished the advanced intermediate 4 in 84 % yield and with 76 % ee. Starting from a related (L)-proline derivative 2 (R=vinyl), Clark and Hodgson synthesized the CE ring system 5 in their approach to the Mazamine A ring skeleton via an Ammonium Ylide-[2,3]-sigmatropic rearrange-ment (Scheme 1).3'