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Andreas Lindert

Bio: Andreas Lindert is an academic researcher from Michigan State University. The author has contributed to research in topics: Lithium & Alkylation. The author has an hindex of 5, co-authored 7 publications receiving 354 citations.

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TL;DR: In this article, the formation of polyalkylated products is a major source of difficulty in the alkylation of ketone enolates, and to some extent, this difficulty can be minimized by the use of lithium rather than sodium or potassium enolate.

12 citations


Cited by
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TL;DR: This work has reported several recently reported Cu-catalyzed C-H oxidation reactions that feature substrates that are electron-deficient or appear unlikely to undergo single-electron transfer to copper(II), and evidence has been obtained for the involvement of organocopper(III) intermediates in the reaction mechanism.
Abstract: The selective oxidation of C-H bonds and the use of O(2) as a stoichiometric oxidant represent two prominent challenges in organic chemistry. Copper(II) is a versatile oxidant, capable of promoting a wide range of oxidative coupling reactions initiated by single-electron transfer (SET) from electron-rich organic molecules. Many of these reactions can be rendered catalytic in Cu by employing molecular oxygen as a stoichiometric oxidant to regenerate the active copper(II) catalyst. Meanwhile, numerous other recently reported Cu-catalyzed C-H oxidation reactions feature substrates that are electron-deficient or appear unlikely to undergo single-electron transfer to copper(II). In some of these cases, evidence has been obtained for the involvement of organocopper(III) intermediates in the reaction mechanism. Organometallic C-H oxidation reactions of this type represent important new opportunities for the field of Cu-catalyzed aerobic oxidations.

1,129 citations

Journal ArticleDOI
Dieter Seebach1
TL;DR: There are six principal methods of umpolung: 1 2n-oxidation, heteroatom exchange and modification, homologation and its reversal, the cyclopropane “trick”, use of acetylenes, and redox reactions; under certain circumstances none of these techniques is necessary in cases where direct umpoline is possible.
Abstract: The past decade of organic chemistry may be charcterized as a period of violent development of new synthetic methods. This was accompained by a systematization of the analysis of synthetic problems (synthetic strategy). The planning of the synthesis of an organic target molecule is greatly facilitated by distinguishing between reagents X(C)n … with normal reactivity (acceptor properties at C1,3,5…, donor properties at X, C2,4…) and with reactivity umpolung (acceptor properties at X, C2,4…, donor properties at C1,3,5…). In this context, reactivity umpolung turned out to be useful as a heuristic principle, as a classification scheme, and as an aid for locating so-called strategic bonds (synthon, transform, and antithesis according to E. J. Corey). There are six principal methods of umpolung: 1 2n-oxidation, heteroatom exchange and modification, homologation and its reversal, the cyclopropane “trick”, use of acetylenes, and redox reactions; under certain circumstances none of these techniques is necessary in cases where direct umpolung is possible. Throughout the article, normal reactivity is indicated by green print; reactivity umpolung by red print.

968 citations

Patent
22 Mar 1995
TL;DR: The catalysts obtained from the components of the invention are particularly suitable for gas-phase polymerization processes as discussed by the authors, and are used for gas phase polymerization of olefins.
Abstract: Components of bimetallic catalysts for the polymerization of olefins comprising a compound of a transition metal M selected from Ti, V, Zr and Hf containing at least one M-π bond, a compound of Ti or V not containing metal-π bonds and a support comprising a magnesium halide. The catalysts obtained from the components of the invention are particularly suitable for gas-phase polymerization processes.

947 citations

Journal ArticleDOI
TL;DR: The Umpolung der Reaktivitat wurde als nutzliches heuristisches Prinzip, als Einteilungsschema und als Leitfaden zum Auffinden strategischer Bindungen erkannt (Synthon-, Transform-and Retrosynthesebetrachtungen nach Corey) as mentioned in this paper.
Abstract: In den letzten zehn Jahren haben sich die organisch-chemischen Synthesemethoden sturmisch entwickelt. Parallel dazu ist die Analyse synthetischer Probleme systematisiert worden (Syntheseplanung). Die Aufstellung eines Syntheseplans fur ein organisches Zielmolekul wird durch die Unterscheidung von Reagentien X(C)n … normaler Reaktivitat (Acceptoreigenschaften an C1, 3, 5 …, Donoreigenschaften an X, C2, 4…) und umgepolter Reaktivitat (Acceptoreigenschaften an X, C2, 4 …, Donoreigenschaften an C1, 3, 5 …) bedeutend erleichtert. Die Umpolung der Reaktivitat wurde als nutzliches heuristisches Prinzip, als Einteilungsschema und als Leitfaden zum Auffinden strategischer Bindungen erkannt (Synthon-, Transform- und Retrosynthesebetrachtungen nach Corey). Die Methoden der Umpolung lassen sich in sechs Gruppen einteilen: die 1, 2n-Oxidation, den Heteroatom-Austausch, die Homologisierung und ihre Umkehr, den Cyclopropan-„Trick”, die Verwendung von Acetylenen und die Redoxreaktionen; die in speziellen Fallen mogliche, direkte Umpolung kommt ohne diese Methoden aus. – In diesem Aufsatz wird die normale Reaktivitat durch grunen Druck, die umgepolte Reaktivitat durch roten Druck gekennzeichnet.

444 citations