Dimetalation: The Acidity of Monometalated Arenes Towards Superbasic Reagents

Baston, Eckhard; Maggi, Raimondo; Friedrich, Kirstin; Schlosser, Manfred

doi:10.1002/1099-0690(200111)2001:21<3985::aid-ejoc3985>3.0.co;2-y

Cited by 35 publications

(18 citation statements)

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“…Preparation of 5-tert-butyl-bisimidazoline 7 4.3.1. Dimethyl 5-tert-butyl isophthalate (7b) 17 . A solution of 5-tertbutyl isophthalic acid (7a) (2.17 g, 9.75 mmol) and sulfuric acid (1 mL) in MeOH (20 mL) was refluxed for 2.5 h. After being cooled to room temperature, the reaction mixture was diluted with AcOEt and washed with 10% NaOH aq and brine.…”

Section: Nmr Experiments In Figs 2 Andmentioning

confidence: 99%

C3-Symmetric chiral trisimidazoline: the role of a third imidazoline and its application to the nitro Michael reaction and the α-amination of β-ketoesters

et al. 2011

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Section: Nmr Experiments In Figs 2 Andmentioning

confidence: 99%

C3-Symmetric chiral trisimidazoline: the role of a third imidazoline and its application to the nitro Michael reaction and the α-amination of β-ketoesters

et al. 2011

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“…Die Deprotonierungen verlaufen regioselektiv in 2-Position bzw. 2,6-Position, was einer verbesserten Synthesestrategie im Vergleich zu Metallierungen mit BuLi [3] oder der Superbase LIC-KOR [90] entspricht, die unselektiv Mischungen der 1-und 2-monosubstituierten Isomere sowie aller zehn möglichen disubsti-tuierten Isomere ergeben. In Einklang damit, dass der Metallierungsprozess, der zur Bildung von 84 führt, eine AMMZ-Reaktion ist -und nicht etwa eine Natriumaddition -, nimmt das Zn-Atom im Produkt die Position des abgespaltenen 2-Protons ein und liegt in der Ebene des Naphthylrings, während das Na-Atom eine lange, schwache h 2 -Wechselwirkung mit den 1-und 2-Positionen des Rings eingeht (Abbildung 8).…”

Section: Deprotonierungen Mit Aluminatenunclassified

Deprotonierende Metallierungen mit 'at‐Verbindungen: Synergie, Synthese und Strukturaufbau

Mongin²,

et al. 2007

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In der organischen Synthesechemie werden Monometallspezies wie Organolithiumverbindungen seit langem für Deprotonierungsreaktionen genutzt. In den letzten Jahren ist mit den 'at‐Komplexen eine neue Klasse von Metallierungsreagentien hinzugetreten, die das Syntheserepertoire metallorganischer Spezies ergänzt. Dank eines frei wählbaren Metallzentrums (Magnesium, Zink oder Aluminium), frei wählbarer Liganden (in Art und Anzahl) und eines frei wählbaren sekundären Metallzentrums (eines Alkalimetalls wie Lithium oder Natrium) sind 'at‐Komplexe äußerst vielseitige basische Reagentien, deren synergetische Reaktionsweisen mit den homometallischen Magnesium‐, Zink‐ oder Aluminiumverbindungen nicht beobachtet werden. Deprotonierungen mit metallorganischen 'at‐Komplexen haben neue Perspektiven in der organischen Chemie eröffnet, mit ungewöhnlichen Reaktivitäten und manchmal unvorhergesehenen Regioselektivitäten.

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“…Further useful dianions can be generated from ketones (C=C(OM)CM or C=C(OM)CCM) [138][139][140][141][142], carboxylic acids (C=C(OM) 2 ) [143][144][145], succinic acid derivatives ((C=C(OM)OR) 2 ) [146], alkynes (MC"CCM, MC"CC-OM) [147][148][149][150][151][152][153][154][155], imidazoles [156], thiophenes [157,158], b-alanine derivatives (MN-CC=C(OM)X) [159], 3-nitropropanoates [160,161], 3-hydroxypropanoates [162,163], 2-hydroxyethylsulfones [164,165], arenes [166][167][168], allenes [169], thioamides [170], and sulfonamides (MC-SO 2 NM [171]; R 2 NSO 2 -CM 2 [172]). If the nucleophilic sites in the polyanion have different chemical hardness, regioselective alkylation can be achieved by selecting a soft or a hard electrophile (second reaction, Scheme 5.13).…”

Section: 36mentioning

confidence: 99%

The Alkylation of Carbanions

Dörwald

2004

Side Reactions in Organic Synthesis

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The deprotonation of organic compounds by strong, non-nucleophilic bases followed by C-alkylation with a suitable electrophile has become one of the most predictable and straightforward methods for formation of C-C bonds. The popularity of this chemistry is also a consequence of the often-seen close resemblance of feasible structural modifications by a deprotonation/alkylation strategy to an unsophisticated retrosynthetic analysis of a given target compound. Other reactions, which involve, for instance, substantial rearrangement of the carbon framework (e.g. Cope rearrangement, fragmentations, ring contractions or enlargements) are usually more difficult to take into account during retrosynthetic analysis.LDA and related, sterically hindered, lithium dialkylamides, first investigated by Levine [1], have completely replaced the more nucleophilic sodium amide, which had been the base of choice for many years [2]. Because the reactivity of an organometallic compound depends to a large extent on its state of aggregation (i.e. on the solvent and on additives) and on the metal, transmetalation of the lithiated intermediates and the choice of different solvents and additives emerged as powerful strategies for fine-tuning the reactivity of these valuable nucleophiles.In this chapter the alkylation of carbanions with simple carbon electrophiles will be discussed, with special emphasis on the structure-reactivity relationship of the carbanion and on side reactions. In this context the term "carbanion" refers to an intermediate prepared by in-situ deprotonation of an organic compound, followed by optional cation exchange (transmetalation), which tends to be alkylated at carbon by soft electrophiles such as MeI or PhCHO. This type of reactivity is characteristic of enolates with an ionic M-O bond or for organometallic compounds with a strongly polarized or ionic M-C bond, M typically being an alkali metal, Mg, Cu, or Zn. Carbanions can, alternatively, also be prepared by halogen-metal exchange [3-8], sulfoxide-or sulfone-metal exchange [9-13], or by transmetalation of stannanes. The most suitable reagents for performing such metalating exchange reactions are organometallic compounds with a metal-bound secondary or tertiary alkyl group, such as tBuLi, sBuLi, iPr 2 Zn [14, 15], or iPrMgHal [6]. These reagents are thermodynamically less stable than organometallic compounds with primary alkyl 5 146 Scheme 5.1. Approximate relative rates of proton transfer in water at thermoneutrality (DpK a = 0) [35, 39, 51]. 147 Scheme 5.2. The effect of fluorine on the acidity of organic compounds [24, 62-65]. 148 Scheme 5.3. Dependence of the reactivity of carbanions on their basicity [68, 72-74]. Regioselectivity of Deprotonations and AlkylationsThe organic chemist is occasionally confronted with the problem that a compound has several differrent X-H groups of similar pK a . If only one of these is to be alkylated, one option would be to perform a regioselective deprotonation. This can sometimes be achieved by exploiting small differences be...

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Dimetalation: The Acidity of Monometalated Arenes Towards Superbasic Reagents

Cited by 35 publications

References 22 publications

C3-Symmetric chiral trisimidazoline: the role of a third imidazoline and its application to the nitro Michael reaction and the α-amination of β-ketoesters

C3-Symmetric chiral trisimidazoline: the role of a third imidazoline and its application to the nitro Michael reaction and the α-amination of β-ketoesters

Deprotonierende Metallierungen mit 'at‐Verbindungen: Synergie, Synthese und Strukturaufbau

The Alkylation of Carbanions

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