The Role of Ate Complexes in Halogen(Metalloid)–Metal Exchange Reactions: A Theoretical Study

Boche, Gernot; Schimeczek, Michael; Ciosłowski, Jerzy; Piskorz, Pawel

doi:10.1002/(sici)1099-0690(199809)1998:9<1851::aid-ejoc1851>3.3.co;2-e

Cited by 20 publications

(31 citation statements)

References 7 publications

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“…Similarly, the Ph 2 S/Ph 2 Se/Ph 2 Te series is 1 : 10 4 : 10 14 (the PhI and Ph 2 Te rates are rather inexact extrapolations from DNMR work at temperatures below À 1008). There has been substantial computational effort at determining energies and structures of ate complexes of the main-group elements [30], and the calculated energies are consistent with our experimental data.…”

Section: Phàsàp-tol Phlisupporting

confidence: 75%

The Role of Ate Complexes in the Lithium-Sulfur, Lithium-Selenium and Lithium-Tellurium Exchange Reactions

Reich

Gudmundsson

Green

et al. 2002

HCA

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This paper is dedicated to Professor Dieter Seebach in honor of his 65th birthday Hypervalent ate complexes are presumptive intermediates in the metal-halogen, metal-tellurium, and related exchange reactions. The effect of o,o'-biphenyldiyl vs. diphenyl substitution on formation of tellurium ate complexes was studied by a kinetic technique and by NMR spectroscopy. Only a modest increase in the association constant (K ate ) was measured. When Li/M exchanges of o,o'-biphenyldiyl sulfides and selenides were made intramolecular by means of a m-terphenyl framework (12-S, 12-Se, 21), enormous increases (> 10 9 ) in the rate of Li/S and Li/Se exchange were observed compared to acyclic models. Apparently, these systems are ideally preorganized to favor the T-shaped geometry of the hypervalent intermediates. For the selenium systems, ate complex intermediates (20-Se, 26) were detected spectroscopically in THF-or THF/HMPA-containing solutions. A DNMR study showed that Li/Se exchange was substantially faster than exchange of the lithium reagents with the ate complex. Therefore, these ate complexes are not on the actual Li/Se exchange pathway.Introduction. ± The lithium-metalloid exchange reaction is the mildest and most general procedure for the preparation of organolithium reagents. The lithium-bromine [1] [2a] and lithium-iodine exchanges have been the most popular, but the reaction applies to many of the main-group third-, fourth-, and fifth-row elements. Tin [3a] [4], selenium (first studied by Seebach and Peleties [3b], and tellurium [3c] have been used extensively. The reaction fails with second-row CÀM bonds like those of chlorides, sulfides, and phosphines, except in exceptional circumstances, e.g., when there are no protons that can be metallated, when an unusually stable carbanion is being prepared, or when a strained ring is being cleaved [5] [6].Hypervalent ate complexes such as 1 ± 3 have been spectroscopically characterized and are likely intermediates in the degenerate phenyl-phenyl Li/I [7a] [7b] [8] [9], Li/Te [7b] [7c] [10a], and Li/Sn [7d] [11] [12] exchange reactions. Ate complexes of third-and even second-row metalloids Se, P, and Si can be detected in favorable structures, e.g., when the aryl groups are heavily substituted with electronegative halogen atoms (4, see [10b]) or when o,o'-biphenyldiyl ligands are present (5, see [13] and 6, see [14a]).

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Section: Phàsàp-tol Phlisupporting

confidence: 75%

The Role of Ate Complexes in the Lithium-Sulfur, Lithium-Selenium and Lithium-Tellurium Exchange Reactions

Reich

Gudmundsson

Green

et al. 2002

HCA

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“…The proposed mechanism for the formation of these products is outlined in Scheme . Organolithium 5 is assumed to be formed through an ate‐complex intermediate, favored by the presence of Br and O atoms in the substrate . The acyclic lithium intermediate 5 can undergone cyclization to the new lithiated cyclic intermediate 6 , which then yields the substituted 2,3‐dihydrobenzofuran 4 , by further reaction of 6 with the n ‐butyl bromide, previously generated by the halogen/metal exchange reaction.…”

Section: Resultsmentioning

confidence: 99%

Intramolecular carbolithiation‐cyclization‐electrophilic substitution: solvent effect and mechanistic study

Rodríguez

Nudelman

2013

J of Physical Organic Chem

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The intramolecular carbolithiation‐cyclization‐electrophilic substitution sequence proves to be a promising strategy for synthetic organic chemists. Our current research in this area focuses on the one‐pot halogen/lithium exchange of 2‐bromophenyl‐3‐phenylprop‐2‐enyl ether, followed by intramolecular carbolithiation, and trapping of the new lithiated cyclic intermediate by several electrophiles, affording 3‐substituted 2,3‐dihydrobenzofurans with some diastereoselectivity. Within this context, a study on the product distribution solvent dependence was carried out using different types of solvents, namely: polar coordinating, polar non‐coordinating, and non‐polar solvents. The results show that the coordinating features of the solvent affect specially the carbolithiation step, whereas the halogen/lithium exchange seems to be barely affected. Theoretical calculations were carried out to investigate the unexpected diastereoselectivity of the tandem reaction, where two stereocenters are generated. Insights gained from our mechanistic investigations enabled us to propose an inversion of configuration at the lithiated intermediate prior to the reaction, being the electrophile the likely cause for the observed distereoselectivity. Copyright © 2013 John Wiley & Sons, Ltd.

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“…Several reports suggest that the courses of the reactions are highly associated with the type of electrophile, which greatly impairs a study of this mechanism 13. Quantum‐chemical studies of Boche et al on methyl‐ate complexes suggest that ate complexes are pivotal intermediates in halogen–lithium exchange reactions with alkyllithium compounds 13e. Experimental and theoretical studies of Hoffmann et al as part of the synthesis of optically active alkylmagnesium compounds show that ate complexes are also involved in iodine–magnesium exchange reactions with alkylmagnesium compounds 13a–c…”

Section: Methodsmentioning

confidence: 99%

Enantiodivergence in the Reactions of a Highly Enantiomerically Enriched Silyllithium Compound with Benzyl Halides: Control of Inversion and Retention by Selection of Halide

et al. 2004

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The Role of Ate Complexes in Halogen(Metalloid)–Metal Exchange Reactions: A Theoretical Study

Cited by 20 publications

References 7 publications

The Role of Ate Complexes in the Lithium-Sulfur, Lithium-Selenium and Lithium-Tellurium Exchange Reactions

The Role of Ate Complexes in the Lithium-Sulfur, Lithium-Selenium and Lithium-Tellurium Exchange Reactions

Intramolecular carbolithiation‐cyclization‐electrophilic substitution: solvent effect and mechanistic study

Enantiodivergence in the Reactions of a Highly Enantiomerically Enriched Silyllithium Compound with Benzyl Halides: Control of Inversion and Retention by Selection of Halide

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