Structure and reactivity of a sulfoximine‐stabilized chiral dilithiocarbanion

Müller, Jürgen; Neuburger, Markus; Zehnder, Margareta

doi:10.1002/hlca.19970800717

Cited by 60 publications

(24 citation statements)

References 51 publications

(4 reference statements)

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“…The α-Li centre in the monolithiated moiety interacts with neither the oxygen nor the nitrogen centres in the same unit but sits gauche with respect to these atoms and bonds, instead, to TMEDA and the O-centre of a dianionic sulfoximine unit (Figure 2a). Each of these dianions interact with both metal counterions via their deprotonated ortho positions -the corresponding the α-C lone pair in the dianion adopts a gauche conformation with respect to nitrogen and arene [60] two metals being stabilised by intramolecular N,O-coordination. The α-C lone pair in the dianion adopts a gauche conformation with respect to both nitrogen and deprotonated arene (Figure 2b).…”

Section: Solid-state Studiesmentioning

confidence: 99%

“…[57] The dilithiated sulfone 2-[(Me 3 Si) 2 C(Li·OEt 2 )SO 2 ]C 6 H 4 Li·OEt 2 (42) has been reported, wherein both O-directed ortholithiation (the solidstate structure reveals LiϪC ortho and LiϪO coordination) and deprotonation of the sulfone α-carbon are seen. [58] Reaction of racemic EtS(ϭO)(Ph)ϭNMe with nBuLi/ TMEDA in the presence of a trace oxide source [59] yields the heterochiral mixed α-mono-and α,orthodilithiated (43), [60] the solidstate structure of which reveals chiral resolution. Consequently, the aggregate is composed of two (S)-configured α-metallated sulfoximine monoanions and two (R)-configured α,orthometallated dianions.…”

Section: Solid-state Studiesmentioning

confidence: 99%

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The Directed Lithiation of Benzenoid Aromatic Systems

Wheatley

2003

Eur J Inorg Chem

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Directed metallation using organolithium bases is one of the best ways of regiospecifically elaborating aromatic systems and their substituents. For benzenoid arenes, deprotonation occurs at the ortho, lateral or peri positions. The reasons for each type of reaction will be considered in the context of the propensities of different directing groups for complex formation with the incoming organolithium base, acidification of the reactive site(s) and post‐reaction stabilisation of the metal ion(s). Discussion will concentrate on structural investigations, for the most part by single‐crystal X‐ray diffraction and/or by multinuclear NMR spectroscopy. Theoretical studies will also be incorporated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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Section: Solid-state Studiesmentioning

confidence: 99%

Section: Solid-state Studiesmentioning

confidence: 99%

The Directed Lithiation of Benzenoid Aromatic Systems

Wheatley

2003

Eur J Inorg Chem

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“…[29] Addition of MeI afforded nearly regioselectively the α,α-dimethylated S-tert-butyl-S-phenylsulfoximine 30 in high yield (85%). Such behaviour was unknown for sulfoximines but is not unusual for sulfones, where an α,ο-dilithiated species has also been observed that showed a similar reactivity with alkylhalides.…”

Section: Regio-and Diastereoselective Cyclisations With Biselectrophilesmentioning

confidence: 99%

“…[14,15,21] However, an attempt to crystallise a chiral dilithiomethane derivative was first undertaken by our group. [29] Dilithiation of 11 leads to a mixed aggregate containing mono-and dilithiated (Nmethyl)-S-ethyl-S-phenyl-sulfoximine units in a 2:2 ratio coordinated by 3 TMEDA ligands. Compound 12 crystallises in the space group C2/c and the unit cell contains 4 of the clusters together with 8 disordered TMEDA molecules ( Figure 5).…”

Section: Dilithiated Sulfoximinesmentioning

confidence: 99%

Chiral Dilithiomethane Derivatives: Structure Determination and Application in Stereoselective Reactions

Müller

2000

Eur. J. Inorg. Chem.

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The synthesis and X‐ray analysis of chiral dilithiomethane analogues derived from sulfoximines are presented. The structures of the sulfoximine‐stabilised mono‐ and dilithio salts have been compared and allow a rationalization of the second lithiation. Organophosphorus‐based dilithiomethane derivatives are also structurally described. The gas‐phase structures of N,S,S‐trimethylsulfoximine 19 and of its mono‐ and dilithiated isomers 20–21 were calculated by ab initio methods employing different levels of theory. For an application in asymmetric synthesis, the dilithiation of (N‐methyl)‐S‐ethyl‐S‐phenylsulfoximine (11) afforded a chiral dinucleophile that undergoes highly regio‐ and stereoselective alkylation reactions with electrophiles. The transmetallation of a chiral dilithiomethane reagent such as 14 with ClTi(OiPr)3 followed by addition of an aldehyde, constitutes a simple one‐pot process for the formation of (E)‐alkenylsulfoximines with excellent diastereoselectivity.

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“…In our inaugural experiment, we studied the reaction of 8a with the previously established geminal dianion 14, derived from bis-deprotonation of phenyl methyl sulfone (for the chemistry of α,α-dilithiosulfones, see refs. [15][16][17][18][19][20][21][22]. Remarkably, reaction of 8a with 14 afforded an angular phenylsulfonylmethyl product in 84% yield, as a single stereoisomer (Fig.…”

Section: Significancementioning

confidence: 99%

Stereospecific cis- and trans -ring fusions arising from common intermediates

Townsend

Ross

2014

Proc. Natl. Acad. Sci. U.S.A.

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Highly concise and stereospecific routes to cis and trans fusion, carrying various functionality at one of the bridgehead carbons, have been accomplished. Diels-Alder cycloaddition | cyclobutenone | angular methylation | mechanistic studies O ur group has been studying the synthetic utility of the DielsAlder (DA) reaction of the parent cyclobutenone, 2 (1). Recently reported results demonstrate that 2 is a highly reactive, endo-selective dienophile (Fig. 1, Eq. 1) (2). We have also developed a series of intramolecular Diels-Alder (IMDA) reactions, wherein the cyclobutenone component is tethered to various conjugated dienes (compare 4); cycloaddition of these substrates delivers adducts of the type 5, which can be readily converted to trans-fused systems bearing iso-DA patterns (Fig. 1, Eq. 2, 5→6) (3). Additionally, we have described the synthesis and DA cycloaddition of an even more powerful dienophile, 2-bromocyclobutenone (Fig. 1, Eq. 3, 7) (4). The direct adducts of this [4+2] reaction (compare 8) are readily converted to norcarane carboxylic acids (9) through exposure to hydroxide base. The research described herein was initially focused on efforts to add carbon-based nucleophiles to DA cycloadducts of the type 8. It might well have been expected that such reactions would give rise to products such as 10, wherein a ketone is appended to the junction of the norcarane system (Fig. 1, Eq. 4). Results and DiscussionWith a view toward accomplishing the transformation envisioned in Fig. 1, Eq. 4, compounds of the type 8 were exposed to methyllithium as described in Fig. 2. Interestingly, exposure of substrate 8a to the conditions shown led to an 81% yield of the angularly methylated product 11a, apparently unaccompanied by any part of the corresponding trans-fused diastereomer (Fig. 2, entry 1). Reactions conducted with related DA adducts 8b and 8c resulted in quite similar outcomes (Fig. 2, entries 2 and 3). Although we were confident that the products obtained were cisfused (Fig. 2, 11a-c), it was the synthesis of the rigorously assignable trans-fused product (vide infra) and its nonidentity with 11a that served to allow for sound assignment of the cisring fusion.An obvious mechanistic proposal to account for the formation of this structure envisions lithium-halogen exchange (5-8) leading to 12a and methyl bromide (Fig. 3). This step is followed by angular methylation (9-11) of 12a. It would not be surprising for such a reaction to have a very high preference for producing cis fusion. Clearly, a great deal of ring strain would be introduced in any transition state en route to trans-fused products.Whereas the enolate alkylation proposal is presumptive, several alternate formulations merited consideration. In principle, one can envision the possibility that lithium enolate 12a is not actually produced (perhaps due to ring strain). Rather, 11 (Fig. 3) arises from the merger of otherwise high-energy species en route to 12a and 12b. For instance, "radicaloid" (5) character could be generated at both the bridgehead ...

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Structure and reactivity of a sulfoximine‐stabilized chiral dilithiocarbanion

Cited by 60 publications

References 51 publications

The Directed Lithiation of Benzenoid Aromatic Systems

The Directed Lithiation of Benzenoid Aromatic Systems

Chiral Dilithiomethane Derivatives: Structure Determination and Application in Stereoselective Reactions

Stereospecific cis- and trans -ring fusions arising from common intermediates

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