The synthesis and directed ortho-lithiation of 4-tert-butylsulfinyl[2.2]paracyclophane

Hitchcock, Peter B.; Rowlands, Gareth J.; Seacome, Richard J.

doi:10.1039/b509994c

Cited by 29 publications

(30 citation statements)

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“…Standard iron-catalysed bromination of 1 gave (±)-4-bromo[2.2]paracyclophane 3 in good yield [35–36]. Halogen-lithium exchange and addition to Ellman’s ( R )- tert -butyl tert -butanethiosulfinate [37] 4 furnished a 1 : 1.4 mixture of ( S p , R S )- 5 and ( R p , R S )- 5 in a combined 72% yield [33]. The two diastereoisomers are readily separable by standard column chromatography, with the diastereoisomer ( S p , R S )- 5 being eluted first.…”

Section: Resultsmentioning

confidence: 99%

“…As the sulfinylation reaction proceeds with inversion at sulfur, the two diastereoisomers only differ by the chirality of the [2.2]paracyclophane therefore allowing the facile resolution of the planar chirality. The assignment of configuration is based on a combination of X-ray studies [33,38], formation of all stereoisomers and analogy to our previous tolylsulfinyl chemistry [31,39]. …”

Section: Resultsmentioning

confidence: 99%

“…Secondly, the sulfinyl moiety permits further functionalisation of the [2.2]paracyclophane skeleton [33]. It is the latter reason that prompted the synthesis of the thiol via the tert -butyl derivative and not by direct sulfoxide-metal exchange; whilst this route would have delivered 2 more rapidly it would not have permitted elaboration of the [2.2]paracyclophane framework.…”

Section: Resultsmentioning

confidence: 99%

“…The only reported synthesis of enantiomerically pure [2.2]paracyclophane-4-thiol entails the palladium-mediated addition of triisopropylsilanethiol to a triflate formed from previously resolved ( R )-4-hydroxy[2.2]paracyclophane [18]. We are developing a ‘tool-box’ for the synthesis of enantiomerically enriched [2.2]paracyclophane derivatives based on the chemistry of [2.2]paracyclophane sulfoxides [15,31–33]. This methodology has allowed us to develop routes to enantiomerically pure 4-monosubstituted [2.2]paracyclophanes [31] along with a range of disubstituted derivatives [33].…”

Section: Introductionmentioning

confidence: 99%

“…We are developing a ‘tool-box’ for the synthesis of enantiomerically enriched [2.2]paracyclophane derivatives based on the chemistry of [2.2]paracyclophane sulfoxides [15,31–33]. This methodology has allowed us to develop routes to enantiomerically pure 4-monosubstituted [2.2]paracyclophanes [31] along with a range of disubstituted derivatives [33]. The basis of the strategy is the stereospecific introduction of a sulfoxide to [2.2]paracyclophane to give readily separable diastereoisomers, thus resolving the planar chirality [34].…”

Section: Introductionmentioning

confidence: 99%

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Enantiospecific synthesis of [2.2]paracyclophane-4-thiol and derivatives

Rowlands

Seacome²

2009

Beilstein J. Org. Chem.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Enantiospecific synthesis of [2.2]paracyclophane-4-thiol and derivatives

Rowlands

Seacome²

2009

Beilstein J. Org. Chem.

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Sulfur‐Bearing Lithium Compounds in Modern Synthesis

Ruano

Parra

Alemán

2014

Lithium Compounds in Organic Synthesis

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Sulfur functions have been widely used for the stabilization of lithium carbanions. Their different oxidation states determine a variety of mechanisms for such stabilization, mainly related with their electronic effects (−I and −M) and associative abilities and also with the relative position of sulfur with respect to the C-Li bond. As additional interest, the sulfur of some of these functions is a stable stereogenic center, and their interactions with prochiral lithium carbanions are able to control the stereochemical course of their reactions with electrophiles, which can be successfully used in asymmetric synthesis. Finally, the chemical versatility of the sulfur functions and their easy elimination under diverse conditions confer to the sulfur-stabilized lithium carbanions a very important role in modern synthetic chemistry. In this chapter, we have organized the information attending to the relative position of the carbanionic center with respect to the sulfur function (α-, β-, and γ-lithiation, see Figure 8.1). Each item has been subdivided according to the nature of the sulfur function stabilizing the carbanion. In this sense, sulfoxides, sulfones, and sulfoximines are the three main functions stabilizing any type of lithium-carbanions, but the thioethers have also been described as stabilizing in αand β-lithiation processes. The fragment connecting S and Li is always formed by carbon atoms, but N is present in some cases of γ-lithiation.This chapter covers the literature of the last 10-12 years concerning the preparation and main synthetic applications of the lithium carbanions stabilized by sulfur functions. In most of the cases, the information that appeared in this century helps understand the role of the sulfur functions in the stabilization of the lithium carbanions, and therefore we have only mentioned, as introduction, the seminal references in the field. However, in those cases where there are few references in the last decade and most of the information has been reported before 2000, we have included and briefly commented on the most significant contributions to be able to understand the interest of such stabilizing functions. During the last decade have appeared excellent revisions concerning the reactivity and structure of lithium carbanions [1], the use of different sulfur functions in asymmetric synthesis [2], as Lithium Compounds in Organic Synthesis: From Fundamentals to Applications, First Edition. Edited by Renzo Luisi and Vito Capriati.

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Selective and Practical Oxidation of Sulfides to Diastereopure Sulfoxides: A Combined Experimental and Computational Investigation

et al. 2013

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chloromethane or methanol), following the Curtin-Hammett principle, the favoured path is the pro-R channel (M1!TS!M2) affording the (R c ,R s )-2a' product species in agreement with the observed diastereoselectivity. The M1-M1' and TS-TS' energy gaps are actually determined by the difference in the hydrogen bond network that features the two species even if the approaching orientation of the two molecules is governed by the interactions between the p systems of oxidant and substrate aromatic rings. The diastereomeric ratio computed on the basis of the energy difference between TS and TS' (0.7 kcal mol À1 ) is 63:37, which must be compared to the experimental value 9:1. When we consider free energy differences (2.4 kcal mol À1 in vacuum and 2.9 kcal mol À1 in solution) this theoretical ratio becomes 85:15 and 89:11, respectively, in excellent agreement with the experimental value 9:1.

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The synthesis and directed ortho-lithiation of 4-tert-butylsulfinyl[2.2]paracyclophane

Abstract: The ortho-lithiation of one diastereoisomer of 4-tert-butylsulfinyl[2.2]paracyclophane is the key step to the synthesis of a range of 4,5-disubstituted [2.2]paracyclophane derivatives.

Cited by 29 publications

References 23 publications

Enantiospecific synthesis of [2.2]paracyclophane-4-thiol and derivatives

Enantiospecific synthesis of [2.2]paracyclophane-4-thiol and derivatives

Sulfur‐Bearing Lithium Compounds in Modern Synthesis

Selective and Practical Oxidation of Sulfides to Diastereopure Sulfoxides: A Combined Experimental and Computational Investigation

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