Design, classification, and strategies of synthesis of modular bidentate ligands based on aryl[2.2]paracyclophane backbone

Rozenberg, V. I.; Zhuravsky, R. P.; Сергеева, Е. В.

doi:10.1002/chir.20223

Cited by 28 publications

(13 citation statements)

References 33 publications

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“…17- 19 The procedure, which we have developed ear lier 18, 19 for the resolution of bromophenol 9 into enanti omers, also involves the synthesis and chromatographic separation of its esters with (1S) (-) camphanic acid fol lowed by hydrolysis of individual diastereomers.…”

Section: Resultsmentioning

confidence: 99%

Planar chiral hydroxy derivatives of [2.2]paracyclophane as auxiliaries for asymmetric allylboration

et al. 2007

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Allylboronic esters with various structures were synthesized for the first time based on [2.2]paracyclophane derivatives containing one or two hydroxy groups. It was demonstrated that these esters can be used as chiral inductors in the asymmetric allylboration of benzalde hyde. The highest enantiomeric excess of 1 phenylbut 3 en 1 ol (60%) was achieved in the reactions with acyclic bis O,O´ (paracyclophanyl) allylboronates based on (S) 4 hydroxy and (S) 12 bromo 4 hydroxy[2.2]paracyclophanes. (S) 4 Hydroxy[2.2]paracyclophane was studied by X ray diffraction.The allylboration of aldehydes is one of the most widely used approaches to the stereoselective C-C bond forma tion. 1-4 Generally, enantiomerically pure compounds (diols, diamines, sulfamides, and amino alcohols) pos sessing central 4 or (more rarely) axial chirality 5 are used for the design of reagents for the asymmetric allylboration.Earlier, 6,7 we have demonstrated for the first time that planar chiral [2.2]paracyclophane derivatives can be used in this reaction. For example, diastereomerically pure diallylborinate 2 was synthesized starting from 4 acetyl[2.2]paracyclophane (1) 8,9 (Scheme 1).Compound 2 was used in the allylboration of 4 for myl[2.2]paracyclophane (4) (de of rel (R p ,R) 4 (1 hydr oxybut 3 enyl)[2.2]paracyclophane (5) 50%) and benz aldehyde (6) (ee of 1 phenylbut 3 en 1 ol (7) was 18%). Homoallylic alcohol 3 produced in the reaction is a re cyclable auxiliary because it again gives ester 2 in the reaction with triallylborane (see Scheme 1).In alcohol 3, the hydroxy group is two bonds from the paracyclophane moiety. In the present study, we investi gated the influence of the distance between the functional group and the paracyclophane moiety on the stereochemi cal result of asymmetric allylboration of benzaldehyde. For this purpose, we examined for the first time the possi bility of designing reagents for the asymmetric allyl boration based on chiral phenols, viz., (S) 4 hydr oxy[2.2]paracyclophane (8) and (S) 12 bromo 4 hydr oxy[2.2]paracyclophane (9), in which the hydroxy group is directly fixed in the aromatic ring of [2.2]paracyclo phane.An important feature, which distinguishes phenols 8 and 9 from alcohol 3 containing two stereogenic centers, is that they contain only one (planar) chirality center, which eliminates the question about the possible coop erative effect of the planar and central chirality in the asymmetric process. Results and DiscussionSynthesis of starting phenols 8 and 9. Racemic phenol 8 was synthesized according to a known procedure. 10 To synthesize its enantiomers, we have developed 11-14 a pro cedure for the resolution of rac 8 into enantiomers through esters with (1S) (-) camphanic acid 10 (Scheme 2). 15, 16 Diastereomeric esters 10 were separated by fractional crystallization 15 followed by the preparative separation of the mother liquor by silica gel column chromatography. 16 In the present study, we improved the procedure for the isolation of enantiomers of phenol 8 from diastereo merically pure esters by us...

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Section: Resultsmentioning

confidence: 99%

Planar chiral hydroxy derivatives of [2.2]paracyclophane as auxiliaries for asymmetric allylboration

et al. 2007

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“…A Suzuki coupling of enantiopure ( S P )‐ 20 with 2‐hydroxyphenyl boronic acid ( 21 ) gave the diol ( S P )‐ 22 in 70% yield (Scheme ). This compound has been mentioned in the literature several times,27–29 but no characterization has been published so far.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and application of the first planar chiral strong brønsted acid organocatalysts

Enders¹,

Ludwig²,

Raabe³

2012

Chirality

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The synthesis of planar chiral strong Brønsted acid organocatalysts derived from [2.2]paracyclophane is described. Resolution was accomplished according to a modified protocol involving pseudo-ortho-substituted [2.2]paracyclophane-based sulfoxides for the synthesis of three new sulfonic acids. The first planar chiral phosphoric acid diester was obtained from the corresponding phenyl-substituted diol derived from enantiopure 4-bromo-12-hydroxy [2.2]paracyclophane. These new classes of catalysts were tested in an enantioselective Friedel-Crafts reaction as well as in a direct asymmetric Mannich reaction and gave yields of up to 93% and ee-values of up to 38%.

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“…Three ideas guided our thinking; we knew that the formyl group was readily introduced in a controlled manner through either the Rieche formylation 17,43 or nucleophilic attack on a formyl amide. 23,25,44 Secondly, the formyl group provides a means to resolve the planar chirality of [2.2]paracyclophane as demonstrated by Bräse's recent chemistry. 43,45 Finally there was literature precedent to suggest that an aldehyde could be transformed to an amine through the intermediacy of an oxime and/or hydroxamic acid.…”

Section: Scheme 1 Optimisation Of Copper-mediated Aminationmentioning

confidence: 99%

The synthesis of substituted amino[2.2]paracyclophanes

et al. 2016

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Two methodologies for the formation of substituted amino[2.2]paracyclophane derivatives were developed. The first involves the direct amination of bromo[2.2]paracyclophanes with sodium azide. This permits the synthesis of simple mono- and disubstituted derivatives but fails to give sterically congested pseudo-gem derivatives. A 'one-pot' oxidation-Lossen rearrangement of [2.2]paracyclophane oximes provides access to a range of amino[2.2]paracyclophanes including the most efficient synthesis of the pseudo-gem planar chiral amino acid yet reported.

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Design, classification, and strategies of synthesis of modular bidentate ligands based on aryl[2.2]paracyclophane backbone

Cited by 28 publications

References 33 publications

Planar chiral hydroxy derivatives of [2.2]paracyclophane as auxiliaries for asymmetric allylboration

Planar chiral hydroxy derivatives of [2.2]paracyclophane as auxiliaries for asymmetric allylboration

Synthesis and application of the first planar chiral strong brønsted acid organocatalysts

The synthesis of substituted amino[2.2]paracyclophanes

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