Organocatalytic Desymmetrization Prompts Central-to-Planar Chirality Transfer to [2.2]Paracyclophanes

Dočekal, Vojtěch; Koucký, Filip; Císařová, Ivana; Veselý, Jan

doi:10.26434/chemrxiv-2023-fkvmc

Cited by 3 publications

(3 citation statements)

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“…Typically, enantiomerically pure [2.2]paracyclophanes are produced either by resolution of diastereomeric derivatives , or by kinetic resolution. − In recent years, new approaches using desymmetrization or dynamic kinetic resolution have been developed (Scheme B). These include desymmetrization of meso -diformyl[2.2]paracyclophanes by oxidation or reduction and of diamido[2.2]paracyclophanes by asymmetric electrophilic substitution …”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…9−12 In recent years, new approaches using desymmetrization or dynamic kinetic resolution have been developed (Scheme 1B). These include desymmetrization of meso-diformyl [2.2]paracyclophanes by oxidation 13 or reduction 14 and of diamido [2.2]paracyclophanes by asymmetric electrophilic substitution. 9 In this study, we examined whether the enantioselective reaction of donor/acceptor carbenes with paracyclophanes would result in the ready generation of novel paracyclophane derivatives.…”

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Rhodium(II)-Catalyzed Asymmetric Cyclopropanation and Desymmetrization of [2.2]Paracyclophanes

Ly,

Bacsa,

Davies

2024

ACS Catal.

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Chiral [2.2]paracyclophane derivatives are of considerable interest because of their potential in asymmetric catalysis and the development of chiral materials. This study describes the scope of rhodium-catalyzed reactions of aryldiazoacetates with [2.2]paracyclophanes. The reaction with the parent [2.2]paracyclophane resulted in cyclopropanation at two positions, the ratio of which is catalyst-controlled. Because of the strain in the system, one of the cyclopropanes exists primarily as the norcaradiene structure, whereas the other preferentially exists as the cycloheptatriene conformer. In contrast, the reaction with [3.3]paracyclophane results in benzylic C−H functionalization. The reactions with substituted [2.2]paracyclophanes using chiral catalysts can result in either kinetic resolution or desymmetrization. The Rh 2 (S-p-PhTPCP)] 4 -catalyzed reaction of monosubstituted paracyclophanes results in kinetic resolution with a selectivity (s) factor of up to 20, whereas reactions on C 2v -symmetric disubstituted [2.2]paracyclophanes with Rh 2 (S-TPPTTL) 4 [TPPTTL = 2-(1,3-dioxo-4,5,6,7-tetraphenylisoindolin-2-yl)-3,3-dimethylbutanoate] results in effective desymmetrization to form cycloheptatriene-incorporated paracyclophanes in 78−98% ee.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Rhodium(II)-Catalyzed Asymmetric Cyclopropanation and Desymmetrization of [2.2]Paracyclophanes

Ly,

Bacsa,

Davies

2024

ACS Catal.

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Organocatalytic desymmetrization provides access to planar chiral [2.2]paracyclophanes

Dočekal,

Koucký,

Císařová

et al. 2024

Nat Commun

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Planar chiral [2.2]paracyclophanes consist of two functionalized benzene rings connected by two ethylene bridges. These organic compounds have a wide range of applications in asymmetric synthesis, as both ligands and catalysts, and in materials science, as polymers, energy materials and dyes. However, these molecules can only be accessed by enantiomer separation via (a) time-consuming chiral separations and (b) kinetic resolution approaches, often with a limited substrate scope, yielding both enantiomers. Here, we report a simple, efficient, metal-free protocol for organocatalytic desymmetrization of prochiral diformyl[2.2]paracyclophanes. Our detailed experimental mechanistic study highlights differences in the origin of enantiocontrol of pseudo-para and pseudo-gem diformyl derivatives in NHC catalyzed desymmetrizations based on whether a key Breslow intermediate is irreversibly or reversibly formed in this process. This gram-scale reaction enables a wide range of follow-up derivatizations of carbonyl groups, producing various enantiomerically pure planar chiral [2.2]paracyclophane derivatives, thereby underscoring the potential of this method.

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Synthesis of Three-Dimensional Benzophenone Analogues Based on a [2.2]Paracyclophane Scaffold

Benedetti,

Wu,

Micouin

2024

Synlett

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Herein, we report the synthesis of functionalized three-dimensional benzophenone analogues derived from [2.2]paracyclophane (pCp). The potential use of these compounds as photocatalysts is disclosed. Benzophenone and its derivatives are well-known photoactive compounds that have been extensively employed over the years as catalysts to promote a variety of transformations activated by light. The development of differently substituted three-dimensional versions of such compounds may significantly expand the range of applications of the molecules in photocatalysis. Exploitation of the planar chirality of substituted paracyclophanes could also lead to significant innovations in different fields. pCp-based benzophenone derivatives incorporating reactive ester or amide functions at their pseudo-gem position have been successfully prepared in a selective manner. Examples of both racemic and enantiopure compounds are reported. As proof of concept, the catalytic activity of the newly synthesized molecules has been compared to that of benzophenone in a known photooxidation reaction.

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Organocatalytic Desymmetrization Prompts Central-to-Planar Chirality Transfer to [2.2]Paracyclophanes

Cited by 3 publications

References 49 publications

Rhodium(II)-Catalyzed Asymmetric Cyclopropanation and Desymmetrization of [2.2]Paracyclophanes

Rhodium(II)-Catalyzed Asymmetric Cyclopropanation and Desymmetrization of [2.2]Paracyclophanes

Organocatalytic desymmetrization provides access to planar chiral [2.2]paracyclophanes

Synthesis of Three-Dimensional Benzophenone Analogues Based on a [2.2]Paracyclophane Scaffold

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