PyBox–La(OTf)3-Catalyzed Enantioselective Diels–Alder Cycloadditions of 2-Alkenoylpyridines with Cyclopentadiene
Ontology highlight
ABSTRACT:
SUBMITTER: Wei H
PROVIDER: S-EPMC11243330 | biostudies-literature | 2024 Jun
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Metal nanoparticles are currently being employed as catalysts for a number of classical chemical transformations. In contrast, identification of novel reactions of nanoparticles, especially toward the synthesis of complex natural products and derivatives, is highly underdeveloped and represents a bourgeoning area in chemical synthesis. Herein, we report silica-supported silver nanoparticles as solid, recyclable catalysts for Diels-Alder cycloadditions of 2'-hydroxychalcones and dienes in high yield and turnover number. The use of silver nanoparticle catalysts is further demonstrated by the total synthesis of the cytotoxic natural product panduratin A employing a highly electron-rich dienophile and Lewis acid sensitive diene.
| S-EPMC2882859 | biostudies-literature
Project description:Fullerenes have potential applications in many fields. To reach their full potential, fullerenes have to be functionalized. One of the most common reactions used to functionalize fullerenes is the Diels-Alder cycloaddition. In this case, it is important to control the regioselectivity of the cycloaddition during the formation of higher adducts. In C60, successive Diels-Alder cycloadditions lead to the Th-symmetric hexakisadduct. In this work, we explore computationally using density functional theory (DFT) how the presence of a [10]cycloparaphenylene ring encapsulating C60 ([10]CPP⊃C60) affects the regioselectivity of multiple additions to C60. Our results show that the presence of the [10]CPP ring changes the preferred sites of cycloaddition compared to free C60 and leads to the formation of the tetrakisadduct. Somewhat surprisingly, our calculations predict formation of this particular tetrakisadduct to be more favored in [10]CPP⊃C60 than in free C60.
| S-EPMC9016765 | biostudies-literature
Project description:B3LYP/6-31G(d) density functional theory has been used to study Diels-Alder reactions of cyclopentadiene with alpha,beta-unsaturated aldehydes and ketones organocatalyzed by MacMillan's chiral imidazolidinones. Preferred conformations of transition structures and reaction intermediates have been located. The dramatically different reactivities and enantioselectivities exhibited by two similar chiral imidazolidinones are rationalized.
| S-EPMC3164120 | biostudies-literature
Project description:A new chiral Brønsted acid-catalyzed aza-Diels-Alder reaction of cyclic C-acylimines with cyclopentadiene has been developed. The reaction provides optically active aza-tetracycles in good yields with high diastereo- and enantioselectivities under mild reaction conditions.
| S-EPMC3511017 | biostudies-literature
Project description:The reactivities and π-facial stereoselectivities of Diels-Alder reactions of 5-substituted cyclopentadienes were studied using density functional theory. Burnell and co-workers previously showed that the π-facial selectivities result from the energies required to distort the reactants into the transition state geometries. We have discovered the origins of these distortions. C5-X σ-donors predistort the cyclopentadiene into an envelope conformation that maximizes the stabilizing hyperconjugative interaction between the C5-X σ-bond and the diene π-system. This envelope conformation geometrically resembles the anti transition state. To minimize the destabilizing effect of negative hyperconjugation, C5-X σ-acceptors predistort in the opposite direction toward an envelope geometry that resembles the syn transition state. We now show how hyperconjugative effects of the C5-X substituent influence the stereoselectivities and have developed a unified model rationalizing the stereoselectivities and reactivities of 5-substituted cyclopentadiene Diels-Alder reactions.
| S-EPMC6467786 | biostudies-literature
Project description:For over a century, the structures and reactivities of strained organic compounds have captivated the chemical community. Whereas triple-bond-containing strained intermediates have been well studied, cyclic allenes have received far less attention. Additionally, studies of cyclic allenes that bear heteroatoms in the ring are scarce. We report an experimental and computational study of azacyclic allenes, which features syntheses of stable allene precursors, the mild generation and Diels-Alder trapping of the desired cyclic allenes, and explanations of the observed regio- and diastereoselectivities. Furthermore, we show that stereochemical information can be transferred from an enantioenriched silyl triflate starting material to a Diels-Alder cycloadduct by way of a stereochemically defined azacyclic allene intermediate. These studies demonstrate that heteroatom-containing cyclic allenes, despite previously being overlooked as valuable synthetic intermediates, may be harnessed for the construction of complex molecular scaffolds bearing multiple stereogenic centres.
| S-EPMC6317513 | biostudies-literature
Project description:Macrocyclization can improve bioactive peptide ligands through preorganization of molecular topology, leading to improvement of pharmacologic properties like binding affinity, cell permeability, and metabolic stability. Here we demonstrate that Diels-Alder [4 + 2] cycloadditions can be harnessed for peptide macrocyclization and stabilization within a range of peptide scaffolds and chemical environments. Diels-Alder cyclization of diverse diene-dienophile reactive pairs proceeds rapidly, in high yield and with tunable stereochemical preferences on solid-phase or in aqueous solution. This reaction can be applied alone or in concert with other stabilization chemistries, such as ring-closing olefin metathesis, to stabilize loop, turn, and ?-helical secondary structural motifs. NMR and molecular dynamics studies of model loop peptides confirmed preferential formation of endo cycloadduct stereochemistry, imparting significant structural rigidity to the peptide backbone that resulted in augmented protease resistance and increased biological activity of a Diels-Alder cyclized (DAC) RGD peptide. Separately, we demonstrated the stabilization of DAC ?-helical peptides derived from the ER?-binding protein SRC2. We solved a 2.25 Å cocrystal structure of one DAC helical peptide bound to ER?, which unequivocally corroborated endo stereochemistry of the resulting Diels-Alder adduct, and confirmed that the unique architecture of stabilizing motifs formed with this chemistry can directly contribute to target binding. These data establish Diels-Alder cyclization as a versatile approach to stabilize diverse protein structural motifs under a range of chemical environments.
| S-EPMC7745206 | biostudies-literature
Project description:We have accomplished a parallel screen of cycloaddition partners for o-quinols utilizing a plate-based microwave system. Microwave irradiation improves the efficiency of retro-Diels-Alder/Diels-Alder cascades of o-quinol dimers which generally proceed in a diastereoselective fashion. Computational studies indicate that asynchronous transition states are favored in Diels-Alder cycloadditions of o-quinols. Subsequent biological evaluation of a collection of cycloadducts has identified an inhibitor of activator protein-1 (AP-1), an oncogenic transcription factor.
| S-EPMC3214659 | biostudies-literature
Project description: Not available
| S-EPMC2779767 | biostudies-literature
Project description:Ruthenium(II) polypyridyl complexes promote the efficient radical cation Diels-Alder cycloaddition of electron-rich dienophiles upon irradiation with visible light. These reactions enable facile [4 + 2] cycloadditions that would be electronically mismatched under thermal conditions. Key to the success of this methodology is the availability of ligand-modified ruthenium complexes that enable rational tuning of the electrochemical properties of the catalyst without significantly perturbing the overall photophysical properties of the system.
| S-EPMC3227774 | biostudies-literature