Double Diels-Alder Reaction Research Articles

Development of Functional Compounds Using Chemically Unstable Compounds Obtained from Medicinal Plants

Sulfur- or nitrogen-containing compounds from medicinal plants exhibit various biological activities such as anticancer potential. Developing efficient strategies to isolate or synthesize these compounds or their derivatives is a remarkable achievement. We have isolated several sulfur-containing compounds such as tetrahydro-2H-difuro[3,2-b:2',3'-c]furan-5(5aH)-one derivatives from Allium plants. We have devised a unique approach for the rapid preparation of thiopyranones using the regioselective sequential double Diels-Alder reaction; we used a naturally-occurring chemically-unstable intermediate such as thioacrolein, which is produced from allicin, a major component in garlic. The cytotoxicity of the synthetic thiopyranones against cancer stem cells (CSCs) was equal to or higher than that of (Z)-ajoene, the reference compound.

Beyond Diels-Alder: Domino reactions in furan-maleimide click networks

The furan-maleimide Diels-Alder chemistry has emerged as an important tool to design thermo-reversible click networks. This not only preserves the strong and robust properties of thermo-sets and rubbers, but also makes it possible to cleave crosslinks at non-degradative temperatures, or in other words to recycle them. In this work a new reaction is reported in furan-maleimide click networks, which is the Double-Diels-Alder reaction (DDA), also known as domino Diels-Alder. This forms extra linkages between Diels-Alder adducts and non-reacted furan groups and evidently leads to stronger materials, but also prevents efficient thermal (re)cycling. This work shows with nuclear magnetic resonance (NMR) characterization, differential scanning calorimetry (DSC) and rheology that the DDA reaction can occur both in intramolecular and intermolecular fashion, but also that it exhibits reversibility just like the regular Diels-Alder reaction. This reaction can be easily overlooked creating what at first sight might be inexplicable reactivity when analyzing the properties of furan-maleimide click networks.

The Pursuit of Perphenylterphenyls.

Tetradecaphenyl-p-terphenyl (2) was synthesized from 2,3,5,6-tetraphenyl-1,4-diiodobenzene (11) by two methods. Ullmann coupling of 11 with pentaphenyliodobenzene (9) gave compound 2 in 1.7 % yield, and Sonogashira coupling of 11 with phenylacetylene, followed by a double Diels-Alder reaction of the product diyne 12 with tetracyclone (6), gave 2 in 1.5 % overall yield. The latter reaction also gave the monoaddition product 4-(phenylethynyl)-2,2',3,3',4',5,5',6,6'-nonaphenylbiphenyl (13) in 4 % overall yield. The X-ray structures of compounds 2 and 13 show them to possess core aromatic rings distorted into shallow boat conformations. Density functional calculations indicate that these unusual structures are not the lowest energy conformations in the gas phase and may be the result of packing forces in the crystal. In addition, while uncorrected DFT calculations indicate that the strain energy in compound 2 is approximately 50 kcal/mol, dispersion-corrected DFT calculations suggest that it is essentially unstrained, due to compensating, favorable, intramolecular interactions of its many phenyl rings. An attempted synthesis of tetradecaphenyl-o-terphenyl (4) by reaction of diphenylhexatriyne (14) with three equivalents of tetracyclone at 350 °C gave only the diadduct 2-(phenylethynyl)-2',3,3',4,4',5,5',6,6'-nonaphenylbiphenyl (15) in 17 % yield. Even higher temperatures failed to produce 4 and lowered the yield of 15, perhaps due to rapid decomposition of the starting materials. Ullmann coupling of 3,4,5,6-tetraphenyl-1,2-diiodobenzene (16) and compound 9 also failed to give compound 4.

Construction of sulfur-containing compounds with anti-cancer stem cell activity using thioacrolein derived from garlic based on nature-inspired scaffolds.

Sulfur-containing compounds, such as cyclic compounds with a vinyl sulfane structure, exhibit a wide range of biological activities including anticancer activity. Therefore, the development of efficient strategies to synthesize such compounds is a remarkable achievement. We have developed a unique approach for the rapid and modular preparation of nature-inspired cyclic and acyclic sulfur-containing compounds using thioacrolein, a naturally occurring chemically unstable intermediate. We constructed thiopyranone derivatives through the regioselective sequential double Diels-Alder reaction of thioacrolein produced by allicin, a major component in garlic, and two molecules of silyl enol ether as the diene partner. The cytotoxicity toward cancer stem cells of the thiopyranones was equal to or higher than that of (Z)-ajoene (positive control) derived from garlic, and the thiopyranones had higher chemical stability than (Z)-ajoene.

Development and Applications of Double Diels‐Alder Reaction in Organic Synthesis

AbstractThe class of Double Diels‐Alder (DDA) reactions leading the targets concisely where numerous synthetic pursuits have been rewarded with conceptually novel and streamlined methods. After the tremendous development and discoveries in various Diels‐Alder reactions including its key role applications in many natural products syntheses, the DDA reaction is considered as a growing branch of Diels‐Alder reaction where two consecutive [4+2] cycloadditions trigger the streamlined construction of polycyclic and macrocyclic architectures. In light of the ever‐increasing importance of DDA reactions in chemical sciences, we review the comprehensive studies and recent advances in DDA reactions in organic synthesis. This review summarizes key achievements of DDA for the preparation of macrocyclic, bicyclic, heterocyclic, and polycyclic structures documented since its revelation in 1980 to 2020. Emphasis is put on the synthesis of various structural classes based on the selectivity of the DDA reaction.

Facile Synthesis of Aryl-Substituted Cycloarenes via Bismuth(III) Triflate-Catalyzed Cyclization of Vinyl Ethers

Cycloarenes are an essential class of polycyclic aromatic hydrocarbons with unique electronic structure, but their synthesis is very challenging. Herein, we report a facile synthetic strategy prima...

Facile One-Pot Synthesis and Crystal Structure of 2:1 Adducts of Myrcene (or Ocimene) with Benzoquinones

One-pot tandem oxidation and double Diels-Alder reaction of myrcene or ocimene with in situ generated 1,4-benzoquinone or 1,2-benzoquinone at 0°C for 1.5 h yielded polyalkylated 1,4,4a,5,8,8a,9a,10a-octahydro-9,10-anthracenediones and bis(alkylated) 9,10-phenanthrenedione respectively. The structure of novel bis-adduct from ocimene, (1R,4aR,5S,8aS,9aS,10aR)-rel- 1,4,4a,5,8,8a,9a,10a-octahydro-2,6-dimethyl-1,5-bis(3-methyl-2-buten-1-yl)-9,10-anthracenedione, was elucidated through single crystal X-ray analysis.

Revisiting Kekulene: Synthesis and Single-Molecule Imaging.

Four decades after the first (and only) reported synthesis of kekulene, this emblematic cycloarene has been obtained again through an improved route involving the construction of a key synthetic intermediate, 5,6,8,9-tetrahydrobenzo[m]tetraphene, by means of a double Diels–Alder reaction between styrene and a versatile benzodiyne synthon. Ultra-high-resolution AFM imaging of single molecules of kekulene and computational calculations provide additional support for a molecular structure with a significant degree of bond localization in accordance with the resonance structure predicted by the Clar model.

New Colorless and Transparent Poly(ether imide) Derived from a Biobased Plant Oil (Anethole): Synthesis and Properties

Starting from anethole, a biobased plant oil, a new monomer containing Wagner–Jauregg-type imide units was synthesized via cascade double Diels–Alder reaction. The reaction between the monomer and ...

Cascade Multiple Diels-Alder Reactions of Styrene Derivatives with Maleimide or Maleic Anhydride.

We developed novel one-pot multiple Diels-Alder reactions, which are frequently used in the construction of six-membered rings in functional molecular synthesis. We report triple and double Diels-Alder reactions with styrene derivatives, where the secondary Diels-Alder reaction takes place at a different position from that of the conventional Wagner-Jauregg reaction.

Crystal structure of 5,7,12,14-tetra-hydro-5,14:7,12-bis-([1,2]benzeno)-penta-cene-6,13-dione.

The lattice of 5,7,12,14-tetra-hydro-5,14:7,12-bis-([1,2]benzeno)-penta-cene-6,13-dione, C34H20O2, at 173 K has triclinic (P-1) symmetry and crystallizes with four independent half-mol-ecules in the asymmetric unit. Each mol-ecule is generated from a C17H10O substructure through an inversion center at the centroid of the central quinone ring, generating a wide H-shaped mol-ecule, with a dihedral angle between the mean planes of the terminal benzene rings in each of the two symmetry-related pairs over the four mol-ecules of 68.6 (1) (A), 65.5 (4) (B), 62.3 (9) (C), and 65.8 (8)° (D), an average of 65.6 (1)°. This compound has applications in gas-separation membranes constructed from polymers of intrinsic microporosity (PIM). The title compound is a product of a double Diels-Alder reaction between anthracene and p-benzo-quinone followed by de-hydrogenation. It has also been characterized by cyclic voltammetry and rotating disc electrode polarography, FT-IR, high resolution mass spectrometry, elemental analysis, and 1H NMR.

Mechanochemical Synthesis of Extended Iptycenes.

Iptycenes are intriguing compounds receiving considerable attention as a result of their rigid noncompliant three-dimensional architecture. The preparation of larger iptycenes is often problematic, as a result of their limited solubility and synthetic procedures involving multiple Diels-Alder reactions under harsh extended reaction conditions. We report a mechanochemical synthesis of structurally well-defined iptycenes through an iterative reaction sequence, wherein Diels-Alder reactions and a subsequent aromatization afford higher order iptycenes. We further report that double Diels-Alder reactions under solvent-free condition provide facile access to highly functionalized iptycenes with molecular weights over 2000 Da. Quartz crystal microbalance measurements reveal that these materials efficiently absorb the aromatic hydrocarbons benzene and toluene.

ChemInform Abstract: An Unexpected Double Diels—Alder Reaction of (E)‐2‐Bromo‐4‐aryl‐1,3‐pentadiene Involving [1,5]‐Hydrogen Migration and HBr Elimination: Synthesis of Bicyclo[2.2.2]octene Derivatives.

An unexpected double Diels-Alder (DDA) reaction of (E)-2-bromo-4-aryl-1,3-pentadiene was developed and resulted in a series of butterfly-like bicyclo[2.2.2]octene derivatives in moderate to good yields without the need for a metal catalyst. The proposed mechanism involves a [1,5]-sigmatropic hydrogen migration and HBr elimination. Through this decisive [1,5]-hydrogen shift step, the electronic properties and steric hindrance of the conjugated diene substrate are completely altered and the DDA reaction of this potential diene synthon is successfully achieved.

An unexpected double Diels-Alder reaction of (E)-2-bromo-4-aryl-1,3-pentadiene involving [1,5]-hydrogen migration and HBr elimination: synthesis of bicyclo[2.2.2]octene derivatives.

An unexpected double Diels-Alder (DDA) reaction of (E)-2-bromo-4-aryl-1,3-pentadiene was developed and resulted in a series of "butterfly-like" bicyclo[2.2.2]octene derivatives in moderate to good yields without the need for a metal catalyst. The proposed mechanism involves a [1,5]-sigmatropic hydrogen migration and HBr elimination. Through this decisive [1,5]-hydrogen shift step, the electronic properties and steric hindrance of the conjugated diene substrate are completely altered and the DDA reaction of this potential diene synthon is successfully achieved.

Synthesis of Bistetrahydroquinolines as Potential Anticholinesterasic Agents by Double Diels-Alder Reactions

The tetrahydroquinoline ring system is a unit found in many biologically active natural products and pharmacologically relevant therapeutic agents. A new series of bistetrahydroquinolines (bis-THQs) was synthesized using imino Diels-Alder reactions between dialdehydes, anilines and N-vinyl-2-pyrrolidone (NVP). The notable features of this procedure are mild reaction conditions, greater selectivity and good yields of products. In addition, the inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) of some selected derivatives is reported. The feasible binding modes of these active compounds, within AChE and BuChE binding sites, were predicted by molecular docking experiments and their binding affinity was estimated by means of free energy calculations through the MM-GBSA approximation.

One-pot thermally chemocontrolled double Diels–Alder strategies. A route to [4 + 2] functionalisation/[4 + 2] derivatization of C60

The one-pot double Diels–Alder reactions of 3,4-di(methylene)tetrahydrothiophene-1,1-dioxide using temperature as the only chemocontrol element are described. Zn-dust promoted the 1,4-debromination of 3,4-bis(bromomethyl)-2,5-dihydrothiophene-1,1-dioxide in 5-nonanone, under MW conditions, followed by a Diels–Alder reaction, an SO2 extrusion step and a second Diels–Alder reaction. This approach was applied successfully in double [4 + 2] cycloadditions using the same or two different dienophiles to afford the corresponding Diels–Alder products in excellent yields. An elegant and practical method for [4 + 2] functionalisation/[4 + 2] derivatization of C60 was achieved in a one-pot manner via the formation of a new reactive C66 dienic intermediate.

N-Alkyldinaphthocarbazoles, Azaheptacenes, for Solution-Processed Organic Field-Effect Transistors

Substituted N-alkyldinaphthocarbazoles were synthesized using a key double Diels-Alder reaction. The angular nature of the dinaphthocarbazole system allows for increased stability of the conjugated system relative to linear analogues. The N-alkyldinaphthocarbazoles were characterized by UV-vis absorption and fluorescence spectroscopy as well as cyclic voltammetry. X-ray structure analysis based on synchrotron X-ray powder diffraction revealed that the N-dodecyl-substituted compound was oriented in an intimate herringbone packing motif, which allowed for p-type mobilities of 0.055 cm(2) V(-1) s(-1) from solution-processed organic field-effect transistors.

Synthesis and Physicochemical Properties of Strong Electron Acceptor 14,14,15,15-Tetracyano-6,13-pentacenequinodimethane (TCPQ) Diimide

14,14,15,15-Tetracyano-6,13-pentacenequinodimethane (TCPQ) diimide, a new tetracyanoquinodimethane analogue with extended conjugation and imide substituents, was synthesized by double Diels–Alder reactions and a Knoevenagel condensation reaction. Experimental results showed that TCPQ diimide has a low LUMO energy level (–4.03 eV) and good solubility in organic solvents.

Improved Synthesis of Parent Fused 7-Oxanorbornenes

The synthesis of parent fused 7-oxanorbornenes 1 and 2 based on double Diels–Alder reaction of methyl propiolate with furan followed by saponification and reductive Barton decarboxylation is described.

Carbon-Carbon Double-Bond Isomerization and Diels-Alder Reaction of Dimethyl 5-Methylene-4-isopropylidene-2-cycloheptene-1,1-dicarboxylate with Dienophiles

Tricyclic compounds were obtained as a single diastereomer via carbon―carbon double-bond isomerization―Diels―Alder reaction of dimethyl 5-methylene-4-isopropylidene-2-cycloheptene-1,1-dicarboxylate with dienophiles under the catalysis of [RhCl(cod) 2 ] 2 /dppe/AgOTf. Further experiments provided the proof of isomerization of carbon―carbon double bond. Meanwhile a sequential double Diels―Alder reaction took place without carbon― carbon double-bond isomerization when 4-phenyl-4H-1,2,4-triazole-3,5-dione used as a dienophile.