Repetitive Diels-Alder Reactions Research Articles

ChemInform Abstract: 5,6,7,8-Tetramethylenebicyclo(2.2.2)oct-2-ene as “Bis(diene)” in Repetitive Diels-Alder Reactions.

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Inherently Chiral Molecular Clips: Synthesis, Chiroptical Properties, and Application to Chiral Discrimination

Inherently chiral molecular clips (MCs), pseudoenantiomeric anti-1 and anti-2, as well as mesoid syn-3, were synthesized by diastereodifferentiating repetitive Diels-Alder reactions of the achiral bisdienophile 6 with chiral diene 5 generated in situ from (-)-menthyl 3,4-bis(dibromomethyl)benzoate 4. These MCs were successfully separated by chiral HPLC to give optically active anti-1 and anti-2 and almost optically inactive syn-3. The structures of anti-1, anti-2, and syn-3 were assigned by high-resolution NMR and the absolute configurations of anti-1 and anti-2 were determined by the exciton-chirality method. Optically active anti-2 can serve as a chiral host. It binds the HCl adduct of D-tryptophan methyl ester (D-TrpOMeHCl) 3.5 times stronger than the L-enantiomer (KD/KL=3.5).

Molecular tweezers and clips as synthetic receptors. Molecular recognition and dynamics in receptor-substrate complexes.

The molecular tweezers (1, 2) and clips (3-7) containing naphthalene and benzene spacer units can be synthesized via repetitive Diels-Alder reactions by the use of a molecular "Lego" set consisting of bisdienophiles (8, 9, 14) and dienes (10, 13). The new receptors selectively bind electron-deficient neutral and cationic substrates in solution. Only the benzene-spaced tweezers form complexes with aliphatic substrates, whereas the other receptors bind aromatic substrates preferentially. HPLC studies with 1 and 2 chemically bonded to stationary phases give similar results for the heterogeneous systems. The formation of stable complexes between the water-soluble clip 5g and N-alkylpyridinium cations, such as N-methylnicotinamide and NAD(+), in aqueous solution illustrates the importance of the hydrophobic effect for arene-arene interactions. The dynamics of the complex formation and substrate mobility were investigated by the use of temperature-dependent liquid- and solid-state NMR spectroscopy. The electrostatic potential surface (EPS) of 1-7 is calculated to be surprisingly negative on the concave side of each molecule and, hence, complementary to the EPS of the electron-deficient substrates, suggesting that the attractive receptor-substrate interaction is here of predominantly electrostatic nature.

Control of viscosity through reversible addition of telechelics via repetitive Diels-Alder reaction in bulk

A synthetic approach towards reversible viscosity control through shifting the polymerization equilibrium was investigated. In model experiments the thermoreversible [4π+2π]-cycloaddition reaction between 3-hydroxymethylfuran (3) and ethyl trans-4,4,4-trifluorocrotonate (7) exhibited satisfactory reaction rates with no formation of side-products. Hence, the Diels-Alder reactive sites of these model compounds appeared suitable for the thermoreversible formation of polymers. The telechelic bisdiene α,ω-bis(3-furylmethyl)-pentaethyleneglycol (10) as well as the bisdienophile α,ωbis(trans-4,4,4-trifluorocrotonylethyl)-polyethyleneglycol (11) was synthesized. The reaction between 10 and 11 was free of side-reactions (1H-NMR, 300 MHz) in 12 cycles of both cycloaddition (50-80°C) and cycloreversion reactions (150°C) under inert conditions. Starting from a mixture of low viscosity, after every cycloaddition reaction, the viscosity increased, almost to the gel point. This thermoreversible reaction system therefore allows control of the viscosity of the mixture via its molecular weight, which was demonstrated by viscosity and rheological measurements.

Synthesis of Sterically Rigid Macrocycles by The Use of Pressure‐Induced Repetitive Diels–Alder Reactions

AbstractSyntheses of syn‐dimethanotetrahydroanthracene, ‐tetracene, and ‐pentacene derivatives 8a–d, 9a–d, and syn‐25 are described. Highly stereoselective, pressure‐induced Diels‐Alder reactions of the bis‐dienophiles 8a and/or 9a with the bis‐diene 7 lead to the sterically rigid macrocycles 1a, 2a, and 3a/3b, which have well defined cavities of different sizes.

Networks of Partially Hydrogenatedcis-1,4-Polybutadiene and ‘Rigid Rods’

Networks of 'flexible' and 'rigid' chains were synthesized. As 'flexible' component we have used different partially hydrogenated cis-1,4-polybutadiene. The 'rigid' component was synthesized from bis(1,2,4-triazoline-3,5-dione)s and biscyclohexadienes via repetitive Diels-Alder reaction. A slight excess of bis(1,2, 4-triazoline-3,5-dione)s leads to polymers with 1,2,4-triazoline-3,5-dione end groups, which can easily react with the partially hydrogenated cis-1,4-polybutadiene. The influence of the extent of hydrogenation and the amount of crosslinker on the mechanical and thermal behaviour is described.

The repetitive Diels-Alder reaction: A new approach to [60]fullerene maindashchain polymers

Maindashchain polymers with incorporated [60]fullerene units are accessible by reaction of buckminsterfullerene with functionalized bis -o- quinodimethanes . Cross linking can be effectively suppressed by carefully directed admixing of a mono -o- quinodimethane . The polymer 11(n) of high molecular weight and excellent solubility, consisting of 80 [60]fullerene units on the average, is affordable. This polymer can be processed to thin amorphous films of high quality by spin coating.

Synthesis of sterically rigid macrocycles by the use of pressure-induced repetitive Diels-Alder reactions

Syntheses of the syn-dimethanotetrahydroanthracene and -tetracene derivatives 2a– d and 6a, b are described. Highly stereoselective, pressure-induced repetitive Diels-Alder reactions of these bis-dienophiles with bis-diene 7 lead to the sterically rigid macrocycles 10a, 10d, 13a and 14a, b having well defined cavities of different size.

Stereoselectivity in the synthesis of polyacene derivatives by repetitive Diels-Alder reactions

The bisaryne generated from 1,4,5,8-tetramethyl- 2,3,6,7-tetrabromonaphthalene reacts with 2,5-dymethylfuran to give — through the intermediacy of the 1:1 adduct 1 — the 2:1 adducts 2, with the major isomer 2a, the one with the anti-configuration as revealed by X-ray crystallography and rationalised by molecular mechanics. Diels-Alder reactions of the anti-bisdienophile 2a with 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane proceed with complete treble diastereoselectivity to give only one 1:1 adduct 3 and a single 2:1 adduct 4.

Polymers containing silicon spiro centers

A novel silaspirotetraene, (all-E)-2,3,7,8-tetrakis[(trimethylsilyl)methylene]-5-silaspiro[4.4]-nonane (4), with orthogonal geometry has synthesized. By reaction of 4 as a bisdiene (AA type) in a repetitive Diels-Alder reaction under high pressure with a bisdienophile (BB type), a ribbon-type polymer (8) was obtained in which pentacene precursor units are separated by silicon spiro centers. To investigate possible aromatization sequences and to exclude structural defects of polymer 8, a model compound was synthesized. The silaspirotetraene 4 is a promising candidate for the development of structures with orthogonal subunits, resulting in polymers and model compound with high-spin character and, perhaps, ferromagnetic couplings

New ladder polymers via repetitive Diels-Alder reaction under high pressure

The synthesis of a new ladder-type polymer by repetitive Diels-Alder reaction is described. Exo-5,6,7,8-tetramethylenebicyclo[2.2.2]oct-2-ene was treated with 1,4:5,8-bisepoxy-9,10-dihexyl-1,4:5,8-tetrahydroanthracene (2) at high pressure (7-8 kbar). Under these conditions the formation of a ladder polymer was obtained. The influence of concentration, solvent, and temperature on the polymer-forming reaction is discussed. An attempt is made to solve the complex stereochemistry by the preparation of model compounds

Molecular LEGO. 1. Substrate-directed synthesis via stereoregular Diels-Alder oligomerizations

The diastereoselective synthesis and structural characterization of a wide range of wholly-synthesis cyclic and acyclic polyacene derivatives has been achieved. These novel compounds are notable for (i) their rigidity, (ii) their highly-ordered structures, and (iii) the high stereochemical precision which governs their formation. A key feature in the success of the synthetic methodology described is the development of a repetitive Diels-Alder reaction sequence in which three distinct levels of diastereoselectivity are expressed during each cycloaddition involving bisdiene and bisdienophilic building blocks

5,6,7,8‐Tetramethylenebicyclo[2.2.2]oct‐2‐ene as “Bis(diene)” in Repetitive Diels‐Alder Reactions

AbstractThe synthesis of ladder‐type oligomers by repetitive Diels‐Alder reactions is described. The title compound 1 has been treated with the “bis(dienophile)” 2 at high pressure (7.5 kbar). Under these conditions the formation of oligomers with up to 33 laterally anellated six‐membered rings has been achieved. An attempt has been made to analyze the complex stereochemistry of the cycloadditon by using the model compounds 5a, 5b.

1,2,5,6-Tetra-exo-methylenecynclooctane and [2.2]-(2,3)- Furanophane as bis-diene components in diels-alder reactions

Repetitive Diels-Alder reactions 1 of 1,2,5,6-tetra- exo-methylenecyclooctane ( 3) and [2.2]-(2,3)-furanophane ( 6) provide novel band-type structures. 3 and 6 differ significantly in the relative rate of the first and second cycloaddition.

ChemInform Abstract: Stereoregular Oligomerization by Repetitive Diels‐Alder Reactions.

ChemInform Abstract: Stereoregular Oligomerization by Repetitive Diels‐Alder Reactions.

Stereoregular Oligomerization by Repetitive Diels–Alder Reactions

Stereoregular Oligomerization by Repetitive Diels–Alder Reactions

Ribbon-shaped structures via repetitive Diels-Alder (DA) reaction. A polycatafusene

Preparation d'un poly derive de poly[(0,0,0,1,1,2,2) catafusene (0,0)] par reactions de Diels Alder multiples entre un diene bifonctionnel forme in situ et un dienophile bifonctionnel

ChemInform Abstract: Synthesis of Molecular Lines, Rigid Linear Molecules with Nanometer Scale Dimensions.

AbstractDiels‐Alder reaction of the bis(furo)anthraquinone (I) and the N‐aryl maleimide (II) gives a mixture of the mono‐ and bisadducts (III) and (IV) which are transformed into the linear polyacenequinone derivatives (V), (VII), and (VIII).

Synthesis of molecular lines, rigid linear molecules with nanometer scale dimensions

The synthesis of molecular 3.06, 5.28, and 7.50 nm lines, composed of polyacenequinone units, via repetitive Diels–Alder reactions is reported.

Repetitive Diels-Alder reactions for the growth of linear polyacenequinoid derivatives

Synthese en particulier d'heptacenetriquinone-5,18:7,16:9,14 et d'undecacenepentaquinone-5,26:7,24:9,22:11,20:13,18 a partir de derives d'ethano naphto furanne et de benzoquinones-1,4