scholarly journals Maleimide Functionalized Siloxane Resins

1999 ◽  
Vol 576 ◽  
Author(s):  
R. M. Shaltout ◽  
D. A. Loy ◽  
D. R. Wheeler
Keyword(s):  
Diels Alder ◽  
Inorganic Filler ◽  
Side Reactions ◽  
Inorganic Component ◽  
New Class ◽  
Silicon Alkoxides ◽  
Filler Phase ◽  
Alder Adduct ◽  
Organic Monomer

ABSTRACTIn-situ filling through hydrolysis and condensation of silicon alkoxides dissolved into polymers has been utilized to generate nanocomposites in which the filler phase can be intimately associated with the polymer on relatively small length scales. One problem of the method has been achieving useful fill volumes without bulk phase separation of the growing inorganic component from the polymer. In this paper, we describe the preparation of a new class of nanocomposite materials in which the inorganic filler phase is pre-assembled before copolymerization with an organic monomer. Maleimide monomers, prepared from alkoxysilylpropyl amines and maleic anhydride, were protected against side reactions by forming the oxonorbornene Diels-Alder adduct with furan. The monomers were then reacted under solgel conditions to form oligomers or polymers making up the filler phase. The material was activated by thermal deprotection of the maleimide and reacted with organic monomers or polymers to form the filled nanocomposite.

Transparent silica gel–PMMA composites

1989 ◽  
Vol 4 (4) ◽  
pp. 1018-1026 ◽  
Author(s):  
E. J. A. Pope ◽  
M. Asami ◽  
J. D. Mackenzie
Keyword(s):  
Compressive Strength ◽  
Refractive Index ◽  
Polymer Composites ◽  
Silica Gel ◽  
Vickers Hardness ◽  
Modulus Of Rupture ◽  
New Class ◽  
Abrasion Rate ◽  
Organic Monomer

Transparent silica gel–polymer composites have been prepared by the impregnation of porous gels with organic monomer and polymerization in situ. The relative amount of each phase was adjusted by varying the porosity of the silica gel prior to impregnation. These materials constitute a new class of transparent composites. Properties, such as density, refractive index, modulus of rupture, compressive strength, abrasion rate, and Vickers hardness, have been measured over the compositional range of 100% silica to 100% polymethyl methacrylate (PMMA).

Properties of Transparent Silica Gel - Pmma Composites

1988 ◽  
Vol 132 ◽  
Author(s):  
Edward J. A. Pope ◽  
Minuo Asami ◽  
John D. Mackenzie
Keyword(s):  
Polymer Composites ◽  
Silica Gel ◽  
Porous Silica ◽  
Silica Gels ◽  
New Class ◽  
Transparent Composites ◽  
Organic Monomer

ABSTRACTTransparent silica gel - polymer composites have been prepared by the impregnation of porous silica gels with fluid organic monomer followed by in situ polymerization. These materials constitute an entirely new class of transparent composites.

scholarly journals Lithium-mediated Ferration of Fluoroarenes

2020 ◽  
Vol 74 (11) ◽  
pp. 866-870
Author(s):  
Lewis C. H. Maddock ◽  
Alan Kennedy ◽  
Eva Hevia
Keyword(s):  
Hydrogen Atom ◽  
Organometallic Chemistry ◽  
Room Temperature ◽  
Structural Elucidation ◽  
Side Reactions ◽  
Metal Base ◽  
Lithium Amide ◽  
Mixed Metal ◽  
Important Challenge

While fluoroaryl fragments are ubiquitous in many pharmaceuticals, the deprotonation of fluoroarenes using organolithium bases constitutes an important challenge in polar organometallic chemistry. This has been widely attributed to the low stability of the in situ generated aryl lithium intermediates that even at –78 °C can undergo unwanted side reactions. Herein, pairing lithium amide LiHMDS (HMDS = N{SiMe3}2) with FeII(HMDS)2 enables the selective deprotonation at room temperature of pentafluorobenzene and 1,3,5-trifluorobenzene via the mixed-metal base [(dioxane)LiFe(HMDS)3] (1) (dioxane = 1,4-dioxane). Structural elucidation of the organometallic intermediates [(dioxane)Li(HMDS)2Fe(ArF)] (ArF = C6F5, 2; 1,3,5-F3-C6H2, 3) prior electrophilic interception demonstrates that these deprotonations are actually ferrations, with Fe occupying the position previously filled by a hydrogen atom. Notwithstanding, the presence of lithium is essential for the reactions to take place as Fe II (HMDS)2 on its own is completely inert towards the metallation of these substrates. Interestingly 2 and 3 are thermally stable and they do not undergo benzyne formation via LiF elimination.

One-Pot Synthesis of ABC Type Triblock Copolymers via in situ Click [3 + 2] and Diels−Alder [4 + 2] Reactions

2007 ◽  
Vol 40 (2) ◽  
pp. 191-198 ◽  
Author(s):  
Hakan Durmaz ◽  
Aydan Dag ◽  
Ozcan Altintas ◽  
Tuba Erdogan ◽  
Gurkan Hizal ◽  
...  
Keyword(s):  
Triblock Copolymers ◽  
Diels Alder ◽  
One Pot ◽  
One Pot Synthesis

scholarly journals Crystal structures and conformations of two Diels–Alder adduct derivatives: 1,8-bis(thiophen-2-yl)-14-oxatetracyclo[6.5.1.02,7.09,13]tetradeca-2(7),3,5-trien-10-one and 1,8-diphenyl-14-oxatetracyclo[6.5.1.02,7.09,13] tetradeca-2,4,6-trien-10-one

2015 ◽  
Vol 71 (2) ◽  
pp. 213-216
Author(s):  
S. Gopinath ◽  
P. Narayanan ◽  
K. Sethusankar ◽  
Meganathan Nandakumar ◽  
Arasambattu K. Mohanakrishnan
Keyword(s):  
Crystal Packing ◽  
Rotation Axis ◽  
Alder Reaction ◽  
Ring System ◽  
Diels Alder ◽  
Compound I ◽  
Diels Alder Reaction ◽  
Phenyl Rings ◽  
Axis Parallel ◽  
Alder Adduct

The title compounds, C21H16O2S2(I) and C25H20O2(II), are products of a tandem `pincer' Diels–Alder reaction consisting of [2 + 2] cycloadditions between benzo[c]furan and cyclopentanone. Each comprises a fused tetracyclic ring system containing two five-membered rings (inenvelopeconformations with the O atom as the flap) and six-membered rings (inboatconformations). In addition, two thiophene rings in (I) and two phenyl rings in (II) are attached to the tetracyclic ring system. The cyclopentanone ring adopts atwistedconformation in (I) and anenvelopeconformation in (II). In (I), the thiophene rings are positionally disordered over two sets of sites, with occupancy ratios of 0.901 (2):0.099 (2) and 0.666 (2):0.334 (2). In (II), the oxygen atom of the cyclopentanone ring is rotationally disordered over two sites with an occupancy ratio of 0.579 (4):0.421 (4). The molecular structure of (I) is stabilized by an intramolecular C—H...O hydrogen bond, which generates anS(7) ring motif. In the crystal, the molecules are linkedviaweak C—H...O hydrogen bonds, which generateR22(16) ring motifs in (I) andC(8) chains in (II). In both structures, the crystal packing also features C—H...π interactions. The crystal studied of compound (I) was twinned by non-merohedry. The twin component is related by the twin law [−1 0 0 −0.101 1 −0.484 0 0 −1] operated by a twofold rotation axis parallel to thebaxis. The structure of (I) was refined with a twin scale factor of 0.275 (2).

Structural Study of an Unusual Diels-Alder Adduct

1992 ◽  
Vol 45 (12) ◽  
pp. 2089 ◽  
Author(s):  
EL Ghisalberti ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Diffraction Study ◽  
Structural Study ◽  
Spectroscopic Studies ◽  
Diels Alder ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Chemical Evidence ◽  
Alder Adduct

The structure of the compound obtained on heating the naturally occurring clerodane furanoditerpene (1) had been formulated as (2) on the basis of spectroscopic studies. A single-crystal X-ray diffraction study on the dihydro derivative of (2) has confirmed this and provides support for the stereochemistry previously assigned to (1) on the basis of chemical evidence.

scholarly journals Competitive Diels–Alder and ene addition of N-arylmaleimides to 7-dehydrocholesteryl acetate

1992 ◽  
Vol 70 (11) ◽  
pp. 2730-2744 ◽  
Author(s):  
William J. Leigh ◽  
Donald W. Hughes ◽  
D. Scott Mitchell
Keyword(s):  
Molecular Mechanics ◽  
Nmr Spectra ◽  
Benzene Solution ◽  
Diels Alder ◽  
Spectroscopic Techniques ◽  
Two Dimensional ◽  
A Minor ◽  
C Nmr ◽  
Alder Adduct ◽  
Ene Addition

Thermolysis of N-phenyl, N-para-biphenyl, and N-para, para′-terphenylmaleimide with 7-dehydrocholesteryl acetate in benzene solution at 200 °C yields mixtures of four cycloadducts in relative yields that are essentially independent of the maleimide substituent. The three major products are those of ene addition to C7 of the steroid with abstraction of the proton at C9 or C14. The α-endo-Diels-Alder adduct is formed as a minor product. The structures of the adducts have been elucidated on the basis of one- and two-dimensional 1H and 13C NMR spectroscopic techniques, including homonuclear 1H decoupling, NOE, 1H–1H COSY, heteronuclear 1H–13C shift correlation, and TOCSY 2-D experiments, and the results of molecular mechanics (MMX) calculations. The combination of these techniques has made it possible to almost completely assign the 1H and 13C NMR spectra for two of the ene adducts and the Diels–Alder adduct from reaction of 7-dehydrocholesteryl acetate with N-phenyl maleimide.

Sign in / Sign up

Export Citation Format

Share Document