Reactive Substituents Research Articles

Synthesis of liquid crystalline compounds containing thiol groups at both ends as reactive substituents and their immobilization on a gold substrate

In this study, we synthesized four bifunctional compounds containing two alkoxy groups, at which reactive thiol groups were introduced. Among these compounds, a compound with four and five methylene units in each alkyl chain did not exhibit a liquid crystalline phase. The other three compounds exhibit one or two liquid crystalline phases, and the number of liquid crystalline phases depends on the number of methylene units in their alkyl chains. These liquid crystalline compounds were oriented in one direction using a rubbed alignment film, and the oriented compounds were transferred onto a gold substrate. Using these gold substrates as working electrodes, cyclic voltammetry (CV) was performed with potassium ferricyanide as the redox probe. As the deposition time increased, the current intensities of a pair of redox waves gradually decreased. This trend suggests that with longer deposition times, a larger amount of the liquid crystalline compound was transferred to the gold substrate surface. These findings shed light on the relationship among the structures of bifunctional compounds, their liquid crystalline behavior, and their alignment properties on gold substrates, thereby offering valuable insights for potential applications in nanotechnology and materials science.

Epoxy‐functional thermoplastic copolymers and their incorporation into a thermosetting resin

AbstractThe customization of polymer networks can be made possible via dual‐functional monomers, molecules characterized by two different reactive substituents that allow for versatile methods of polymerization. The dual‐functional, epoxy‐methacrylate monomers, glycidyl methacrylate (GMA), and vanillyl alcohol epoxy‐methacrylate (VAEM), were polymerized with methyl methacrylate (MMA) via reversible addition‐fragmentation chain transfer (RAFT) polymerization to form low molecular weight (~10–20 kDa) epoxy‐functional thermoplastic copolymers, poly(VAEM‐co‐MMA), and poly(GMA‐co‐MMA). The copolymers were blended at 5 wt% into an epoxy resin system containing EPON Resin 828 and EPIKURE W Curing Agent and cured thermally to create unique interpenetrating polymer networks (IPNs). The resulting IPNs were compared to the cured neat resin and evaluated for thermal and mechanical properties, where maintained thermal properties and enhancements of stiffness and toughness were demonstrated.

Hydrogenation of Substituted Benzenes Containing Nitro and Azo Groups over Skeletal Nickel in Aqueous Solutions of 2-Propanol

An analysis is made of the kinetic characteristics of the hydrogenation of 4-nitro- and 2-nitro-2'-hydroxy-5'-methylazobenzenes, 4-nitroaniline and 4-aminoazobenzene over skeletal nickel in neutral azeotropic 2-propanol–water mixture and in the same solvent in the presence of acetic acid or sodium hydroxide. It is found that the selectivity of the hydrogenation of these isomers to the intermediate products depends on the composition and nature of the solvent, and is determined by the rate of reactive group conversion. Compared to the process in the presence of sodium hydroxide, which suppresses the route leading to the predominant hydrogenation of the nitro group, the contribution from the transformation of azo group is considerably greater in the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene in the presence of acetic acid. Adding a base to the solvent during the hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene accelerates the rate of nitro group conversion and the intramolecular cyclization of the intermediate compound, increasing the selectivity towards the products containing the benzotriazole cycle (particularly 2-(2-hydroxy-5-methylphenyl)benzotriazole-N-oxide). The almost linear correlation between the selectivity of the catalytic hydrogenation of isomers of nitro-2'-hydroxy-5'-methylazobenzene and the kinetic characteristics of the hydrogenation of nitro and azo groups in compounds containing a single reactive substituent at different values of medium’s pH is estimated.

P‐83: Comparison of Characteristic Pattern Form along the Photo‐resist Binders

Deep color technology enables more vivid colors to be realized on the display. The fabrication of deep color filters requires a high degree of patterning technology. The binder of the photoresist has an important role in formation of color filter patterns. The pattern characteristics are affected by the binder contents (%) and type of binders whether they have reactive substituents or not and what their molecular weight is.

Copolymers of ethylene with monoalkenyl- and monoalkenyl(siloxy)silsesquioxane (POSS) comonomers – Synthesis and characterization

The hybrid ethylene/POSS copolymers were obtained using the rac-Et(Ind)2ZrCl2 catalyst activated by MAO. A series of monoalkenyl- and monoalkenyl(siloxy)silsesquioxanes derivatives with different structures of reactive alkenyl substituent and types of non-reactive groups attached to the T8 POSS cage was used as comonomers. The kind and concentration of the POSS comonomer in the reaction feed as well as extended reaction time were found to strongly influence the catalyst efficiency and incorporation of POSS units into polymer chains. The comonomer reactivity was significantly dependent on the length of the alkenyl reactive substituent in the POSS molecule and it was highest for the POSS structures with medium-length of the alkenyl substituent due to their steric and inductive effects of the silicon-oxygen cage. The molecular weight as well as the kind and the content of unsaturated end groups in copolymers were dependent on the kind and amount of POSS comonomer in the reaction feed. The change in melting temperature, crystallinity degree, crystallization temperature and morphology of copolymers was observed as compared to neat polyethylene (PE).

Targeted attachment of functional groups at Ge9 clusters via silylation reactions.

Molecules with low-valent Ge atoms are generally synthesized from organohalogen germanes as precursors. The Zintl phase K4Ge9 provides reactive building blocks for a targeted synthesis of germanium-rich molecules. The silylation of Ge9 clusters with chlorosilanes ClSiR2R', that carry unsaturated olefin groups R' leads to the introduction of olefinic side chains of variable lengths allowing for further reactions. The compounds K[Ge9{Si(SiMe3)3}2(SiPh2R')] (R' = -CH[double bond, length as m-dash]CH2 (1); -(CH2)3CH[double bond, length as m-dash]CH2 (2)) carry one such functionality, whereas K[Ge9(SiPh2R')3] (3 and 4) offer the possibility for an interconnection of clusters due to three functional groups on the Ge9 core. XPS measurements show that the silylated clusters are much more air-stable than the unsubstituted, bare cluster units.

Adenovirus vector-based incorporation of a photo-cross-linkable amino acid into proteins in human primary cells and cancerous cell lines.

The site-specific incorporation of cross-linkable designer amino acids into proteins is useful for covalently bonding protein complexes upon exposure to light. This technology can be used to study networks of protein-protein interactions in living cells; however, to date it has only been applicable for use with a narrow range of cell types, due to the limited availability of plasmid-based transfection protocols. In the present study, we achieved adenovirus-based expression of a variant of an archaeal pyrrolysyl-tRNA synthetase and UAG-recognising tRNA pair, which was used to incorporate unnatural amino acids into proteins at sites defined by in-frame UAG codons within genes. As such, the site-specific photo-cross-linking method is now applicable to a wide variety of mammalian cells. In addition, we repositioned the reactive substituent of a useful photo-cross-linker, Nε-(para-trifluoromethyl-diazirinyl-benzyloxycarbonyl)-l-lysine (pTmdZLys), to the meta position, which improved its availability at low concentration. Finally, we successfully applied this system to analyse the formation of a protein complex in response to a growth signal in human cancerous cells and human umbilical vein endothelial cells. This adenovirus-based system, together with the newly designed cross-linkable amino acid, will facilitate studies on molecular interactions in various cell lines of medical interest.

ChemInform Abstract: Solvent‐Free Multicomponent Synthesis of Biologically‐Active Fused‐Imidazo Heterocycles Catalyzed by Reusable Yb(OTf)3 Under Microwave Irradiation.

A rapid, efficient and solvent-free – green – protocol for Groebke–Bienayme–Blackburn reaction (G−B-B reaction) for the synthesis of fused-imidazo heterocycles has been developed. The methodology reported here involves multi-component reaction (MCR) catalyzed by reusable Yb(OTf)3 (a mild and water-compatible Lewis acid) under microwave irradiation which allows fast and efficient preparation of the title compounds in excellent yield. The salient features of our protocol are solvent-free, low catalyst loading (2.5–0.1 mol%) with good turnover number (TON: 890) and turnover frequency (TOF: 178/min), less reaction time (5 min), no dependency over specialized purification (by either column chromatography or recrystallization) and very high isolated yield (95–99 %) with excellent green chemistry metrics (E-factor: 0.071 and Mass Intensity: 1.071). The water compatibility of the catalyst Yb(OTf)3 has been exploited for its efficient recovery through water washings. In addition, the other exciting milestones of the protocol are catalyst and workup solvent recycling, excellent conversion with notorious substrates such as enolizable aldehyde or isonitrile bearing reactive substituent, very efficient at higher scale (50 mmol) and easy to couple with other methods (one-pot two-step cyclization: G−B-B reaction and Ullmann-type coupling).

Towards Iron-Catalyzed Sonogashira Cross-Coupling Reactions

Herein we report on the selective iron-catalyzed cross-coupling reaction of terminal phenylacetylenes with iodo-aryl derivatives to afford the respective coupling products in the presence of 10 mol% FeCl2(bdmd) and 10 mol% [Cu(CH3CN)4]BF4 (bdmd=bis((diphenylphosphanyl)methyl)diphenylsilane). The yields are moderate to good in 1,4-dioxane or DMF. This is the first example of a well-defined and fully analysed ferrous complex acting as a precatalyst in Sonogashira cross-coupling reactions. Notably, FeCl2(bdmd) is compatible with reactive substituents such as carbonyl-, carboxyl-, hydroxy-, and amino-groups, which allows for an effective cross-coupling reaction in the presence of such functional groups.

Thermal curing and degradation behaviour of silicon-containing arylacetylene resins

Silicon-containing aryacetylene resins (PSAs) have already shown potential application as heat-resistant materials due to their excellent thermal stability. The formation and degradation of structures in cured PSAs are very important to evaluate the thermal properties during their applications. Herein, the thermal curing and degradation behavior of PSAs with different substituents were investigated by DSC, FT-IR, Py-GC-MS, TGA and TG-GC-MS. DSC and FT-IR analysis reveals that the curing reaction is dominated by the crosslinking reaction of CCH and SiCC, meanwhile, the reactive substituents (such as SiH and SiCHCH2) could promote the CCH and SiCC reaction with higher conversion. Py-GC-MS was used to detect the pyrolysis products at 650 °C and 750 °C, respectively, and the results could provide important information about the curing reaction and structures of cured PSAs. The curing reaction of PSAs mainly contains cyclotrimerization and Diels-Alder reaction of CCH and SiCC, and some addition reaction to form polyene structure. The main structures in cured PSAs contain a lot of phenyl rings, some aromatic fused rings and a little of polyene structure, moreover, their contents in cured PSAs are dependent on the substituents of the precursors. The TGA results show that the substituents of SiH and SiCHCH2 can effectively improve the crosslinking index of the cured PSA-H and PSA-V, and endow them with better thermal stability. Additionally, the degradation behavior of cured PSAs have been well studied by TG-GC-MS. When the temperature is 400 °C, the SiCH3 and some aliphatic structure begin to degrade and form CH4, and with the temperature increasing to 500 °C, the unsaturated and aliphatic structures decompose into C2H4 and C2H6, and after 600 °C, the aromatic rings and fused rings in cured PSAs are dehydrogenated and release H2. In addition, the content of the degradation products and their forming temperature are also related with the substituents.

Solvent–free Multicomponent Synthesis of Biologically–active Fused–imidazo Heterocycles Catalyzed by Reusable Yb(OTf)3 Under Microwave Irradiation

AbstractA rapid, efficient and solvent‐free – green – protocol for Groebke–Bienaymé–Blackburn reaction (G−B‐B reaction) for the synthesis of fused‐imidazo heterocycles has been developed. The methodology reported here involves multi‐component reaction (MCR) catalyzed by reusable Yb(OTf)3 (a mild and water‐compatible Lewis acid) under microwave irradiation which allows fast and efficient preparation of the title compounds in excellent yield. The salient features of our protocol are solvent‐free, low catalyst loading (2.5–0.1 mol%) with good turnover number (TON: 890) and turnover frequency (TOF: 178/min), less reaction time (5 min), no dependency over specialized purification (by either column chromatography or recrystallization) and very high isolated yield (95–99 %) with excellent green chemistry metrics (E‐factor: 0.071 and Mass Intensity: 1.071). The water compatibility of the catalyst Yb(OTf)3 has been exploited for its efficient recovery through water washings. In addition, the other exciting milestones of the protocol are catalyst and workup solvent recycling, excellent conversion with notorious substrates such as enolizable aldehyde or isonitrile bearing reactive substituent, very efficient at higher scale (50 mmol) and easy to couple with other methods (one‐pot two‐step cyclization: G−B‐B reaction and Ullmann‐type coupling).

Unusual exchange of substituents in reactions of alkylene oxides with organic compounds containing β-hydroxyalkyl groups at S, Se, N, and P heteroatoms

The mechanism of an unusual exchange of substituents in a previously unknown reaction of alkylene oxides with organic compounds containing β-hydroxyalkyl groups at the S, Se, N, and P heteroatoms is examined. Such exchange reactions are demonstrated to occur in many systems. The reactions of alkylene oxide with β-hydroxyalkyl sulfides are studied quantitatively.

Intracranial Glioblastomas: New Hope for an Effective Treatment

Intracranial Glioblastomas: New Hope for an Effective Treatment

Stepwise conversion of flavonoids by engineered dioxygenases and dehydrogenase: Characterization of novel biotransformation products

Flavonoids are a large group of plant secondary metabolites that exert various biological and pharmacological effects. In this context, the generation of derivatives is of considerable interest. The introduction of hydroxy groups is of particular relevance, as they are known to be involved in many of the biological interactions and furthermore enable additional modifications, such as glycosylations. Bacterial aryl-hydroxylating dioxygenases (ARHDOs) have proven to be very useful for the conversion of aromatic structures into versatile building blocks for different kinds of derivatizations. Such enzymes have been used with varying success for the oxidation of flavonoids. In order to find better ARHDOs for the hydroxylation of such substrates, we carried out biotransformation trials with a collection of hybrid ARHDOs of different origin, using resting cells of recombinant strains. This identified enzymes able to transform all of the flavonoids examined, typically in yields above 50%. It also showed that moderately reactive substituents of flavonoids, such as hydroxy or amino groups, can lead to spontaneous follow-up reactions with the dienediol structures generated by dioxygenation. A report of flavanone epoxidation, a reaction never before observed to be catalyzed by an ARHDO, is challenged by our results. All ARHDOs examined converted this substrate into a dehydrogenase-transformable dihydrodiol. All dihydrodiols obtained by dioxygenation of the examined flavonoids were successfully re-aromatized into catechols by a bacterial dehydrogenase. These metabolites were usually stable. However, the catechols formed from flavanone and 2’-hydroxy-chalcone, respectively, were interconvertible under mild conditions. Altogether, we isolated and characterized 13 compounds that have not previously been described. The biotransformations reported here give access to novel flavonoid derivatives that may be applied for biological screens as well as for further modification, such as glycodiversification.

Csp3-csp3 homocoupling reaction of benzyl halides catalyzed by rhodium.

A highly reactive alkylrhodium complex was formed from Me(2)Zn and RhCl(PPh(3))(3) and effectively catalyzed a Csp(3)-Csp(3) homocoupling reaction of benzyl halides. A Csp(3)-Csp(3) coupling reaction using Rh catalyst has not been reported up to now. The reaction proceeded under very mild conditions and gave the corresponding homocoupling products even if they had reactive substituents such as an uncovered formyl or hydroxymethyl group.

Metal‐Free Oxidative Coupling: Xanthone Formation via Direct Annulation of 2‐Aryloxybenzaldehyde using Tetrabutylammonium Bromide as a Promoter in Aqueous Medium

AbstractA metal‐free intramolecular annulation of 2‐aryloxybenzaldehydes to xanthones is disclosed, which proceeds through the direct oxidative coupling of an aldehyde CH bond and aromatic CH bonds using tetrabutylammonium bromide (TBAB) as a promoter in aqueous medium. This strategy works smoothly in the presence of both electron‐donating and electron‐withdrawing groups, and displays good tolerance towards catalytically reactive substituents, thus promising further functionalizations of xanthone products.magnified image

ChemInform Abstract: An Efficient Synthesis of (Z)‐α‐Fluorochalcones via the Palladium‐Catalyzed Cross‐Coupling Reaction of (Z)‐α‐Fluorocinnamoyl Chloride with Boronic Acids.

AbstractThis method is useful for the preparation of naturally occurring chalcones and it opens the route to a general synthesis of (Z)‐α‐fluoro‐α,β‐unsaturated ketones bearing reactive substituents.

Synthesis of new silica gel adsorbent anchored with macrocyclic receptors for specific recognition of cesium cation

In this article, a new class of silica gel adsorbent functionalized with macrocyclic receptors was developed for cesium recognition. A calixcrown molecule, with strong affinity to cesium cation, was decorated precisely at the 1,3-alternate benzene rings with reactive amino substituents, followed by the anchoring to the silica matrix to obtain a high functionalization degree. Structural characterization of the monomers and the organosilicas was carried out by 1H/13C NMR, 29Si/13C solid-state NMR, and FT-IR spectra. Besides, XPS survey, BET, TGA and ESEM were employed to investigate the surface property, thermal stability and micro-morphology of the organosilicas. Due to the host–guest interaction between the calixcrown receptor and cesium cation, efficient separation of cesium in the presence of competing alkali metals including sodium and potassium was realized. Mechanism regarding the recognition effect was discussed. The calixcrown-grafted organosilica material possesses the potential to be applied for the separation of cesium in radioactive liquid waste.

Orthoamides and Iminium Salts LXXXII: Cleavage of Orthoamides of Alkynecarboxylic Acids by Elemental Iodine – A New Method for the Preparation of Vinylogous Guanidinium Salts

Orthoamides of six alkynecarboxylic acids, possessing reactive substituents in 3-position, are transformed by elemental iodine to the corresponding vinylogous guanidinium iodides. The constitution of two of the iodides was established by crystal-structure­ analysis.

ChemInform Abstract: Rearrangement of 2‐Aryloxybenzaldehydes to 2‐Hydroxybenzophenones by Rhodium‐Catalyzed Cleavage of Aryloxy C—O Bonds.

AbstractThe title reaction tolerates the presence of various reactive substituents such as aryl halides, nitrile, and esters.