Functionalization of Calix[4]resorcinolarenes with Trimethylsilyl Isocyanate

Calix[4]resorcinolarenes and their dialkylaminomethylated derivatives react with trimethylsilyl isocyanate to form addition products containing four silylcarbamate groups. These compounds are unstable and, depending on the nature of alkyl groups at the lower rim of the macrocycle, undergo two types of transformations. Intramolecular silylation yields calixarenes containing four carbamate and four trimethylsilyloxy groups at the upper rim. In the case of dialkylaminomethylated calixarenes, the initially formed addition products can undergo intramolecular cyclization to form a cavitand with four six-membered fragments at the upper rim.     

Does Urea Preferentially Interact with Amide Moieties or Nonpolar Sidechains? A Question Answered Through a Judicious Selection of Model Systems

The transfer model suggests that urea unfolds proteins mainly by increasing the solubility of the amide backbone, probably through urea-induced increase in hydrogen bonding. Other studies suggest that urea addition increases the magnitude of solvent-solute van der Waals interactions, which increases the solubility of nonpolar sidechains. More recent analyses hypothesize that urea has a similar effect in increasing the solubility of backbone and sidechain groups. In this work, we compare the effects of urea addition on the solvation of amides and alkyl groups. At first, we study the effects of urea addition upon solvent hydrogen bonding acidity and basicity through the perturbation in the fluorescence spectrum of probes 1-AN and 1-DMAN. Our results demonstrate that the solvent's hydrogen bonding properties are minimally affected by urea addition. Subsequently, we show that urea addition does not perturb the intra-molecular hydrogen bonding in salicylic acid significantly. Finally, we investigate how urea preferentially interacts with amide and alkyl groups moieties in water by comparing the effects of urea addition upon the solubility of acetaminophen and 4-tertbutylphenol. We show that urea affects amide and t-butyl solubility (lowers the transfer free energy of both amide (backbone) and alkyl (sidechain) groups) in a similar fashion. In other words, preferential interaction of urea with both moieties contributes to protein denaturation.     

Direct Nucleophilic Addition to N‐Alkoxyamides

While the synthesis of amide bonds is now one of the most reliable organic reactions, functionalization of amide carbonyl groups has been a long‐standing issue due to their high stability. As an ongoing program aimed at practical transformation of amides, we developed a direct nucleophilic addition to N‐alkoxyamides to access multisubstituted amines. The reaction enabled installation of two different functional groups to amide carbonyl groups in one pot. The N‐alkoxy group played important roles in this reaction. First, it removed the requirement for an extra preactivation step prior to nucleophilic addition to activate inert amide carbonyl groups. Second, the N‐alkoxy group formed a five‐membered chelated complex after the first nucleophilic addition, resulting in suppression of an extra addition of the first nucleophile. While diisobutylaluminum hydride (DIBAL‐H) and organolithium reagents were suitable as the first nucleophile, allylation, cyanation, and vinylation were possible in the second addition including inter‐ and intramolecular reactions. The yields were generally high, even in the synthesis of sterically hindered α‐trisubstituted amines. The reaction exhibited wide substrate scope, including acyclic amides, five‐ and six‐membered lactams, and macrolactams.     

A convenient AIBN-initiated radical addition of ethyl iododifluoroacetate to alkenes

The AIBN-initiated addition of ethyl 4-iodo-2,2-difluoroacetate to a variety of alkene substrates is described. The addition generally led to the corresponding addition products in good to excellent yields and various functional groups could be tolerated under the reaction conditions.     

Synthesis of photopolymers with pendant cyclic carbonate and cinnamic ester groups

Photopolymers with both pendant cyclic carbonate groups and cinnamic ester groups were synthesized by the addition reaction of poly(glycidyl methacryalte-co-styrene)[poly(GMA-co-AN)] with carbon dioxide and then with cinnamoyl chloride. Soluble quaternary ammonium salt catalysts showed good yield of cinnamoyl chloride addition to the glycidyl methacrylate groups. Quaternary salt catalysts of longer alkyl chain length and of more nucleophilic anion offered higher yield of cinnamoyl chloride addition. Photochemical reaction test showed that poly(CNMA-co-DOMA-co-St) had a good photosensitivity. This revised version was published online in June 2006 with corrections to the Cover Date.     

双氰胺固化环氧树脂的研究

<正> 双氰胺做为环氧树脂的固化剂,其贮存期可以达到一年以上,这种固化物的机械和介电性能优异,因此,广泛用于制造层压等电工材料方面。国外许多人都曾对双氰胺与环氧树脂的固化反应历程和固化物的性能做过研究,指出了在固化过程中化学结构的变化     

Utilization of oxygen difluoride for syntheses of fluoropolymers

The utilization of OF₂, for chain extension of polyperfluoropolyenes, insertion of functional groups into the polymer structure and addition copolymerization with perfluorodiene is described. The results of reactions of OF₂ and polyperfluoro-1,2- and -1,4-butadiene indicate that conditions can be selected either to extend the polymer chain or to insert acyl fluoride groups into the polymer structure. Ambient and higher temperatures favor insertion of acyl fluoride groups. At 0°C chain extension occurs without introduction of acyl fluoride groups. Preliminary results on the novel synthesis of perfluoroalkylene oxide polymer by addition copolymerization of perfluorobutadiene and OF₂ is also reported.     

Cyanoesterification of 1,2-dienes: synthesis and transformations of highly functionalized alpha-cyanomethylacrylate esters

A Ni/PMe2Ph catalyst is found to effect regioselective addition of cyanoformate esters across 1,2-dienes, giving rise to 3-alkoxycarbonyl-3-butenenitriles. Functional groups such as cyano, protected hydroxyl, and amino groups in the 1,2-diene substrates are tolerated. Isomerization of the initial products to thermodynamically more stable isomers takes place possibly through further oxidative addition of the C-CN bond of 3-alkoxycarbonyl-3-butenenitriles to Ni(0) followed by reductive elimination. The cyanoesterification products undergo further addition across alkynes in the presence of a Ni/P(4-CF3-C6H4)3 catalyst.     

Substituted propenyl end groups as reactive intermediates in radical polymerization

The addition of propagating radicals of methyl acrylate (MA) and styrene (St) to CH₂?C(CO₂CH₃)CH₂? and CH₂?C(C₆H₅)CH₂? ω‐end groups of poly(methyl methacrylate) (PMMA) and polystyrene (PSt) was investigated. The end groups were as reactive as MA and St toward the poly(methyl acrylate) (PMA) and PSt radicals, respectively. The adduct radical derived from the two types of PMMA end groups and PMA radicals underwent β fragmentation exclusively to yield PMMA radicals and end groups bound to PMA chains. The addition of PSt radicals to PMMA with CH₂?C(CO₂Me)CH₂? end groups resulted in adduct radicals that underwent β fragmentation and addition to St or coupling with PSt radicals. Adduct radicals formed by the addition of PMA radicals to both types of end groups of PSt exclusively formed C? C bond by coupling with PMA radicals to form branched structures or by addition to MA monomer to give a copolymer. The fate of the adduct radicals was highly dependent on the type of polymer chain and the substituent bound to the end group. Steric congestion of the adduct radical arising from the α‐methyl group of the PMMA chain was considered to be crucial for fragmentation to expel the PMMA radical. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 645–654, 2003     

Post-polymerization functionalization of linear polyglycidol with diethyl vinylphosphonate

In this communication we report on the base catalyzed Michael addition of the hydroxy methyl side groups in polyglycidol to diethyl vinyl phosphonate. Hydrolysis of the diethyl phosphonato ethyl side groups with bromotrimethylsilane leads to a new class of polyglycidols with pendant phosphonic acid groups.     

Building carbohydrates on the dioxanone scaffold: stereoselective synthesis of d-glycero-d-manno-2-octulose

The title compound has been synthesized via two proline-catalyzed aldol addition reactions of 2,2-dialkyl-1,3-dioxan-5-ones: the first addition to 1,3-dithiane-2-carboxaldehyde, followed by reduction to the corresponding diol, protection of the OH groups and dithiane hydrolysis afforded a protected d-ribose that was used in the second aldol addition reaction.     

New Prospects for the Grafting of Functional Groups onto Aliphatic Polyesters. Ring-Opening Polymerization of α- or γ-Substituted ε-Caprolactone Followed by Chemical Derivatization of the Substituents

Recent progress in the synthesis of aliphatic polyesters, substituted by pendent functional groups, has been reviewed. Two main strategies have to be distinguished. The first route consists of the ring-opening polymerization of ε-caprolactone substituted by various functional groups, protected if needed, in α- or γ-position. In a second strategy, the functional groups are grafted onto preformed polyesters chains in α-position of the carbonyl groups. α-chloro-ε-caprolactone is quite an interesting monomer because, after polymerization, the activated chloride can be easily derivatized by atom transfer radical addition and “click” chemistry, respectively. Similarly, γ-acrylic-ε-caprolactone is precursor of (co)polyesters well-suited to derivatization of the pendent double bonds by Michael addition.     

Synthesis of core-shell structured polymers with inserted thioether from a multi-functional scaffold

The synthesis of a thioether inserted, core-shell structured polymer from the scaffold of hyperbranched polyglycerol (PG) was described. PG was first allyl functionalized, and in the presence of AIBN, the allyl groups further underwent radical addition to thiol compounds, thus thiol functional polyethylene oxide monomether (MPEO) were grafted onto PG. Similarly, 2-mercaptoethy-lammonium chloride was introduced onto PG via thiol addition, and the residual amino groups were further quaternized with decyl bromide, leading to an amphiphilic core-shell structure polymer.     

Polycarbonate-modified epoxies. I. Studies on the reactions of epoxy resin/polycarbonate blends prior to cure

An epoxy resin based upon the diglycidyl ether of bisphenol-A was modified with poly(bisphenol A carbonate) (PC). Prior to aromatic amine cure, the possible reactions in the epoxy resin/PC blend were investigated using GPC and FTIR techniques. It was shown that at 150°C, the epoxy resin acted as a plasticizer and promoted the crystallization of PC. In addition, a transesterification between the secondary hydroxyl groups in the epoxy resin with the carbonate groups in PC occurred. This reaction resulted in degraded PC chains with phenolic hydroxyl end groups. There was no evidence of reaction of epoxide groups at 150°C in this blend. At 200°C, the secondary hydroxyl groups acted as a catalyst converting most of the aromatic–aromatic carbonates to the aromaticndash;liphatic and aliphaticndash;aliphatic carbonates through transesterification. At this elevated temperature, the secondary hydroxyl groups were regenerated by the addition reaction between the epoxide groups and the phenolic hydroxyl end groups, either from the transesterification or the hydrolysis of PC. This addition reaction combining the PC chains and epoxy chains eventually resulted in a crosslinked polymer if the extent of reaction was high. Thus, by using a melt blending process at high temperature, e.g., 200°C, a copolymer network structure of PC-modified epoxy could be formed. The fracture toughness should be increased by increasing the capability for plastic deformation due to the incorporation of PC chains into the network; results will be reported in a future study. © 1996 John Wiley & Sons, Inc.     

Nanometric morphological variation of zinc oxide crystals using organic molecules with carboxy and sulfonic groups

The morphological variation of wurtzite-type zinc oxide (ZnO) grown on a substrate in basic aqueous solutions was investigated using a wide variety of organic molecules with carboxy and sulfonic groups. The effect of the organic molecules on the nanometric morphology was classified into several categories. Hexagonal plates exhibiting the (001) planes were obtained by a planarizing effect with the addition of citric, tartaric, and maleic acids, although acetic, salicylic, fumaric, and succinic acids exhibited no effects on the morphology. The production of nanograins was observed by a miniaturizing effect with the addition of a polymeric molecule with carboxy groups and an anionic surfactant with a sulfonic group. Mosaic structures composed of granular crystals and bundles consisting of fibrils elongated in a direction toward the c-axis were produced by the addition of bulky dye molecules having benzene rings and carboxy or sulfonic groups. The influence of the organic molecules was related to the number of the functional groups and the stereochemical structure. The findings of this study suggest that the adsorbability of the organic molecules depending on the chemical structure to the specific crystal faces is essential for the variation of the nanometric morphology.     

Intermolecular reductive radical addition to 2-(2,2,2-trifluoroethylidene)-1,3-dithiane 1-oxide: experimental and theoretical studies

Tin hydride mediated radical addition of organic halide to 2-(2,2,2-trifluoroethylidene)-1,3-dithiane 1-oxide has been devised. The reaction is equivalent to an unrealizable radical addition to trifluoromethylketene, providing useful α-trifluoromethyl carbonyl equivalents. The trifluoromethyl and the sulfoxide groups of the substrate play key roles for the success of the radical addition, lowering the barrier of the radical addition step and controlling the stereoselectivity of the reaction, which DFT calculations have elucidated.     

Regiochemistry of [70]fullerene: preparation of C70(OOtBu)n (n = 2, 4, 6, 8, 10) through both equatorial and cyclopentadienyl addition modes

[reaction: see text] tert-Butylperoxy radicals add to [70]fullerene to form a mixture of adducts C(70)(OO(t)()Bu)(n)() (n = 2, 4, 6, 8, 10). Four isomers were isolated for the bis-adduct with the two tert-butylperoxo groups attached at 1,2-, 5,6-, 7,23-, and 2,5-positions, respectively. Two isomers were isolated for the tetrakis-adduct with the tert-butylperoxo groups located along the equator in C(s)() symmetry and on the side in C(1) symmetry, respectively. Similarly, two isomers were isolated for the hexakis-adducts with a structure related to the tetrakis-adducts, one of which has the cyclopentadienyl substructure. No isomer was detected for the octakis- and decakis-adducts. The C(s)()-symmetric octakis- and C(2)-symmetric decakis-adducts have all the tert-butylperoxo groups located along the equator. The decakis-adduct is the major product under optimized conditions. The compounds were characterized by their spectroscopic data. Chemical correlation through further addition of tert-butylperoxy radicals to isolated pure derivatives confirmed the structure assignment. Mechanisms of the tert-butylperoxy radical addition to C(70) follow two pathways: equatorial addition along the belt and cyclopentadienyl addition on the side.     

2,3-Unsaturated enoses. A Pummerer rearrangement route to sugar vinyl sulfides and synthesis of 3-deoxy-3-alkyl/arylsulfinyl pyranosides

A Pummerer rearrangement of 2,3-dideoxy-3-alkyl/arylsulfinyl-arabino-hexopyranosides is reported. Treatment of sulfinyl-arabino-hexopyranoside derivatives, obtained through oxidation of the corresponding thio-derivatives, with trifluoroacetic anhydride (TFAA)/pyridine led to a facile formation of 2,3-dideoxy-3-alkyl/arylthio-hex-2-enopyranosides. Upon conversion of sugar vinyl sulfides to vinyl sulfoxides, conjugate addition reactions were conducted with alkoxides, to afford 3-deoxy-3-alkyl/arylsulfinyl pyranosides, in the manno-configuration exclusively. Whereas the conjugate addition reaction did not proceed with ether protecting groups, ester protecting groups and free hydroxyl groups in the sugar vinyl sulfoxide permitted the reaction.     

超支化聚负离子/超支化聚正离子自组装膜的制备及反应

自1991年以来,静电吸附自组装已发展成为制备具有特定纳米微结构聚电介质多层超薄膜的有效技术。近年来,由于树枝状聚合物和超支化聚合物独特的物理化学性质,文献中已将它们与线性聚电解质一起用于静电吸附自组装过程,但完全基于超支化聚合物分子间的自组装过程还鲜见报道,超支化聚合物所具有的大量末端和内部（如叔胺基）官能团,不仅可以用于调节自组装行为及组装膜的表面形貌,     

Scale-up synthesis of vinyl polymer-grafted nano-sized silica by radical polymerization of vinyl monomers initiated by surface initiating groups in the solvent-free dry-system

For the purpose of the prevention of the environmental pollution and the simplification of reaction process, the scale-up radical graft polymerization of vinyl monomers onto nano-sized silica surface initiated by azo groups and peroxycarbonate groups previously introduced onto the surface in the solvent-free dry-system was investigated. The introduction of azo groups onto the silica surface was achieved by the reaction of surface amino groups with 4,4′-azobis(4-cyanopentanoic acid chloride). On the other hand, the introduction of peroxycarbonate groups onto the silica surface was achieved by Michael addition of surface amino groups to t-butylperoxy-2-methacryloyloxyethylcarbonate. The graft polymerization of vinyl monomers onto the surface was successfully achieved by splaying monomers to nano-sized silica having azo and peroxycarbonate groups in solvent-free dry-system. It is interesting to note that the formation of ungrafted polymer was depressed in comparison with graft polymerization in solution: the grafting efficiency was 90-95%. In addition, in the solvent-free dry-system, the grafting of copolymer having pendant peroxycarbonate groups onto the nano-sized silica surface and the radical postgraft polymerization of styrene initiated by the pendant initiating groups of the grafted copolymer chain on the silica surface was investigated.