共查询到20条相似文献,搜索用时 15 毫秒
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Dr. Richard J. Burford Dr. Bo Li Dr. Monica Vasiliu Prof. Dr. David A. Dixon Prof. Dr. Shih‐Yuan Liu 《Angewandte Chemie (International ed. in English)》2015,54(27):7823-7827
Diels–Alder reactions employing 1,2‐azaborine heterocycles as 1,3‐dienes are reported. Carbocyclic compounds with high stereochemical and functional complexity are produced, as exemplified by the straightforward two‐step synthesis of an amino allyl boronic ester bearing four contiguous stereocenters as a single diastereomer. Whereas electron‐deficient dienophiles undergo irreversible Diels–Alder reactions, a reversible Diels–Alder reaction with the less electron‐deficient methyl acrylate is observed. Both the N and the B substituent of the 1,2‐azaborine exert significant influence on the [4+2] cycloaddition reactivity as well as the aromatic character of the heterocycle. The experimentally determined thermodynamic parameters of the reversible Diels–Alder reaction between 1,2‐azaborines and methyl acrylate correlate with aromaticity trends and place 1,2‐azaborines approximately between furan and thiophene on the aromaticity scale. 相似文献
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Guido Sello 《Journal of Molecular Structure》1995,340(1-3):15-28
A novel empirical method of calculating atomic charges in 3D structures is presented as an extension of our previous topological approach. It is based on the use of atomic electronegativity and covalent radius in order to control the electronic distribution of the molecule. Some examples are discussed in detail and the results compared with those obtained by quantum mechanical approaches. Merits and inadequacies are described, focusing on the sensitivity of the method to the distribution of atoms in 3D space and on its capability of calculating feasible charges. 相似文献
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Tugba Dispinar Rana Sanyal Amitav Sanyal 《Journal of polymer science. Part A, Polymer chemistry》2007,45(20):4545-4551
Polymers containing thiol‐reactive maleimide groups on their side chains have been synthesized by utilization of a novel methacrylate monomer containing a masked maleimide. Diels‐Alder reaction between furan and maleimide was adapted for the protection of the reactive maleimide double bond prior to polymerization. AIBN initiated free radical polymerization was utilized for synthesis of copolymers containing masked maleimide groups. No unmasking of the maleimide group was evident under the polymerization conditions. The maleimide groups in the side chain of the polymers were unmasked into their reactive form by utilization of retro Diels‐Alder reaction. This cycloreversion was monitored by thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), and 1H and 13C NMR spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4545–4551, 2007 相似文献
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Ozgul Gok Hakan Durmaz Emrah Soner Ozdes Gurkan Hizal Umit Tunca Amitav Sanyal 《Journal of polymer science. Part A, Polymer chemistry》2010,48(12):2546-2556
Multiarm star polymers containing thiol‐reactive maleimide groups at their core have been synthesized by utilization of atom transfer radical polymerization (ATRP) of various methacrylates using a masked maleimide containing multiarm initiator. One end of the initiator contains multiple halogen groups that produce the star architecture upon polymerization and the other end contains a masked maleimide functional group. Unmasking of the maleimide group after the polymerization provides the thiol reactive maleimide core that is widely used in bioconjugation. Functionalization of the core maleimide group with a thiol containing tripeptide was used to demonstrate facile reactivity of the core of these multiarm polymers under reagent‐free conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2546–2556, 2010 相似文献