Search results for "Addition reaction"
showing 10 items of 125 documents
Kondrat'eva ligation: Diels-Alder-based irreversible reaction for bioconjugation.
2014
International audience; Diversification of existing chemoselective ligations is required to efficiently access complex and well-defined biomolecular assemblies with unique and valuable properties. The development and bioconjugation applications of a novel Diels-Alder-based irreversible site-specific ligation are reported. The strategy is based on a Kondrat'eva cycloaddition between bioinert and readily functionalizable 5-alkoxyoxazoles and maleimides that readily react together under mild and easily tunable reaction conditions to afford a fully stable pyridine scaffold. The potential of this novel bioconjugation is demonstrated through the preparation of fluorescent conjugates of biomolecul…
Modular Assembly of Multimodal Imaging Agents through an Inverse Electron Demand Diels–Alder Reaction
2019
International audience; The combination of two imaging probes on a same biomolecule gives access to targeted bimodal imaging agents that can provide more accurate diagnosis, complementary information, or that may be used in different applications, such as PET imaging and fluorescence imagingassisted surgery. In this study, we demonstrate that dichlorotetrazine, a small, commercially available compound, can be used as a modular platform to easily assemble various imaging probes. Doubly-labeled tetrazines can then be conjugated to a protein through a biorthogonal IEDDA reaction. A series of difunctionalized tetrazine compounds containing various chelating agents and fluorescent dyes was synth…
Unveiling the Different Reactivity of Bent and Linear Three-Atom-Components Participating in [3 + 2] Cycloaddition Reactions
2021
The reactivity of a series of pairs of bent and linear three-atom-component (B-TACs and L-TACs) participating in [3 + 2] cycloaddition (32CA) reactions towards ethylene and electrophilic dicyanoethylene (DCE) have been studied within the Molecular Electron Density Theory. While the pseudodiradical structure of B-TACs changes to that of pseudoradical or carbenoid L-TACs upon dehydrogenation, zwitterionic B-TACs remain unchanged. Conceptual Density Functional Theory (CDFT) indices characterize five of the nine TACs as strong nucleophiles participating in polar reactions towards electrophilic ethylenes. The activation energies of the 32CA reactions with electrophilic DCE range from 0.5 to 22.0…
Design, Construction, and Characterization of a New Regioisomer and Diastereomer Material Based on the Spirooxindole Scaffold Incorporating a Sulphon…
2020
The 1,3-dipolar cycloaddition reaction is one of the most rapid, and efficient protocols to access, and construct highly divergent heterocycle chiral auxiliaries. Free catalyst synthesis of spirooxindole scaffold incorporating sulphone moiety via one pot&ndash
ChemInform Abstract: Dihydrooxazine Oxides as Key Intermediates in Organocatalytic Michael Additions of Aldehydes to Nitroalkenes.
2013
Pause and play: dihydrooxazine oxides are stable intermediates that are protonated directly, without the intermediacy of the zwitterions, in organocatalytic Michael additions of aldehydes and nitroalkenes (see scheme, R=alkyl). Protonation of these species explains both the role of the acid co-catalyst in these reactions, and the observed stereochemistry when the reaction is conducted with α-alkylnitroalkenes.
Addition von Phosphor‐Nucleophilen an Benzothiet
1991
Addition Reactions of Phosphorus Nucleophiles to Benzothiete Trialkyl phosphites 4 add to the o-quinoid form 2 of benzothiete (1) to yield the phosphonates 6. An intermolecular migration of an alkyl group from oxygen to sulfur is the most important feature of this transformation. The rearrangement – related to the Arbuzov reaction – can be avoided in a two-step process by the subsequent action of PCl3 and alcohol; thus the phosphonates 10 are generated. Analogous to 2 6, dimethyl phenylphosphinate (11) furnishes 13. In contrast, the cyclic esters 14a–d form 2:1 adducts, namely the 12- to 15-membered heterocyclic compounds 17a – d. An intramolecular rearrangement in a 1:1 adduct is only obse…
Endgruppenuntersuchungen an isotaktischen Polystyrolen. VII. Mitt. über die stereospezifische Polymerisation von Styrol mit alkaliorganischen Verbind…
1963
Durch Polymerisation von Styrol mit optisch aktivem 2-Methylbutylnatrium oder -lithium konnen Polystyrole hergestellt werden, welche die Ebene des polarisierten Lichtes drehen; der gemessene Drehwert entspricht bei nicht zu hochmolekularen Polymeren einer 2-Methylbutylgruppe pro Makromolekul. Bei der Suche nach einer ungesattigten Endgruppe konnten weder mit einer infrarotspektroskopischen Kompensationsmethode noch durch eine Anlagerungsreaktion eines Siloxanmonohydrids Doppelbindungen in mit 2-Methylbutylnatrium hergestellten Polystyrolen nachgewiesen werden. Aus der Bestimmung der wachsenden Polystyrolmolekule mit Hilfe von MICHLERS Keton als Abbruchsreagenz ergibt sich, das der groste Te…
Glycidyl methacrylate derivatization of α,β-poly(N-hydroxyethyl)-dl-aspartamide and α,β-polyasparthydrazide
1997
Abstract α,β-Poly(N-hydroxyethyl)- dl -aspartamide (PHEA) and α,β-polyasparthydrazide (PAHy) are two synthetic macromolecules having many potential applications in the field of biomedical sciences. This paper describes the functionalization of PHEA and PAHy with glycidyl methacrylate (GMA), in order to introduce pendant double bonds in their chains. Derivatized PHEA and PAHy (samples PHG and PAG, respectively) at various GMA content have been obtained and characterized. It has been shown that the derivatization reaction can be controlled by varying some parameters as solvent, catalyst, pH, GMA concentration and reaction time. As expected, PAHy reacted more rapidly and more extensively than …
Unsaturated carboxylic acid dienolates. Addition to substituted cyclohexanones. Inverted kinetic and thermodynamic stereoselectivities.
1987
Abstract Addition of the lithium dienolate derived from crotonic acid to monosubstituted cyclohexanones occurs through the α and γ carbon atoms of the dienolate in the cold and on heating, respectively. For any regioselectivity, equatorial approach is found under kinetic conditions, but equilibration favours products from axial attack and selectivity may be inverted.
Trienediolates of hexadienoic acids in synthesis. synthesis of retinoic and nor-retinoic acids.
1993
Abstract Double deprotonation of either (E,E)-3-methyl-2,4-hexadienoic acid 2, or 4,6-dimethyldihydro-2-pyrone 3 generates apparently the same lithium trienediolate, which affords ω-hydroxy acids 9 on reaction with ketones 7. Hydroxy acids 9 are easily dehydrated to octatrienoic acids 5, which are structurally related to retinoic acid. Similarly, sorbic acid 1 leads to nor-retinoic acid analogs 6.