Search results for "metathesis"
showing 10 items of 150 documents
Synthesis and characterization of amphiphilic comb-polymers via ring-opening metathesis polymerization of exo,exo-5,6-bis(alkoxymethyl)-7-oxabicyclo[…
1994
A number of exo,exo-5,6-bis(alkoxymethyl)-7-oxabicyclo[2.2.1]hept-2-enes (exo,exo-5,6-bis(alkoxymethyl)-7-oxanorbornenes) with long alkyl chains were prepared by reduction of the Diels-Alder adduct of furan and maleic anhydride, followed by alkylation with a series of different n-alkylbromides. These monomers were polymerized via ring-opening metathesis polymerization (ROMP) catalyzed by ruthenium trichloride in ethanolic solution. Contrary to a helical conformation as it was predicted by a previous molecular model study the poly(7-oxanorbornenes) adopt a coil conformation in solution. In bulk the materials show side chain crystallization.
Joining Two Natural Motifs: Catechol-Containing Poly(phosphoester)s.
2017
Numerous catechol-containing polymers, including biodegradable polymers, are currently heavily discussed for modern biomaterials. However, there is no report combining poly(phosphoester)s (PPEs) with catechols. Adhesive PPEs have been prepared via acyclic diene metathesis polymerization. A novel acetal-protected catechol phosphate monomer was homo- and copolymerized with phosphoester comonomers with molecular weights up to 42000 g/mol. Quantitative release of the catechols was achieved by careful hydrolysis of the acetal groups without backbone degradation. Degradation of the PPEs under basic conditions revealed complete and statistical degradation of the phosphotri- to phosphodiesters. In …
Templated synthesis of a large and flexible covalent porphyrinic cage bearing orthogonal recognition sites.
2012
A large covalent cage incorporating two porphyrins attached by four long and flexible polyether chains each bearing two 3-pyridyl ligands was synthesized from a DABCO-templated olefin metathesis reaction. The X-ray structure of the cage with the DABCO coordinated inside the cavity to the two zinc(II) porphyrins reveals a highly symmetric structure.
ChemInform Abstract: Cross-Metathesis Reactions as an Efficient Tool in the Synthesis of Fluorinated Cyclic β-Amino Acids.
2009
The synthesis of enantiomerically pure, cyclic, gamma,gamma-difluorinated beta-amino acids with various ring sizes has been carried out with a cross-metathesis (CM) reaction being one of the key steps, followed by a Dieckmann-type condensation to bring about the cyclization. Subsequent catalytic hydrogenation under microwave irradiation with (-)-8-phenylmenthol as a chiral auxiliary led to the successful chemo- and diastereoselective chemical reduction of the resulting cyclic beta-enamino esters. The efficiency and scope of the CM reaction with different types of fluorinated imidoyl chlorides and unsaturated esters has also been studied in order to determine the optimal reaction conditions …
Asymmetric Allylation/RCM-Mediated Synthesis of Fluorinated Benzo-Fused Bicyclic Homoallylic Amines As Dihydronaphthalene Derivatives
2016
Enantiomerically enriched fluorinated benzo-fused bicyclic homoallylic amities have been synthesized through an asymmetric allylation/ring closing metathesis (RCM) sequence. This sequence has been carried out using alpha-trifluoromethylstyrene derivatives as key intermediates, synthesized by microwave radiation. The great deactivating effect exerted by such substituents has been brought to light by a comparative study.
ChemInform Abstract: Synthesis of Fluorinated and Non-Fluorinated Bicyclic Amidines Through Ring-Closing Metathesis.
2012
Condensation of unsaturated esters (I) and (VII) with 1,2-diamines proceeds in the presence of trimethylaluminum providing imidazolines (III) and (VIII) which are further allylated giving suitable dienes (V) and (IX).
ChemInform Abstract: Asymmetric Synthesis of Fluorinated Amino Macrolactones Through Ring-Closing Metathesis.
2008
The synthesis of new chiral fluorinated amino and azamacrolactones of types 1 and 2 is described. A ring-closing metathesis (RCM) reaction constitutes the key step in this methodology, which uses fluorinated amino alcohols 7 as starting materials. The influence of the CF2 group, which is located in the alpha-position relative to the carbon bearing the amino group, on the efficiency of the RCM reaction is noteworthy. This method allows for the preparation of the desired fluorinated macrolactones in excellent yields.
ChemInform Abstract: An Approach to 2,4-Substituted Pyrazolo[1,5-a]pyridines and Pyrazolo[1,5-a]azepines by Ring-Closing Metathesis.
2014
Based on the title approach, the diastereoselective synthesis of potential peptidomimetics [(XI) and (XIV)] is described.
ω-Alkenylallylboronates: Design, Synthesis, and Application to the Asymmetric Allylation/RCM Tandem Sequence
2021
P. B. thanks the Spanish MINECO for a Ramón y Cajal contract (RyC-2016-20951). M.N.G. thanks the University of Bath for financial support.