to undergo ring closing methathesis to yield ..

A versatile synthetic means for cyclic diblock copolymers has been developed by the combination of atom transfer radical polymerization (ATRP) and ring closing methathesis (RCM) techniques. Thus first, an A-B type allyl-telechelic diblock copolymer comprised of two different acrylate ester segment, i.e., poly(methyl acrylate-b-n-butyl acrylate), poly(MA-b-BA), was prepared via the ATRP of MA, followed by the addition of the second monomer, BA, with allyl bromide as an initiator and with allyltributylstannane as an end-capping reagent, respectively. Alternatively, an A-B-A type allyl-telechelic triblock copolymer comprised of poly(BA) and poly(ethylene oxide), poly(EO), segments was prepared via the ATRP of BA using a poly(EO) macroinitiator having 2-bromoisobutyryl end groups, followed by the end-capping reaction with allyltributylstannane. The subsequent RCM of the allyl-telechelic block copolymers under dilution in the presence of Grubbs catalyst could afford the corresponding A-B type cyclic diblock copolymers.

ring-closing methathesis | The Heterocyclist

Posts about ring-closing methathesis written by Will Pearson

followed by ring-closing methathesis to access ..

In devising a strategy for the total synthesis of the eudesmanes, we simplified our target to enone 5, which has been utilized in the preparation of structures such as 4, and itself embodies many features present in various family members (cf. 5 and 1, 2) (Figure 2). We envisioned that the stereochemistry of the C(7) substituent could arise by means of the diastereoselective hydrogenation of a substituted cyclohexene (i.e., 6), the stereochemical outcome of which would be controlled by the C(10) quaternary stereocenter. This cyclohexene could be obtainable from a ring-closing methathesis of triolefin 7, which would be derived from an appropriately substituted α-quaternary ketone (i.e., 8). Thus, the key control element in the design of this synthetic strategy is the C(10) quaternary stereocenter, and we therefore sought to develop an efficient and selective means for the preparation of this moiety.

Comparative Ring-Closing Methathesis ..

Macrocyclizations of intermediates 9-(m,n) were conducted on the resin at room temperature in CH2Cl2 using Hoveyda-Grubbs 2nd generation RCM catalyst [(1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(o-isopropoxyphenylmethylene)ruthenium] (). Except for substrates containing short alkenyl side chains (the peptide-peptoid hybrids containing either two residues of 8a or one residue each of 8a and 8b), the open chain precursors were completely consumed in the RCM reaction. The efficiency of ring closure was sequence-dependent, with members from the 2-series giving the highest percentage of expected ring-closed product. Finally, amino terminal acylation with FITC as described above and cleavage of peptides from the resin provided the target macrocyclic peptides 1-(m,n), 2-(m,n), 3-(m,n) and 4-(m,n) (). RCM is known to provide mixtures of alkenyl E/Z geometric isomers during the methathesis reaction. Previously reported examples of RCM macrocyclizations performed on large peptide substrates have highlighted the difficulties of obtaining defined E/Z geometries at the ring-forming alkenyl junction. Consistent with these prior studies, our current work does not explicitly define the geometries of RCM ring closure, nor does it extrapolate conformations of the resulting macrocycles.

ciguatoxin CTX3C - polycyclic ether - asymmetric alkylation - ring-closing methathesis - multiple asymmetric induction
T1 - Access to 1-hydroxymethylpyrrolizidines utilizing malate enolate-imine condensation and ring-closing methathesis

Mechanism of Ring Closing Metathesis

Asymmetric Conjugate Additions and Ru-Catalyzed Ring-Closing Methathesis," M

Ring Closing Metathesis Reaction Planning

New indenylidene Schiff Base Ru-based Catalysts for Ring Closing Methathesis

11.07 – Ring-closing Olefin Metathesis for Organic Synthesis