Showing papers by "Tae-Lim Choi published in 2011"

Ultrafast cyclopolymerization for polyene synthesis: living polymerization to dendronized polymers.

Abstract: We discovered that ultrafast cyclopolymerization of 1,6-heptadiyne derivatives reached completion in 1 min using a third-generation Grubbs catalyst. After optimization, this superior catalyst selectively produced conjugated polymers having a five-membered-ring structure with excellent molecular weight control and narrow polydispersity index (PDI). This living polymerization allowed us to prepare fully conjugated diblock copolymers with narrow PDIs. Lastly, this catalyst was active enough to polymerize macromonomers with G-3 dendrons in a living manner as well. This dendronized polymer with a highly regioregular polymer backbone and bulky dendrons was visualized by atomic force microscopy, which revealed the structure of a single molecular wire surrounded by insulating dendrons.

Synthesis of fused multicyclic compounds containing macrocycles by dienyne ring-closing metathesis and Diels-Alder reactions.

Abstract: Fused bicyclic compounds comprising small and large rings were synthesised by dienyne ring-closing metathesis (RCM) using Grubbs’ catalyst By taking advantage of faster small ring cyclisation compared with macrocyclisation, single isomers were obtained rather than mixtures of two isomers with different ring sizes Using this process, various fused bicyclic compounds comprising small rings (5–7- membered) and large rings (14–17- membered) were obtained By increasing reaction temperature and catalyst loading, the product conversion was improved in a predicted manner This method produced E-olefins on the macrocycles with high selectivity Also, the selectivity issues of tandem RCM for the synthesis of fused bicyclic compounds comprising small and medium rings were investigated Lastly, the prepared bicyclic compounds with small and large rings contained 1, 3-dienes that underwent a further modification reaction, such as Diels–Alder, to produce more complex compounds These Diels–Alder reactions produced tri- and tetracyclic compounds containing a macrocycle with single diastereomers, suggesting that the methodology demonstrated here could be a powerful tool for rapid preparation of highly complex molecules

Synthesis of Fused Multicyclic Compounds Containing Macrocycles by Dienyne Ring-Closing Metathesis and Diels—Alder Reactions.

Abstract: RCM and Diels—Alder reactions are combined in an one-pot approach to give complex heterocyclic compounds, e.g. (XI).