Several
low-molar-mass alkyl iodides were studied as initiating
dormant species in living radical polymerization with organic catalysts.
Primary, secondary, and tertiary alkyl iodides with different stabilizing
groups (ester, phenyl, and cyano groups) were systematically studied
for the rational design of initiating alkyl iodides. The activation
rate constants of these alkyl iodides were experimentally determined
for quantitative comparison. These alkyl iodides were used in the
polymerizations of methyl methacrylate and butyl acrylate to examine
their initiation ability in these polymerizations. A telechelic polymer
was prepared using an alkyl iodide with a functional group. Alkyl
iodides with multi-initiating sites were also studied.
A formal synthesis of the antitumor diterpenoid paclitaxel (Taxol) is described. The ABC ring of paclitaxel, synthesized starting from 1,3-cyclohexanedione and tri-O-acetyl-d-glucal by SmI2-mediated cyclization as the key transformation, was successfully converted to Takahashi's tetracyclic oxetane intermediate. A double Chugaev reaction was employed for introduction of the strained bridgehead olefin, and stereoselective formation of the oxetane ring afforded the known synthetic intermediate, completing the formal synthesis of paclitaxel.
A convergent synthesis of the ABC ring of antitumor natural product paclitaxel (Taxol) is described. SmI2-mediated reductive cyclization of an allylic benzoate possessing an aldehyde function, synthesized from tri-O-acetyl-d-glucal and 1,3-cyclohexanedione, smoothly afforded the highly strained 6-8-6 tricarbocyclic structure in 66% yield.
Temperature-selective radical generation from a newly designed alkyl diiodide (I-R -R -I) was studied. R -I and I-R had different reactivities for generating alkyl radicals in the presence of a tetraoctylammonium iodide (ONI) catalyst. Taking advantage of the temperature selectivity, we used the alkyl diiodide as a dual initiator in ONI-catalyzed living radical polymerization to uniquely synthesize CABC non-symmetric multi-block copolymers. Because of their non-symmetric structure, CABC multi-block copolymers form unique assemblies, that is, Janus-type particles with hetero-segment coronas and flower-like particles with hetero-segment petals.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.