17 research outputs found
Ring-Opening Metathesis of Bulky Norbornene Monomers and the Radical-Mediated Hydrophosphonation of Olefins
No full textThis thesis discusses two major topics: the ring-opening metathesis polymerization (ROMP) of bulky monomers and the radical-mediated hydrophosphonation of olefins. The research into the ROMP of bulky monomers is further divided into three chapters: wedge-shaped monomers, the alternating copolymerization of 1-methyloxanorbornene derivatives with cyclooctene, and the kinetic resolution polymerization of 1-methyloxanorbornene derivatives. The wedge-shaped monomers can be polymerized into diblock copolymers that possess photonic crystal properties. The alternating copolymerization of 1-methyloxanorbornene derivatives with cyclooctene is performed with > 90% alternation via two different routes: typical alternating copolymerization and a sequence editing approach. The kinetic resolution polymerization of these same 1-methyloxanorbornene monomers achieves only modest selectivity (S=4), but there is evidence that the growing polymer chain forms a helix that influences the selectivity of the resolution. The last topic is the radical-mediated hydrophosphonation of olefins. This synthetic method provides access to Wittig reagents that are capable of highly cis-selective olefinations of aldehydes
Radical-Mediated Anti-Markovnikov Hydrophosphonation of Olefins
No full textThe radical-mediated addition of triphenylphosphonium tetrafluoroborate to olefins (hydrophosphonation) is reported. Both standard radical initiators and photochemical conditions are effective, up to the gram scale. The phosphonium salts are shown to serve as Z-selective Wittig olefination reagents, even without purification
Radical-Mediated Anti-Markovnikov Hydrophosphonation of Olefins
No full textThe radical-mediated addition of triphenylphosphonium tetrafluoroborate to olefins (hydrophosphonation) is reported. Both standard radical initiators and photochemical conditions are effective, up to the gram scale. The phosphonium salts are shown to serve as Z-selective Wittig olefination reagents, even without purification
New Single-Phase Retarded Acid System Boosts Production after Acid Fracturing in Kazakhstan
No full textAbstract
The use of conventional acid systems in high-temperature, fast-reactive carbonate reservoirs limits the effectiveness of matrix acidizing and acid fracturing. Therefore, during acid stimulation in such conditions, acids with retarded reaction are usually recommended. Industry-employed retarded acid systems have several significant drawbacks—they either dissolve lower rock volume or have higher friction and are more complex to mix than the standard hydrochloric acid system. The introduction of a new single-phase retarded acid enabled minimizing these drawbacks. The sustained increase in productivity index (PI) after the acid fracturing and matrix acidizing treatments under high-pressure/high-temperature conditions was achieved. The treatments were performed on exploration wells drilled in carbonate oil fields of the pre-Caspian and Mangystau oil-bearing provinces of West Kazakhstan.</jats:p
Catalyst-Dependent Routes to Ring-Opening Metathesis Alternating Copolymers of Substituted Oxanorbornenes and Cyclooctene
No full textThe
alternating copolymerization of cis-cyclooctene and 1-substituted
oxanorbornenes with commercially available ruthenium-based olefin
metathesis catalysts was investigated. We determined that RuCl2(CHPh)(PCy3)2
performs a standard alternating copolymerization with these monomers.
Unexpectedly, another route to the desired alternating copolymer was
revealed. The “sequence editing” route involves the
initial polymerization of cis-cyclooctene, followed
a ring-opening cross metathesis step that introduces the 1-substituted
oxanorbornene monomer in the polycyclooctene chain and largely avoids
oxanorborene homopolymerization. Selectivity for alternating diads
in the polymer exceeds 90%. Polymer molecular weight can be controlled
by linear olefin chain-transfer reagents during sequence editing
Inhibition of HIF-1 alpha by PX-478 enhances the anti-tumor effect of gemcitabine by inducing immunogenic cell death in pancreatic ductal adenocarcinoma
No full textThis is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use,
distribution, and reproduction in any medium, provided the original author and source are credited
Partial Kinetic Resolution of Oxanorbornenes by Ring-Opening Metathesis Polymerization with a Chiral Ruthenium Initiator
No full textWe
report the first kinetic resolution by ring-opening metathesis
polymerization (KR-ROMP). The polymerization profile showed a solvent-dependent
variation of selectivity (S) over the course of the
reaction. In tetrahydrofuran and dichloromethane, the resolution selectivity
increased over the course of the reaction, while in toluene the selectivity
was much higher in the beginning of the reaction and decreased throughout.
Evidence suggests that the change in selectivity might be attributed
to the chiral secondary structure of the growing polymer chain
