Oxygen Transfer Research Articles

Looking for improved strains of Azotobacter vineladii and favorable culture conditions yielding high‐molecular‐weight poly(3‐hydoxybutyrate)

AbstractBackgroundPoly(3‐hydroxybutyrate) (P3HB) is a polymer that presents properties similar to those of conventional plastics. The objective of the present study was to evaluate the influence of oxygen transfer rate (OTR) on the production and molecular weight of P3HB synthesized by the OP‐PhbP2− and OP‐PhbP3+ mutant strains of Azotobacter vinelandii, which have inactivated the gene that expresses the PhbP2 phasin and overexpresses the PhbP3 phasin genes, respectively.ResultsUnder high OTRmax (6.0 ± 0.04 mmol O2 L−1 h−1) mutant OP‐PhbP3+ exhibited a higher growth rate (0.12 ± 0.01 h−1) and P3HB production (6.77 ± 0.19 g L−1) than that achieved in the cultures using the OP‐PhbP2− mutant and OP wild‐type strains (5.0 ± 0.1 g L−1 for both strains). Under that condition, the OP‐PhbP3+ strain also exhibited a lower specific oxygen consumption rate. In contrast, under a low OTRmax (2.8 ± 0.06 mmol O2 L−1 h−1), the OP‐PhbP2− strain had a better performance, reaching 4.5 ± 0.35 g L−1 of P3HB, during the stationary phase (36–72 h). Both mutant strains produced a polymer with a high molecular weight (close to 8000 kDa), regardless of the OTR of the cultures, which remained constant throughout the fermentation. In contrast, the molecular weight produced by the OP strain was in the range 5500 to 6700 kDa under the two conditions evaluated.ConclusionOverall, our results revealed the biotechnological potential of using modified strains, which overexpress PhbP3 phasin or have inactivated the gene that expresses the PhbP2 phasin, for the production of P3HB, affording a higher molecular weight than that produced by the OP strain. © 2024 Society of Chemical Industry (SCI).

Influence of oxygen transfer performance on nitrogen metabolism and microbial community structure in an aerobic fluidized bed biofilm reactor under different aeration aperture

Influence of oxygen transfer performance on nitrogen metabolism and microbial community structure in an aerobic fluidized bed biofilm reactor under different aeration aperture

Exploration of the Out‐of‐Phase Phenomenon in Shake Flasks by CFD Calculations of Volumetric Power Input, kLa Value and Shear Rate at Elevated Viscosity

ABSTRACTCulture broth with secreted macromolecules and culture broth of filamentous fungi showing disperse growth exhibit elevated viscosity, usually with shear‐thinning flow behavior. High viscosity, however, poses a serious challenge in the production and research of these compounds and organisms. It commonly causes insufficient mixing and oxygen transfer in large‐ and small‐scale bioreactors. Computational Fluid dynamics (CFD) has been proven to be a valuable tool for the computation of important bioprocess parameters. The published literature for small‐scale shaken bioreactors, especially shake flasks, however, almost exclusively focuses on water‐like viscosity. In this paper, a previously published CFD model for 250 mL shake flasks was used to simulate experiments at high viscosities of up to 100 mPa·s. Compared to experimental data, the CFD model accurately predicted the liquid distribution and computed the volumetric power input with a deviation of less than 7% and the kLa value within a factor of two, compared to the kLa correlation from Henzler and Schedel. Furthermore, a novel approach to compute the shear rate was tested. Lastly, new insights into the out‐of‐phase phenomenon were gained. The presented data confirms the usefulness of the already established critical phase numbers of 0.91 and 1.26, while underlying the fundamentally smooth transition from in‐phase to out‐of‐phase operating conditions.

Thalassemia in Pakistan: Addressing a Genetic Health Crisis

Thalassemia, a genetic disorder usually caused by the defective genes. These genes are responsible for production of hemoglobin, a protein necessary for the transfer of oxygen in body through blood. Prevalence of thalassemia in Pakistan is concerning to a significant level. Global prevalence of this disease has affected millions of people and their lifestyles. Moreover, the disease leads to the burden on the diseased person’s family and the medical resources of the country, causing an alarming concern. The main issue of high prevalence of this disorder in Pakistan is associated with high percentage of cousin marriages. This cultural practice between the close relatives increases the chances of inheriting mutated genes into next generations. Each year more than 5000 children in Pakistan are born with disease. The rate of thalassemia is considerably higher in first cousin marriages (76.7%) than in second cousin marriages (23.3%) [1]. Furthermore, the inadequate spread of awareness among people and the lack of preventative measure by people is contributing to the increase in the number of thalassemia cases Thalassemic patients do require blood transfusion in an adequate to survive and live a normal life. Moreover, after transfusion they need financially draining therapies like iron chelation that is being required to manage the overload of iron in blood. The limited medical resources and poor infrastructure of hospitals and clinics in the rural areas can lead to the increase of complications then reducing the problems come with this disease. This kind of public healthcare system can affect the diseased individuals to level to develop life threatening problems such as stunted growth, and organ failures etc. To address this problem, a national program stating that genetic screening before marriage is necessary can lead to the reduction in the rate if this disease. Premarital screening for inherited diseases including Thalassemia is being carried out in middle east for last more than a decade. Some countries like Iran have overcome this problem to a great level by taking these kinds of initiatives, which shows that how important is it to detect the disease occurrence through premarital screening and counseling [2]. There should be campaigns for the public awareness highlighting the importance of genetic screening so that the cause of occurrence of this disorder can be decreased. Additionally, medical advancements have provided the hope. Despite being costly and scarce, for certain patients with thalassemia, bone marrow transplants (BMT) have proven to be a curative treatment, success rates for those who satisfy the right criteria, such as younger patients with matched related donors, range approximately between 80 and 95% [3]. Future advances in repairing genetic abnormalities at their origins may be possible thanks to emerging gene-editing technologies like CRISPR. To make these remedies available in Pakistan, however, significant funding for medical infrastructure and research is needed. Despite being avoidable, thalassemia will continue to take lives and put a burden on families and communities unless immediate action is taken. Pakistan can considerably lessen the impact of this genetic health disaster and clear the path for a healthier future by placing a high priority on education, early identification, and cutting-edge treatments.

Photochemical and Collision-Induced Cross-Linking of Asp, Glu, Asn, and Gln Residues in Peptide-Nitrile Imine Conjugate Ions in the Gas Phase.

Peptide conjugates furnished with a 2,5-diaryltetrazolecarbonyl tag at the C-terminal lysine, which we call peptide-tet-K, were found to undergo efficient cross-linking of Asp, Glu, Asn, and Gln residues to transient nitrile-imine intermediates produced by photodissociation and collision-induced dissociation (CID) of the tetrazole ring in gas-phase ions. UV photodissociation (UVPD) at 213 nm achieved cross-linking conversion yields of 37 and 61% for DAAAK-tet-K and EAAAK-tet-K, respectively. The yields for NAAAK-tet-K and QAAAK-tet-K were 29 and 57%, respectively. Even higher cross-link yields were found for CID-MS3 of stable denitrogenated ions, (peptide-tet-K-N2 + H)+, that were in the 69-83% range. Different types of cross-links were distinguished by CID-MSn that showed a distinct series of backbone fragment ions, loss of N-terminal groups, and loss of phenylhydrazine from the modified nitrile imines. The Asp and Glu side-chain carboxyl groups were major participants in cross-linking that resulted in proton and oxygen transfer to the nitrile imine group. Other types of cross-linking involved Asn and Gln CONH2 groups and backbone amides. Cyclic ion mobility-mass spectrometry was used to separate NAAAK-tet-K and QAAAK-tet-K conformers and products of their collision-induced denitrogenation. Linear nitrile-imine and cross-linked ion structures were identified by comparing the experimental collision cross sections (CCSexp) to those for structures obtained by combined Born-Oppenheimer molecular dynamics and density functional theory (DFT) calculations. The formation of cross-links was found to be energetically favorable and involved proton-facilitated nucleophilic attack at the nitrile-imine carbon atom.

Complications during extracorporeal membrane oxygenation transfer in Argentina: A multicenter observational study.

There is a lack of documented cases regarding complications during ECMO transfer in middle-income countries. Using portable ECMO devices facilitates patient transport but entails significantly higher costs, necessitating evidence of their practical utility. This study aims to describe complications during ECMO transfer in Argentina and to compare complication rates between the integrated portable ECMO and non-portable ECMO systems. A multicenter observational retrospective study was conducted across four high-complexity hospitals in Argentina. Patients over 18 years old who underwent ECMO transfer between January 2017 and July 2023 were included. Complications were classified based on the Ericsson severity classification, a widely accepted system that categorizes complications based on their severity and the need for immediate organ support. The effect of the ECMO systems (portable and non-portable ECMO system) on complication rates was assessed using logistic regression weighted by inverse probability weighting (IPWT) analysis after propensity score assessment to adjust for confounders. The study included 65 patients who were transferred for ECMO. Complications occurred in 40% (95%CI: 28%, 52%; n=26) of transfers, with grade 2 complications being the most prevalent at 20% (95%CI 11%, 32%; n=13). Integrated portable ECMO systems were associated with fewer complications during ECMO transfer, showing a crude OR of 0.25 (95%CI 0.08, 0.75), and after adjustment by IPWT, an OR of 0.27 (95%CI 0.08, 0.93). ECMO transfers in middle-income countries exhibit complication rates similar to those in high-income countries. Our study found fewer complications in transfers using integrated portable ECMO systems and those involving distances exceeding 100 km. These findings suggest that the use of portable ECMO systems, despite their higher costs, may be beneficial in reducing complications during patient transport in middle-income countries.

Comparison of waterline corrosion of a weathering steel in static and dynamic simulated seawater

Abstract Waterline corrosion behavior of a weathering steel in static and dynamic simulated seawater was studied by means of wire beam electrode (WBE), scanning electron microscopy, and Fourier transform infrared spectroscopy in this paper. The results show that the distribution of cathode and anode on WBE surface was relatively stable under static condition with large cathode and anode structure. The region near the waterline was always a stable cathode, and the total anode current density decreased with time and basically stabilized after 6 days. Under dynamic condition, a large anode structure was formed on the WBE surface within 1 day, and the anodic current density rapidly decreased with time. The anode area gradually decreased and the WBE surface showed an alternating distribution of small anode and cathode after 3 days. The total anodic current density continued to decrease with time after 6 days. Under dynamic condition, the mass transfer of oxygen and other substances related to electrode reactions was accelerated, so that the anode surface was rapidly corroded in the early stage of immersion and covered by denser corrosion products, resulting in a positive shift in the potential and electrode reversal of some anode areas in the later stage.

Physicochemical wastewater treatment improvement by hydrodynamic cavitation nanobubbles

Hydrodynamic nanobubble aeration is proposed as an innovative approach to enhancing physicochemical wastewater treatment. Integrating a novel cavitation system to replace conventional aeration significantly improves standard oxygen transfer efficiency and energy consumption. The changes in size and surface charge of air, oxygen (O2), ozone (O3), and chitosan nanobubbles were studied as a function of the reactor diameter. Interestingly, it was found that increasing the radial dispersion length had no significant effect on the measured parameters. Flotation, Coagulation-flocculation (CF), and Advanced Oxidation (AOPs) processes of municipal wastewater comparing convective air and O3 NBs aeration were carried out at pilot plant scale. The use of O3 NBs in the flotation process improves 160 % the suspended solids removal compared to the air-NBs- process. The CF process was evaluated by adding a chitosan dose to the convective processes and monitoring the water quality parameters in real-time. The results demonstrated that the interaction of chitosan with O3 NBs eliminates more than 80 % of the initial chemical oxygen demand (COD). Finally, the AOP carried out with O3 NBs reaches a removal efficiency of 99.8 % total suspended solids and 90 % COD. This modular system presents a practical and efficient alternative for removing municipal and industrial wastewater contaminants.

From Global to Local: A Population Balance Approach for the Prediction of Oxygen Transfer in Aeration Operations

From Global to Local: A Population Balance Approach for the Prediction of Oxygen Transfer in Aeration Operations

Boosting the power density of direct borohydride fuel cells to >600 mW cm−2 by cathode water management

Direct borohydride fuel cell (DBFC) has garnered significant interest due to its high energy density. However, the power density remains insufficient for commercial applications. Lots of works have been conducted on the kinetics of the anode reaction, while little attention has been devoted to cathode water management which is important issue for direct liquid fuel cell. Herein, a new structure gas diffusion layer (GDL) with hetero-junction double microporous layer (HJD-MPL) is developed. Utilizing the HJD-MPL structure, achieving a peak power density of 688 mW cm−2 at 80 °C, which exceeds the literature reports (453 mW cm−2). With higher porosity, permeability and stronger gradient capillary force, the oxygen transfer resistance is reduced from 75.5 s cm−1 of commercial GDL to 24.4 s cm−1. This study offers new insight into DBFCs, emphasizing cathode engineering to advance more effective and reliable direct liquid fuel cell technologies.

Novel sparging strategies to enhance dissolved carbon dioxide stripping in industrial scale stirred tank reactors

Aerated stirred tank reactors are widely used in bio-process engineering and pharmaceutical industries. To supply the organisms with oxygen and control the pH value, oxygen is transferred from air bubbles into the liquid phase, and, at the same time, carbon dioxide is stripped from the liquid phase with the same gas bubbles. The volumetric mass transfer coefficients for oxygen and carbon dioxide are, therefore, of crucial importance for the design and scale-up of aerated stirred tank reactors. In this experimental work, the volumetric mass transfer coefficients for oxygen and carbon dioxide are investigated simultaneously to study their mutual influence. The mass transfer performance for oxygen and carbon dioxide is conducted in stirred tank reactors on the 3 L laboratory scale, 30 L pilot scale, and 15,000 L production scale. First, the influence of dissolved carbon dioxide on the oxygen mass transfer performance is investigated in a 30 L pilot scale stirred tank reactor. The results show that the volumetric mass transfer coefficient of oxygen is not affected by the concentration of dissolved carbon dioxide, but the total mass flux of oxygen decreases with increasing carbon dioxide concentration due to the decreasing partial pressure difference. With rising gassing rate and volumetric power input, both mass transfer coefficients for oxygen and carbon dioxide show the same increasing trend. Although this trend can also be observed when scaling down to the 3 L laboratory scale reactor, a significantly different effect must be considered for the scale-up to the 15,000 L industrial scale reactor. The limited absorption capacity for carbon dioxide of the gas bubbles during the long residence time in the industrial scale reactor is noticeable here, which is why the specific interfacial area is of negligible importance. This effect is used to develop a method for independent control of oxygen and carbon dioxide mass transfer performance on an industrial scale and to increase the mass transfer performance for carbon dioxide by up to 25%.

Flow Field of Supersonic Oxygen Jet Generated by Various Wear Lengths at the Laval Nozzle Exit

As a main apparatus, the oxygen lance is used to deliver the oxygen element and transfer kinetic energy into the molten bath in the steelmaking process. However, the Laval nozzle exit would be gradually worn out during the service life, which suppresses the performance of the oxygen lance. This paper investigated three different wear length (Lw) conditions at the exit of the Laval nozzle through numerical simulations and high-temperature experiments with various oxygen flow rates. The result showed that the entrainment of the ambient gas was the key factor of the wear phenomenon for the Laval nozzle exit. The maximum total temperature of the gas phase at the Laval nozzle exit formed by the Lw of 0 mm, 2 mm, and 4 mm were 300 K, 959 K, and 1700 K, respectively. Thus, by increasing the Lw value, the total temperature of the gas phase was rapidly improved at the exit of the Laval nozzle, which further accelerated the wear phenomenon at the exit of the Laval nozzle. Besides, axial velocities at the end of the potential core formed by the Lw of 0 mm, 2 mm, and 4 mm were 483.7 m/s, 480.0 m/s, and 478.7 m/s, respectively. As a result, the wear phenomenon reduced the impaction ability of the oxygen jet, which suppressed the impaction depth and radius, resulting in a smaller droplet generation rate.

From coffee waste to nutritional gold: bioreactor cultivation of single‐cell protein from Candida sorboxylosa

AbstractBACKGROUNDIndustrial effluents are continuously discharged into the environment. These wastewaters contain valuable compounds that can be reused for biotechnological applications. Coffee wastewater (CWW) is a powerful effluent that can be used for single‐cell protein (SCP) production reaching important content (up to 80%). Several yeast species can be used for SCP production, but Candida species are commonly applied for this purpose (17 species reported including the novel C. sorboxylosa). In addition, SCP can be produced in bioreactors under controlled conditions under three operation modes. Thus, batch mode is frequently used but continuous mode presents interesting advantages in economic terms, although it has been poorly applied in SCP production.RESULTSThe initial evaluation under batch operation mode showed that volumetric oxygen transfer coefficient (kLa of 101 h−1) improved biomass production (1.39 g L−1) and SCP yield (59.9%) in C. sorboxylosa. Thus, continuous mode was established at selected kLa and feeding with optimized medium composed of 87.5% (v/v) CWW, 1.38 g L−1 yeast extract, and 7.24 g L−1 (NH4)2SO4, in order to provided necessary nutrients. In this sense, the process presented higher values in dry cell weight and SCP productivity (0.57 and 0.29 g L−1·h, respectively), achieving a 3.35‐ and 2.90‐fold increase in biomass and protein productivity, respectively, compared to batch mode. The SCP from C. sorboxylosa exhibited an interesting essential amino acid profile under continuous mode (33.704%).CONCLUSIONThe bioprocess highlights several advantages during bioreactor cultivation, including: (i) reduced energy consumption for temperature control; (ii) successful establishment of an initial continuous operation mode with promising performance; and (iii) SCP from C. sorboxylosa exhibited a notable composition of essential amino acids, which could be beneficial for potential use in animal feed. © 2024 Society of Chemical Industry (SCI).

Insight into interactive synergy of MoS2@CoNC for peroxymonosulfate activation: From bath experiments to continuous flow experiments

As catalysts for peroxymomosulfate (PMS) activation, several carbon materials derived from MOFs have gained considerable attention. Despite this, Fenton-like reactions have always been limited by cycle efficiency of metal’s valence state. In this study, a novel catalyst (MoS2@CoNC), Molybdenum disulfide (MoS2) modified CoNC (derived from ZIF-67), was successfully synthesized. Catalytic experiments indicated that the carbamazepine (CBZ) degradation efficiency could be enhanced in the MoS2@CoNC-PMS process. Moreover, PMS decomposition also exhibited outstanding performance compared with other processes. Various quenching experiments and ESR analyses indicated that CBZ degradation is mainly caused by nonradical oxidation (86.10 %). In addition, Density Functional Theory (DFT), in-situ Raman, and in-situ FTIR were employed to elucidate PMS activation mechanism. The generation pathways of singlet oxygen (1O2), cobalt-oxo species (CoVI = O), and electron transfer were systematically elaborated. X-ray Photoelectron Spectroscopy (XPS) analysis identified unsaturated S as a significant factor contributing to MoS2@CoNC stability. Further investigation into CBZ degradation was conducted using DFT and LC-MS. The toxicity of intermediates was also assessed through TEST and bean sprout cultivation. Additionally, a continuous flow experiment is performed to evaluate the practical application of MoS2@CoNC-PMS. After 10 h, CBZ removal efficiency is approximately maintained at 90 %. Water matrix effects and multi-pollutant degradation also determined that the MoS2@CoNC-PMS process is a promising method for pollutants degradation.

Model development for real oxygen delignification processes

Previous extensive work has been done on modeling the oxygen delignification process, based on how the basic parameters, i.e., temperature, kappa number, concentration of alkali, and concentration of oxygen, affect the delignification rate. However, these models are not used extensively to evaluate the performance of real processes, primarily because they have not been able to properly consider all the essential issues affecting delignification in practice. Such issues include the mass transfer and consumption of oxygen, which defines the concentration of dissolved oxygen in the process, and the effect of that concentration on the delignification rate. In this paper, a new way to model the oxygen delignification process is used in which these parameters, among other smaller matters, are taken into account. The basic model and its parameters were defined by the information obtained from the literature, delignification made in the laboratory tests, and mill processes and mill tests. An essential aspect of these studies was the information obtained from the oxygen concentration measured in the residual gas obtained from the top of the reactor. With the aid of this measurement, it was possible to define more accurately the consumption of oxygen and partial pressure of oxygen that define the concentration of dissolved oxygen in the reactor. Using mill experiments, a model was formed that predicts the operation of the oxygen delignification process. The model was used to show how much the process could be improved by optimizing the charge of the oxygen. The mill experiments also confirmed that mass transfer of oxygen is modeled correctly enough, except when the charge of oxygen is very low and/or the mixing is not efficient enough. In that case, there is variation in the concentration of oxygen in the process that should be taken into account in the modeling.

Surface electric fields-enhanced biochar: A dual-action adsorbent and PMS activator for sulfamethoxazole removal

Integrating adsorption with advanced oxidation processes offers significant advantages over conventional single-stage wastewater treatment methodologies. Herein, this study successfully synthesized nitrogen-boron codoped metal-free biochar at 700 °C (700NBBC). 700NBBC effectively eliminates sulfamethoxazole (SMX) from water through a synergistic adsorption-oxidation process, showcasing robust resistance to interference and broad pH tolerance. Characterizations and experimental outcomes indicate that 700NBBC primarily adsorbs SMX through a monolayer surface chemical adsorption mechanism and activates persulfate (PMS) to oxidize SMX via a non-radical mechanism, which includes the generation of singlet oxygen (1O2) and electron transfer processes. Density functional theory calculations elucidate that N and B doping regulate the local electronic environment at biochar surface, enhancing the adsorption energy between biochar and PMS while effectively catalyzing PMS cleavage to generate 1O2. This research offers fresh perspectives on the critical role of heteroatom doping in regulating reactive oxygen species generation within biochar.

Enhancement of CO2 adsorption and oxygen transfer properties on γ-Al2O3 support through surface modification with MgO-ZrO2 for coke suppression over Ni catalyst in CO2 reforming of methane

This work focuses on employing commercial γ-Al2O3 for surface modification with MgO-ZrO2 mixed oxide to enhance the potential of CO2 adsorption and oxygen mobility. This enhancement facilitates its application as a support in catalysts for CO2 utilization such as CO2 reforming of methane (CRM). To achieve this perspective, γ-Al2O3 was modified with 10 wt.% of various MgO and ZrO2 contents (MgO:ZrO2= 10:0, 9:1,7:3, 5:5, 3:7, 1:9 and 0:10) using the impregnation method. All samples including unmodified γ-Al2O3 (Al) were characterized. Due to the increase in basicity and oxygen transfer around the surface, the improvement of the CO2 adsorption was observed on γ-Al2O3 modified with 9 wt.% MgO-1 wt.% ZrO2 (9Mg1ZrAl) and 10 wt.% MgO (10MgAl), respectively. An application of these two superior samples as a support of 10 wt.% Ni (10Ni) catalysts for CRM was investigated and compared with an unmodified γ-Al2O3. Characterization results suggest the formation of NiO-MgO solid solution at the surface due to the decrease in metal-support interaction and the increase in metal dispersion. The Ni catalysts with the surface-modified support show higher CO2 activity that raises carbon deposition resistance. The greatest coke prevention was observed on 10Ni/9Mg1ZrAl that lowers the coke deposition by 42 % compared to 10Ni/Al. It indicates that the composition of this modification allowed very low ZrO2 portion to merge with MgO and MgO to form solid solution with NiO. This enables the 10Ni/9Mg1ZrAl catalyst to generate labile oxygens which can be conveyed to the Ni metal sites on the catalyst.

Biokinetic modeling approach to investigate the impact of rotational speed variations in modified rotating biological contactors for palm oil mill effluent treatment

Palm oil mill effluent (POME) contains high organic content, posing significant environmental challenges that demand effective treatment solutions. Conventional rotating biological contactor (RBC) used for POME treatment are limited by insufficient surface area for microbial growth and inefficient oxygen transfer, limiting their effectiveness. This study enhances RBC systems by incorporating bioballs to increase microbial attachment surfaces and improve treatment performance. Experiments were conducted at various rotational speeds, and biokinetic modeling was applied under unsteady-state conditions. The results showed that the RBC operated at 3 rpm achieved the highest removal efficiencies, with 67.4 % for SCOD, 92.4 % for TSS, and 73 % for NH3. The biokinetic model revealed that rotational speed did not significantly impact oxygen transfer, mainly during the aeration phase. Lower speeds optimized substrate degradation and microbial growth, while higher speeds caused biofilm detachment. The innovative use of bioballs improves POME treatment efficiency at lower speeds, offering a cost-effective solution.

Generation of Bis(pentafluorophenyl)boron Enolates from Alkynes and Their Catalyst‐Free Alkyne Coupling

Carbon‐carbon bond forming reactions are powerful synthetic tools for constructing organic molecular frameworks. In this study, strongly Lewis acidic bis(pentafluorophenyl)boron enolates were generated from alkynes through oxygen transfer from 2,6‐dibromopyridine N‐oxide using tris(pentafluorophenyl)borane [B(C6F5)3]. Boron enolates were highly reactive owing to the strong acidity of the boron centers, and thus immediately coupled with alkynes. N‐Ethynylphthalimide reacted as an alkyne with 2,6‐dibromopyridine N‐oxide and B(C6F5)3 to form a semi‐stable bis(pentafluorophenyl)boron enolate through the coordination of the carbonyl group to the boron center. This enolate underwent coupling with another alkyne.

Generation of Bis(pentafluorophenyl)boron Enolates from Alkynes and Their Catalyst-Free Alkyne Coupling.

Carbon-carbon bond forming reactions are powerful synthetic tools for constructing organic molecular frameworks. In this study, strongly Lewis acidic bis(pentafluorophenyl)boron enolates were generated from alkynes through oxygen transfer from 2,6-dibromopyridine N-oxide using tris(pentafluorophenyl)borane [B(C6F5)3]. Boron enolates were highly reactive owing to the strong Lewis acidity of the boron centers, and thus immediately coupled with alkynes. N-Ethynylphthalimide reacted as an alkyne with 2,6-dibromopyridine N-oxide and B(C6F5)3 to form a semi-stable bis(pentafluorophenyl)boron enolate through the coordination of the carbonyl group to the boron center. This enolate underwent coupling with another alkyne.