Computational Insights into Intramolecular Cross-Coupling of Quaternary Borate Salts

Cross-coupling reactions for C-C bond formation represent a cornerstone of organic synthesis. In most cases, they make use of transition metals, which has several downsides. Recently, metal-free alternatives relying on electrochemistry have gained interest. One example of such a reaction is the oxidation of tetraorganoborate salts that initiates aryl-aryl and aryl-alkenyl couplings with promising selectivities. This work investigates the mechanism of this reaction computationally using density functional and coupled-cluster theory. Our calculations reveal a distinct difference between aryl-alkenyl and aryl-aryl couplings: While C-C bond formation occurs irreversibly and without an energy barrier if an alkenyl residue is involved, many intermediates can be identified in aryl-aryl couplings. In the latter case, intramolecular transitions between reaction paths leading to different products are possible. Based on the energy differences between these intermediates, we develop a kinetic model to estimate product distributions for aryl-aryl couplings.<br>

Computational Insights into Intramolecular Cross-Coupling of Quaternary Borate Salts

Cross-coupling reactions for C-C bond formation represent a cornerstone of organic synthesis. In most cases, they make use of transition metals, which has several downsides. Recently, metal-free alternatives relying on electrochemistry have gained interest. One example of such a reaction is the oxidation of tetraorganoborate salts that initiates aryl-aryl and aryl-alkenyl couplings with promising selectivities. This work investigates the mechanism of this reaction computationally using density functional and coupled-cluster theory. Our calculations reveal a distinct difference between aryl-alkenyl and aryl-aryl couplings: While C-C bond formation occurs irreversibly and without an energy barrier if an alkenyl residue is involved, many intermediates can be identified in aryl-aryl couplings. In the latter case, intramolecular transitions between reaction paths leading to different products are possible. Based on the energy differences between these intermediates, we develop a kinetic model to estimate product distributions for aryl-aryl couplings.<br>

Computational Insights into Intramolecular Cross-Coupling of Quaternary Borate Salts

Cross-coupling reactions for C-C bond formation represent a cornerstone of organic synthesis. In most cases, they make use of transition metals, which has several downsides. Recently, metal-free alternatives relying on electrochemistry have gained interest. One example of such a reaction is the oxidation of tetraorganoborate salts that initiates aryl-aryl and aryl-alkenyl couplings with promising selectivities. This work investigates the mechanism of this reaction computationally using density functional and coupled-cluster theory. Our calculations reveal a distinct difference between aryl-alkenyl and aryl-aryl couplings: While C-C bond formation occurs irreversibly and without an energy barrier if an alkenyl residue is involved, many intermediates can be identified in aryl-aryl couplings. In the latter case, intramolecular transitions between reaction paths leading to different products are possible. Based on the energy differences between these intermediates, we develop a kinetic model to estimate product distributions for aryl-aryl couplings.<br>

Highly Effective Sensitizers Based on Merocyanine Dyes for Visible Light Initiated Radical Polymerization

The 5-(4-substituted-arylidene)-1,3-dimethylpyrimidine-2,4,6-triones were tested as visible light sensitizers for phenyltrialkylborate salts applied to initiate polymerization processes. The initiation occurs as a result of photoinduced electron transfer from the borate salt to the merocyanine dye. The main factor that facilitates the step of the reaction is the free energy change for electron transfer. Its value is favorable according to the reduction properties of the dyes influenced by the type of amino groups and the oxidation potentials of the borate salts. The observed bleaching of the dyes during photopolymerization affects the yield of both the alkyl radical and sensitizer-based radical formation and thus the efficiency of the photopolymerization.

Development of Tetraarylphosphonium/Tetrakis(pentafluorophenyl)borate (TAPR/TFAB) salts as non-aqueous electrolytes for organic redox flow batteries

A series of weakly coordinating cations/anions (TAPR/TFAB) ion pairs are, herein, being proposed as non-aqueous electrolytes for high capacity ORFBs. These were accessed via a Palladiumcatalyzed approach followed by the simple filtration/isolation of the product. These substituted tetraarylphosphonium/tetrakis(pentafluorophenyl)borate salts 1-4 where the substituents are a pmethoxy (1), a 3,4-dimethoxy (2), a p-phenyl (3), and a p-trimethylsilylacetylene (TMSA) (4) have potential use in several industries owing to their unique solubility in low polarity solvents. These salts constitute a new class of molecular ion pairs which can promote charge dissociation even in low polarity solvents because of their large size and bulkiness. The result being an increased conductivity in those media that can be useful for electrochemistry, advances in catalysis, battery technology, petroleum handling etc. This work supports the national security goal of fostering the development of affordable, clean and renewable energy source and storage.

Susceptibility of Environmentally Friendly Sheep Wool Insulation Panels to the Common Clothes Moth Tineola bisselliella in Laboratory Assays

In this study the resistance opposed to Tineola bisselliella larvae by a commercial sheep-wool panel incorporating borate salts was determined under laboratory conditions. The susceptibility of clothes moth larvae to different concentrations of disodium octaborate tetrahydrate (DOT) incorporated in pure wool was also determined. The commercial wool panel showed a remarkable resistance to moth attack compared with pure untreated wool, and the damage to panel samples was limited to their surface. As a result of bioassays exposing larvae to pure wool treated with DOT, a concentration dependent effect was observed, achieving a good efficacy at an application rate between 40–100 mg/mL. This study highlights the need to protect wool-based construction material with appropriate insecticidal (antifeedant or repellent) substances and supports the development of eco-sustainable solutions.