Synthesis of Heterocycles from Potassium Trifluoro(pyrimidin-4-yl)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>

Download Full-text

Computational Insights into Intramolecular Cross-Coupling of Quaternary Borate Salts

10.26434/chemrxiv.14038736.v2 ◽

2021 ◽

Author(s):

Florian Matz ◽

Arif Music ◽

Dorian Didier ◽

Thomas C. Jagau

Keyword(s):

Organic Synthesis ◽

Energy Barrier ◽

Density Functional ◽

Bond Formation ◽

Cross Coupling ◽

Coupled Cluster ◽

Coupling Reactions ◽

Cross Coupling Reactions ◽

Product Distributions ◽

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>

Download Full-text

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

International Journal for Innovation Education and Research ◽

10.31686/ijier.vol7.iss12.2098 ◽

2019 ◽

Vol 7 (12) ◽

pp. 492-498

Author(s):

ZeAndra Whitfield ◽

Janese Bibbs ◽

Ghislain R Mandouma ◽

John Miller ◽

Matt Bird ◽

...

Keyword(s):

Ion Pairs ◽

High Capacity ◽

Aqueous Electrolytes ◽

New Class ◽

Large Size ◽

Simple Filtration ◽

Battery Technology ◽

Work Supports ◽

And Storage ◽

Borate Salts

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.

Download Full-text