Chem. Asian J.

Chem. Asian J.

Probing Reaction Mechanism of [1,5]‐Migration in Pyrrolium and Pyrrole Derivatives: Activation of a Stronger Bond in Electropositive Groups Becomes Easier

The [1,5]‐migration reaction has attracted considerable attention from experimentalists and theoreticians for decades. Although it has been extensively investigated in various systems, studies on pyrrolium derivatives are underdeveloped. Herein, a theoretical study on the reaction mechanism of [1,5]‐migration in both pyrrolium and pyrrole derivatives is presented.

Aromaticity‐promoted C−F Bond Activation in Rhodium Complex: A Facile Tautomerization

Fluorine is the most electronegative element in the periodic table. Thus, activation of the carbon–fluorine (C−F) bond, the strongest single bond to carbon, has attracted considerable interest from both experimentalists and theoreticians. In comparison with numerous approaches to activate C−F bonds, the aromaticity‐promoted method is less developed. Herein, we demonstrate that the C−F bond activation could be achieved by a facile tautomerization, benefitting from aromaticity, which can stabilize both the transition states and products.

Rational Design of a Carbon–Boron Frustrated Lewis Pair for Metal‐free Dinitrogen Activation

Molecular nitrogen (N2) is abundant in the atmosphere and nitrogen, found in many biomolecules, is an essential element of life. The Haber–Bosch process, developed over 100 years ago, requires relatively harsh conditions to activate N2 on the iron surface and generate ammonia for use as fertilizer or to produce other chemicals, leading to consumption of more than 2% of the world’s annual energy supply. Thus, developing approaches for N2 activation under mild conditions is particularly important and urgent.

σ‐Aromaticity in a Fully Unsaturated Ring

Aromaticity is one of the most fundamental and fascinating chemical topics, attracting both experimental and theoretical chemists owing to its many manifestations. Both σ‐ and π‐aromaticity can be classified depending on the character of the cyclic electron delocalization. In general, σ‐aromaticity stabilizes fully saturated rings with σ‐electron delocalization whereas the traditional π‐aromaticity describes the π‐conjugation in fully unsaturated rings.

Probing the Most Aromatic and Antiaromatic Pyrrolium Rings by Maximizing Hyperconjugation and Push–Pull Effect

Hyperconjugation, a weak interaction in organic chemistry, can have a strong effect on aromaticity, leading to the concept of hyperconjugative aromaticity, which was first proposed by Mulliken in 1939. However, most studies are limited to main group chemistry. Here we report the most aromatic and antiaromatic pyrrolium ring by maximizing the hyperconjugation caused by transition metal fragments and the push–pull effect.

Probing a General Rule towards Thermodynamic Stabilities of Mono BN-doped Lower Polyenes

The BN-doped organic analogues are interesting as aliphatic amineboranes for hydrogen storage, precursors for aromatic borazines and adsorbent cage azaboranes. However, BN-doped aliphatic polyenes remained undeveloped. Herein, we perform theoretical calculations on two mono BN-doped aliphatic lower polyenes, 1,3-butadiene and 1,3,5-hexatriene. A general rule is proposed, i.e., isomers with terminal nitrogen and directly BN-connected, N−B(R), in particular, are of significant thermodynamic stability as compared with their inverse analogues (where boron is at the terminal position).

Triplet State Aromaticity: NICS Criterion, Hyperconjugation, and Charge Effects

Aromaticity, one of the most important concepts in organic chemistry, has attracted considerable interest from both experimentalists and theoreticians. It remains unclear which NICS index is best to evaluate the triplet-state aromaticity. Here, we carry out thorough density functional theory (DFT) calculations to examine this issue. Our results indicate that among the various computationally available NICS indices, NICS(1)zz is the best for the triplet state.

Unexpected 1,2-Migration in Metallasilabenzenes: Theoretical Evidence for Reluctance of Silicon to Participate in π Bonding

Density functional theory (DFT) calculations were carried out to investigate the 1,2-migration in metallasilabenzenes. The results suggested that the chloride migration of metallabenzenes is unfavorable due to the loss of aromaticity in the nonaromatic analogues. In sharp contrast, such a migration in metallasilabenzenes is favorable due to the reluctance of silicon to participate in π bonding. The migration of hydride and methyl group from the metal center to the silicon atom in metallasilabenzenes is computed to be also feasible.

Mechanistic Insight into the CO2 Capture by Amidophosphoranes: Interplay of the Ring Strain and the trans Influence Determines the Reactivity of the Frustrated Lewis Pairs

CO2 capture has attracted increasing attention owing to its contribution to global warming and climate change as a greenhouse gas. As an alternative strategy to transition-metal-based chemistry and catalysis, frustrated Lewis pairs have been developed to sequester CO2 efficiently under mild conditions. However, the mechanism of CO2 sequestration with amidophosphoranes remains unclear. Herein, we present a thorough density functional theory study on a series of amidophosphoranes.

Mechanistic Insight into the Nickel-Catalyzed Cross-Coupling of Aryl Phosphates with Arylboronic Acids: Potassium Phosphate is Not a Spectator Base but is Involved in the Transmetalation Step in the Suzuki–Miyaura Reaction

Spectator or actor? Density functional theory calculations were performed to examine the role of the base in the nickel-catalyzed cross-coupling of aryl phosphates with arylboronic acids. Potassium phosphate was found to not act as a spectator base but was involved in the transmetalation step, as shown by a lower barrier than that of a base-free process, owing to the activation of the carbonboron bond by the base. Further experimental observations support the theoretical findings.