Xu-Qiong Xiao

N-Heterocyclic carbenes (NHCs) have been widely utilized over the past three decades due to their broad applications, yet synthetic methods for their preparation remain limited. A promising approach for NHC generation involves the thermolysis of NHC adducts. Herein, we report the synthesis of NHC pentafluorobenzene adducts featuring an o-carboranyl group in the backbone (2), which, unlike previously studied systems, resists thermal decomposition. Density functional theory (DFT) calculations were used to investigate the discrepancy, revealing that the decomposition reaction is kinetically controlled. For widely studied NHC systems like IMes and SIMes, the activation barriers were calculated to be 246.3 kJ/mol and 267.3 kJ/mol, respectively, aligning with reactions requiring heating. In contrast, the o-carborane system exhibited a significantly higher barrier of 320.5 kJ/mol, primarily due to the structural influence of the o-carborane backbone. Further analysis indicates that delocalization of π-electrons from the backbone into the NHC’s p-orbitals lowers the activation barrier, whereas delocalization into an exo-NHC ring increases it. These findings provide new insights into the thermal generation of NHCs and we hope it can offer guidance for future NHC design and synthesis.

Nido-C₂B₉ carborane anion supported Zn–salen complexes are superior to closo-carborane supported ones in ROCOP of epoxides and anhydrides.

The self-assembly of metallo-supramolecules has attracted considerable attention in recent decades. These discrete architectures are primarily driven by coordination interactions, typically involving M-N/O (Werner-type) or M-C (organometallic) bonding. However, the use of M-π interactions for constructing these multinuclear complexes remains largely unexplored. In this work, we report the self-assembly of trinuclear and tetranuclear copper(I) complexes driven by a combination of M-π and M-C coordination interactions. These multinuclear Cu(I)-NHC complexes were synthesized from the nido-carborane-supported N-heterocyclic carbene (NHC) precursors and Cu(I) ions. In solution, a dynamic equilibrium between the trinuclear and tetranuclear species was observed, as confirmed by the variable-temperature NMR spectrum. Van't Hoff analysis revealed that the equilibrium is endothermic (ΔH_eq = 53.6 kJ mol^-1) and entropically driven (ΔS_eq = 158 J mol^-1 K^-1). The solid-state structures of both forms were elucidated through single-crystal XRD analysis. Density functional theory calculations showed that the Cu-C_NHC bonds in these complexes are relatively weak (∼100 kJ mol^-1, approximately one-third of the strength of typical Cu-C_NHC bonds). This is attributed to the strong Coulombic attraction between positively charged Cu(I) and negatively charged nido-carborane ligands (M-π interactions), which significantly reduces the bond strength between Cu(I) and neutral NHC moieties (M-C bonding).

A class of sulfonium ylide-based reagents for electrophilic deuteriodifluoromethylation is reported. Thus, a wide array of ubiquitous O-nucleophiles such as sulfonic acid, alcohol, carboxyl acid, and phosphoric acid are deuteriodifluoromethylated, providing a straightforward approach to access the OCF₂D-functionalizazed scaffolds that are otherwise challenging to synthesize using conventional methods. This base-free protocol also displays broad functional group compatibility and is amenable to effective late-stage modification of bioactive molecules.

An electrophilic trideuteromethylselenating reagent, Se -methyl- d ₃ benzenesulfonoselenoate has been developed for direct functionalization of a broad range of nucleophiles or electrophiles.

Because of the three-dimensional bioisosteric feature, bicyclo[1.1.1]pentylamines (BCPAs) are valuable scaffolds in synthetic chemistry and medicinal chemistry. Here, we report a Halogen Atom Transfer (XAT) mediated radical C-N coupling between C3-iodo-BCPs and diazonium salts in the presence of base. Similarly, a multicomponent reaction (MCR) enables the simultaneous construction of the C-C bond and C-N bond simultaneously. Versatile roles of diazonium salts were also explored.

The discovery of ferrocene in 1951 was a significant landmark in the field of organometallic chemistry, and since then, numerous sandwich- or half-sandwich metallic complexes have been reported. However, silver stands as an intriguing exception in this regard, and knowledge of its bonding situation has remained undisclosed. Herein, unprecedented 12-vertex metallacarboranes of Ag(I) (2a and 2b) were synthesized through the reaction of sodium hexamethyldisilazide (NaHMDS) with the mixture of nido-C₂B₉ carborane anion-supported N-heterocyclic carbene precursors (1a and 1b) and [Ag(PPh₃)Cl]₄. The X-ray structural analysis of the resulting metallacarboranes revealed a unique "slipped" half-sandwich structure, which is a rarity among cyclopentadienyl analogues. DFT calculations provided insights into the asymmetric π-interactions between the pentagonal C₂B₃ face and the silver ion.

A new, stable and scalable reagent based on a sulfoxide skeleton for direct deuteriodifluoromethylthiolation has been developed. The reagent displays excellent reactivities toward Tf₂O promoted C-H deuteriodifluoromethylthiolation of electron-rich arenes, indoles, alkenes, and intramolecular lactonization of 2-alkynylbenzoates. Moreover, high deuteration rates and good to excellent yields were achieved under metal-free reaction conditions. As a result, a wide range of deuteriodifluoromethylthilolated compounds were prepared, enabling further applications in drug discovery.

We report herein an unprecedented Cu(II)-catalyzed divergent synthesis of naphthofurans and benzochromanes from 2-naphthols, N,N-dimethylethanolamine, and methylene-3,4-dihydroquinazolin-2(1H)-ones (or methylene-3,4-dihydroquinazolin-2(1H)-thiones) under mild conditions. With methylene-3,4-dihydroquinazolin-2(1H)-ones, naphthofuran products were afforded through an unconventional [3 + 1 + 1] cyclization while benzochromanes were obtained via a routine [3 + 2 + 1] annulation when methylene-3,4-dihydroquinazolin-2(1H)-thiones were applied as substrates. Both products could be obtained via a one-pot/two-step process starting from 2-aminoacetophenone with isocyanates or isothiocyanates.