Mechanistic Understanding of the Pd(0)-Catalyzed Coupling Cyclization of 1,2-Allenyl Ketones with Aryl Halides: A Computational Study

Palladium-Catalyzed Domino Heck/Cross-Coupling Cyclization Reaction: Diastereoselective Synthesis of Furan-Containing Indolines

Herein, a palladium-catalyzed diastereoselective dearomatization/cross-coupling cyclization reaction between N-arylacyl indoles and (E)-β-chlorovinyl ketones is reported. Through this cyclization/cycloisomerization cascade, a series of furan-containing indolines were obtained in yields up to 95%. The reaction features readily accessible starting materials, benzyl Pd(II)-catalyzed cycloisomerization of (E)-β-chlorovinyl ketones, the sequential formation of three bonds and bis-heterocycles, and excellent diastereoselectivity. More importantly, the carbene-secondary benzyl migratory insertion is proven to be a critical process in the sequential cyclizations.

Theoretical Insight into the Palladium-Catalyzed Prenylation and Geranylation of Oxindoles with Isoprene

This work presents a comprehensive mechanistic study of the ligand-controlled palladium-catalyzed prenylation (with C5 added) and geranylation (with C10 added) reactions of oxindole with isoprene. The calculated results indicate that the prenylation with the bis-phosphine ligand and geranylation with the monophosphine ligand fundamentally share a common mechanism. This mechanism involves the formation of two crucial species: a η3-allyl-Pd(II) cation and an oxindole carbon anion. Furthermore, the reactions necessitate the assistance of a second oxindole molecule, which serves as a Brønsted acid, providing a proton to generate the oxindole nitrogen anion. The oxindole nitrogen anion then acts as a Brønsted base, abstracting a C-H proton from another oxindole molecule to form an oxindole carbon anion. These mechanistic details differ significantly from those proposed in the experimental work. The present calculations do not support the presence of the Pd-H species and the η3, η3-diallyl-Pd(II) intermediate, which were previously suggested in experiments. The theoretical results rationalize the experimental finding that the bis-phosphine ligand favors the prenylation of oxindole, while the monophosphine ligand enables the geranylation of oxindole.

Modular Synthesis of Tetrasubstituted Pyrroles via an Annulative Migration Reaction of Allenyl Ketones and p-Toluenesulfonylmethyl Isocyanide

The metal-free cyclization of allenyl ketones and p-toluenesulfonylmethyl isocyanide (TosMIC), promoted by Cs₂CO₃, provides a convenient access to tetrasubstituted pyrroles in which an acyl group undergoes 1,2-migration. This tandem Michael addition/annulative migration synthetic strategy is general and high-yielding for various substituted allenyl ketones. Moreover, a phosphoryl or ester moiety is also a suitable functionality to enable such migration.

Palladium-Catalyzed Cyclizative Borylation of Allenyl Ketones through Carbene Boryl Migratory Insertion: Access to Densely Substituted Furyl Boronates

Herein the palladium-catalyzed cyclizative borylation of allenyl ketones with diboron compounds is reported which involves the carbene boryl migratory insertion as the key step. This reaction features mild conditions, good functional group tolerance and broad substrate scope. Thus, it represents an efficient methodology for the assembly of diverse tri-substituted furyl boronates. In addition, a series of transformations of the resultant multi-substituted furyl boronates were conducted to provide various densely substituted furan derivatives in good yields, further illustrating the potential synthetic utility of this methodology.

DFT calculations in solution systems: solvation energy, dispersion energy and entropy

DFT calculations of reaction mechanisms in solution have always been a hot topic, especially for transition-metal-catalyzed reactions. The calculation of solvation energy is performed using either the polarizable continuum model (PCM) or the universal solvation model SMD. The PCM calculation is very sensitive to the choice of atomic radii to form a cavity, where the self-consistent isodensity PCM (SCI-PCM) has been recognized as the best choice and our IDSCRF radii can provide a similar cavity. Moving from a gas-phase case to a solution case, dispersion energy and entropy should be carefully treated. The solvent-solute dispersion is also important in solution systems, and it should be calculated together with the solute dispersion. Only half of the solvent-solute dispersion energy from the PCM calculation belongs to the solute molecules to maintain a thermal equilibrium between a solute molecule and its cavity, similar to the treatment of electrostatic energy. Relative solute dispersion energy should also be shared equally with the newly formed cavity. The entropy change from a gas phase to a liquid phase is quite large, but the modern quantum chemistry programs can only calculate the gas-phase translational entropy based on the idea-gas equation. In this review, we will provide an operable method to calculate the solution translational entropy, which has been coded in our THERMO program.

Fe-based MOFs@Pd@COFs with spatial confinement effect and electron transfer synergy of highly dispersed Pd nanoparticles for Suzuki-Miyaura coupling reaction

Controlling the spatial confinement effect and highly dispersed Pd nanoparticles (NPs) can help to improve applicability in catalysis, energy conversion, and separation. However, the nonspatial confinement effect, agglomeration of Pd NPs of catalyst and harsh reaction conditions have become the urgent problems to be solved in Suzuki-Miyaura cross-coupling reaction. Herein, we report the first application of a new MOFs@COFs by using core with metal organic frameworks (MOFs) NH₂-MIL-101(Fe) and shell with covalent organic frameworks (COFs) for loading Pd NPs. The quickly formation of a transition state, the highly dispersed Pd NPs and the advancedly spatial confinement effect were achieved by coupling Fe base synergistic active components, electron-oriented anchoring with controlling pore scale, respectively. Most notably, as a proof-of-concept application, the high catalytic activity of NH₂-MIL-101(Fe)@Pd@COFs(3 + 3) in catalysis is elucidated for Suzuki-Miyaura coupling reaction by the broad scope of the reactants and the preeminent yields of the products, together with excellent stability and recoverability. With this strategy, the mechanism of Suzuki-Miyaura coupling reaction was verified by examining the catalytic activity. We hope that our approach can further facilitate the study of the design and use of functional MOFs@Pd@COFs materials.

Mechanism of a cobalt-catalyzed hydroarylation reaction and origin of stereoselectivity

In the present study, the mechanism of a cobalt-catalyzed hydroarylation reaction between N-pyridylindole and 1,6-enynes and the origin of its stereoselectivity have been systematically investigated using the DFT calculation method.

Theoretical insight into the origins of chemo- and diastereo-selectivity in the palladium-catalysed (3 + 2) cyclisation of 5-alkenyl thiazolones

The mechanism of the palladium-catalysed (3 + 2) cyclisation of 5-alkenyl thiazolones and VECs has been investigated from a computational perspective, and the origins of unique chemoselectivity and excellent diastereoselectivity have been disclosed.