Progress in Carbonylative-Heck Reactions of Aryl Bromides: Catalysis and DFT Studies

Palladium-Catalyzed Cyclization/Alkenylation of Ynone Oximes with Vinylsilanes for the Assembly of Isoxazolyl Vinylsilanes

A palladium-catalyzed cascade cyclization/alkenylation for the assembly of synthetically valuable isoxazolyl vinylsilane derivative has been accomplished. Easily accessible ynone oximes, and available vinylsilane agents were used as the reaction starting materials This protocol features broad substrate scope, good functional group tolerance, and good step- and atom-economy. Remarkably, this approach provides a new approach for the construction of structurally diverse isoxazolyl-containing vinylsilanes with high molecular complexity, showing a promising application in synthetic and pharmaceutical chemistry.

Direct Aroylation of Olefins through a Cobalt/Photoredox-Catalyzed Decarboxylative and Dehydrogenative Coupling with α-Oxo Acids

A photoredox/cobalt dual catalytic procedure has been developed that allows benzoylation of olefins. Here the photoredox catalyst effects the decarboxylation of α-ketoacids to form benzoyl radicals. After addition of this radical to styrenes, the cobalt catalyst abstracts a H-atom. Hydrogen evolution from the putative cobalt hydride intermediate allows a Heck-like aroylation without the need for a stoichiometric oxidant. Mechanistic studies reveal that electronically different styrenes lead to a curved Hammett plot, thus suggesting a change in product-determining step in the catalytic mechanism.

Computational determination of the mechanism of the Pd-catalyzed formation of isatoic anhydrides from o-haloanilines, CO, and CO2

The palladium-catalyzed annulation of o-haloanilines with carbon monoxide (CO) and carbon dioxide (CO₂), discovered by Wen-Zhen Zhang and co-workers, provides a convenient method to synthesize isatoic anhydrides. We explored the mechanism of this reaction, particularly the order of the reaction of CO and CO₂ and the effect of the base, using density functional theory (DFT) calculations (ωB97X-D and M06). It was found that the base-assisted N-H bond activation through a concerted metalation-deprotonation (CMD) mechanism is a requisite for carboxylation, and the carboxylation proceeds via the nucleophilic attack of the (Pd)NH nitrogen on CO₂. The results show that carbonylation occurs prior to carboxylation, because the facile and exergonic carbonylation greatly decreases the energies of the following intermediates and transition states. The mechanistic exploration of the alternative pathways (e.g., mono-carbonylation and carboxylation) and the comparison with the annulation mechanism of the o-iodobenzylamine substrate further demonstrate the perfect cooperation of CO and CO₂ in constructing an anhydride moiety for o-haloanilines.

Pd/Cu-Catalyzed amide-enabled selectivity-reversed borocarbonylation of unactivated alkenes

The addition reaction between CuBpin and alkenes to give a terminal boron substituted intermediate is usually fast and facile. In this communication, a selectivity-reversed procedure has been designed and established. This selectivity-reversed borocarbonylation reaction is enabled by a cooperative action between palladium and copper catalysts and proceeds with complete regioselectivity. The key to the success of this transformation is the coordination of the amide group and slower CuBpin formation by using KHCO₃ as the base. A wide range of β-boryl ketones were produced from terminal unactivated aliphatic alkenes and aryl iodides. Further synthetic transformations of the obtained β-boryl ketones have been developed as well.

A selectivity-reversed borocarbonylation reaction has been developed with complete regioselectivity.

Direct visible photoexcitation on palladium nanocatalysts by chemisorption with distinct size dependence

Direct photoexcitation of metal nanoparticles (NPs) can induce selective chemical reactions that are difficult to achieve with thermal energy.

Synthesis of α,β-unsaturated carbonyl compounds by carbonylation reactions

Carbonylation reactions represent one of the most important tool box for the synthesis of α,β-unsaturated carbonyl compounds which are key building blocks in organic chemistry. This paper summarizes the most important advances in this field.

Pd-catalyzed synthesis of α,β-unsaturated ketones by carbonylation of vinyl triflates and nonaflates

A general and highly chemoselective Pd-catalyzed protocol for the synthesis of α,β-unsaturated ketones by carbonylation of vinyl triflates and nonaflates is presented. Applying the specific monophosphine ligand cataCXium® A, the synthesis of various vinyl ketones as well as carbonylated natural product derivatives proceeds in good yields.

Palladium-catalyzed carbonylative Heck reaction of aryl bromides with vinyl ethers to 3-alkoxy alkenones and pyrazoles

Three COming together: The first carbonylative Heck coupling reaction of aryl bromides and vinyl ethers leading to 1-aryl-3-alkoxy-2-propen-1-ones has been established (see scheme). Based on this coupling methodology, a novel one-pot synthesis of aryl-substituted pyrazoles was also realized.