Correction to "Iterative Dual-Metal and Energy Transfer Catalysis Enables Stereodivergence in Alkyne Difunctionalization: Carboboration as Case Study".

[This corrects the article DOI: 10.1021/acscatal.3c03570.].

Iterative Dual-Metal and Energy Transfer Catalysis Enables Stereodivergence in Alkyne Difunctionalization: Carboboration as Case Study.

Stereochemically defined tetrasubstituted olefins are widespread structural elements of organic molecules and key intermediates in organic synthesis. However, flexible methods enabling stereodivergent access to E and Z isomers of fully substituted alkenes from a common precursor represent a significant challenge and are actively sought after in catalysis, especially those amenable to complex multifunctional molecules. Herein, we demonstrate that iterative dual-metal and energy transfer catalysis constitutes a unique platform for achieving stereodivergence in the difunctionalization of internal alkynes. The utility of this approach is showcased by the stereodivergent synthesis of both stereoisomers of tetrasubstituted ß-boryl acrylates from internal alkynoates with excellent stereocontrol via sequential carboboration and photoisomerization. The reluctance of electron-deficient internal alkynes to undergo catalytic carboboration has been overcome through cooperative Cu/Pd-catalysis, whereas an Ir complex was identified as a versatile sensitizer that is able to photoisomerize the resulting sterically crowded alkenes. Mechanistic studies by means of quantum-chemical calculations, quenching experiments, and transient absorption spectroscopy have been applied to unveil the mechanism of both steps.

One-Metal/Two-Ligand for Dual Activation Tandem Catalysis: Photoinduced Cu-Catalyzed Anti-hydroboration of Alkynes.

A dual catalyst system based on ligand exchange of two diphosphine ligands possessing different properties in a copper complex has been devised to merge metal- and photocatalytic activation modes. This strategy has been applied to the formal anti-hydroboration of activated internal alkynes via a tandem sequence in which Cu/Xantphos catalyzes the B2pin2-syn-hydroboration of the alkyne whereas Cu/BINAP serves as a photocatalyst for visible light-mediated isomerization of the resulting alkenyl boronic ester. Photochemical studies by means of UV-vis absorption, steady-state and time-resolved fluorescence, and transient absorption spectroscopy have allowed characterizing the photoactive Cu/BINAP species in the isomerization reaction and its interaction with the intermediate syn-alkenyl boronic ester through energy transfer from the triplet excited state of the copper catalyst. In addition, mechanistic studies shed light into catalyst speciation and the interplay between the two catalytic cycles as critical success factors.

Beyond classical sulfone chemistry: metal- and photocatalytic approaches for C-S bond functionalization of sulfones.

The exceptional versatility of sulfones has been extensively exploited in organic synthesis across several decades. Since the first demonstration in 2005 that sulfones can participate in Pd-catalysed Suzuki-Miyaura type reactions, tremendous advances in catalytic desulfitative functionalizations have opened a new area of research with burgeoning activity in recent years. This emerging field is displaying sulfone derivatives as a new class of substrates enabling catalytic C-C and C-X bond construction. In this review, we will discuss new facets of sulfone reactivity toward further expanding the flexibility of C-S bonds, with an emphasis on key mechanistic features. The inherent challenges confronting the development of these strategies will be presented, along with the potential application of this chemistry for the synthesis of natural products. Taken together, this knowledge should stimulate impactful improvements on the use of sulfones in catalytic desulfitative C-C and C-X bond formation. A main goal of this article is to bring this technology to the mainstream catalysis practice and to serve as inspiration for new perspectives in catalytic transformations.

Interplay between the Directing Group and Multifunctional Acetate Ligand in Pd-Catalyzed anti-Acetoxylation of Unsymmetrical Dialkyl-Substituted Alkynes.

The cooperative action of the acetate ligand, the 2-pyridyl sulfonyl (SO2Py) directing group on the alkyne substrate, and the palladium catalyst has been shown to be crucial for controlling reactivity, regioselectivity, and stereoselectivity in the acetoxylation of unsymmetrical internal alkynes under mild reaction conditions. The corresponding alkenyl acetates were obtained in good yields with complete levels of ß-regioselectivity and anti-acetoxypalladation stereocontrol. Experimental and computational analyses provide insight into the reasons behind this delicate interplay between the ligand, directing group, and the metal in the reaction mechanism. In fact, these studies unveil the multiple important roles of the acetate ligand in the coordination sphere at the Pd center: (i) it brings the acetic acid reagent into close proximity to the metal to allow the simultaneous activation of the alkyne and the acetic acid, (ii) it serves as an inner-sphere base while enhancing the nucleophilicity of the acid, and (iii) it acts as an intramolecular acid to facilitate protodemetalation and regeneration of the catalyst. Further insight into the origin of the observed regiocontrol is provided by the mapping of potential energy profiles and distortion-interaction analysis.

anti-Hydroarylation of Activated Internal Alkynes: Merging Pd and Energy Transfer Catalysis.

A general catalytic anti-hydroarylation of electron-deficient internal alkynes compatible with both electron-poor and electron-rich aryl reagents is reported. This selectivity is achieved through a sequential syn-carbopalladation of the alkyne by an Ar-Pd species, followed by a tandem, Ir-photocatalyzed, counter-thermodynamic E → Z isomerization. The use of ortho-substituted boronic acids enables direct access to pharmaceutically relevant heterocyclic cores via a cascade process. Mechanistic insight into the involvement of Ar-Pd versus Pd-H as an active species is provided.

CuI-Catalyzed Asymmetric [3 + 2] Cycloaddition of Azomethine Ylides with Cyclobutenones.

The catalytic asymmetric 1,3-dipolar cycloaddition of cyclobutenones with azomethine ylides provides straightforward access to densely substituted 3-azabicyclo[3.2.0]heptanes. In the presence of CuI/(R)-Fesulphos as the catalytic system, high levels of diastereoselectivity and enantioselectivity were achieved (up to 98% enantiomeric excess (ee)).