Catalytic Hydrofunctionalization Reactions of 1,3-Diynes

Palladium-catalyzed hydroarylation of 1,3-diynes with arylboronic acids

Transition-metal-catalyzed selective hydroarylation of alkynes represents a state-of-the-art approach in organic chemistry. Herein, we report the reaction of symmetrical 1,3-diynes and arylboronic acids, with Pd(OAc)2 as the catalyst and PCy3 as the ligand, affording functionalized enynes in good to excellent yields. Its efficiency is demonstrated by its good functional group tolerance and broad substrate scope. This method offers a general, convenient, and practical strategy for the modular synthesis of multisubstituted enynes. To comprehensively elucidate the mechanism of the Pd-based catalytic system in the hydroarylation of 1,3-diynes, we performed detailed DFT computations for the Pd-catalyzed hydroarylation reaction.

Accessing Z-Enynes via Cobalt-Catalyzed Propargylic Dehydrogenation

Alkenes constitute an enabling motif in organic synthesis, as they can be functionalized to form highly substituted molecules. Z-alkenes are generally challenging to access due to the thermodynamic preference for the formation of E-alkenes compared to Z-alkenes. Dehydrogenation methodologies to selectively form Z-alkenes have not yet been reported. Herein, we report a Z-selective, propargylic dehydrogenation that provides 1,3-enynes through the invention of a Co-catalyzed oxidation system. Observation of a kinetic isotope effect (KIE) revealed that deprotonation of the propargylic position is the rate limiting step. Additionally, isomerization experiments were conducted and confirmed that the observed Z-selectivity is a kinetic effect. A proposed stereomechanistic model for the Z-selectivity is included.

Unlocking Diverse π-Bond Enrichment Frameworks by the Synthesis and Conversion of Boronated Phenyldiethynylethylenes

The π-bond enrichment frameworks not only serve as a crucial building block in organic synthesis but also assume a pivotal role in the fields of materials science, biomedicine, photochemistry, and other related disciplines owing to their distinctive structural characteristics. The incorporation of various substituents into the C═C double bonds of tetrasubstituted alkenes is currently a highly significant research area. However, the synthesis of tetrasubstituted alkenes with diverse substituents on double bonds poses a significant challenge in achieving stereoselectivity. Here, we reported an efficient and convergent route of Cu-catalyzed borylalkynylation of both symmetrical and unsymmetrical 1,3-diynes, B2pin2, and acetylene bromide to the construction of boronated phenyldiethynylethylene (BPDEE) derivatives with excellent chemo-, stereo-, and regioselectivities. BPDEE derivatives could transform into novel tetrasubstituted organic π-conjugated gem-diphenyldiethynylethylene (DPDEE), vinylphenyldiethynylethylene (VPDEE), and phenyltriethynylethylene (PTEE) derivatives by a stepwise process, which provides a flexible platform for the synthesis of complex π-bond enrichment frameworks that were difficult to synthesize by previous methods. The initial optical characterization revealed that the synthesized molecules exhibited aggregation-induced emission (AIE) properties, which further establishes the groundwork for future applications and enriches and advances the field of functional π-conjugated frameworks research.

Synthesis, crystal structure, Hirshfeld surface analysis and DFT study of the 1,1'-(buta-1,3-diyne-1,4-di-yl)bis-(cyclo-hexan-1-ol)

The title compound, C16H22O2, was synthesized in order to obtain its guest-free form because 'wheel-and-axle'-shaped mol-ecules tend to crystallize from solutions as solvates or host-guest mol-ecules. It crystallizes in the monoclinic space group P2/c with two crystallographically non-equivalent mol-ecules, one situated on an inversion center and the other on a twofold axis. The rod-like 1,3-diyne fragments have the usual linear geometry. In the crystal, O-H ⋯ O bonds form eight-membered rings of the R 4 4(8) type, linking mol-ecules into layers. The Hirshfeld surface analysis indicates that the largest con-tributions are from inter-molecular H⋯H (ca 71%) and H⋯C/C⋯H (ca 19%) contacts. The energies of the frontier mol-ecular orbitals were determined by DFT calculations at the B3LYP/def2-TZVP level of theory.

10th Anniversary of Catalysts: Molecular Catalysis

On the occasion of this Special Issue, I would like to present an editorial message on this good occasion [...]