Chemo-, regio- and stereoselective access to polysubstituted 1,3-dienes via Nickel-catalyzed four-component reactions.

1,2-Difunctionalization of alkynes offers a straightforward approach to access polysubstituted alkenes. However, simultaneous multi-component cascade transformations including difunctionalization of two alkynes with both syn- and anti-selectivity in one catalyst system is undeveloped and proves to be a significant challenge. Herein, we report a Nickel-catalyzed four-component reaction to access polysubstituted 1,3-dienes using two terminal alkynes, aryl boroxines, and perfluoroalkyl iodides, wherein the reaction forms three new C-C bonds in a single vessel and serve as a modular strategy to access polysubstituted 1,3-dienes with excellent chemoselectivity, good regioselectivity and exclusive stereoselectivity. Control experiments reveal the plausible reaction mechanism and DFT calculations explain the cause for the formation of this unusual four-component reaction. Furthermore, we successfully incorporate two biologically active units into 1,2,3,4-tetrasubstituted 1,3-dienes, which greatly increases the diversity of molecular scaffolds and brings more potential values to medicinal chemistry, the synthetic utility of our protocol is further demonstrated by the late-stage transformations.

Arylation of Terminal Alkynes: Transition-Metal-Free Sonogashira-Type Coupling for the Construction of C(sp)-C(sp2) Bonds.

Alkynes are attractive synthons for organic chemistry. Despite the prevalence of transition-metal-catalyzed Sonogashira reactions, a transition-metal-free version of the arylation of terminal alkynes is elusive. Herein, we report an efficient transition-metal-free Sonogashira-type coupling reaction for the one-pot arylation of alkynes to construct C(sp)-C(sp2) bonds from a tetracoordinate boron intermediate with NIS as a mediator. With its high efficiency, wide substrate range, and good functional group tolerance, this method is further supported by the gram-scale synthesis and subsequent modification of complex molecules.

Ruthenium/TiO2 -Catalyzed Hydrogenolysis of Polyethylene Terephthalate: Reaction Pathways Dominated by Coordination Environment.

Polyethylene terephthalate (PET) hydrogenolysis can produce benzene, toluene, and xylene (BTX), where the selectivity control is challenging. We report a reaction pathway dictated by the Ru coordination environment by examining the binding geometries of adsorbates on differently coordinated Ru centers and their evolution during PET hydrogenolysis. A BTX yield of 77 % was obtained using a Ru/TiO2 with a Ru coordination number of ca. 5.0 where edge/corner sites are dominant, while more gas and saturated products were formed for Ru/TiO2 containing primarily terrace sites. Density functional theory and isotopic labelling revealed that under-coordinated Ru edge sites favor "upright" adsorption of aromatic adsorbates while well-coordinated Ru sites favor "flat-lying" adsorption, where the former mitigates ring hydrogenation and opening. This study demonstrates that reaction pathways can be directed through controlled reactant/intermediate binding via tuning of the Ru coordination environment for efficient conversion of PET to BTX.

Enantioselective Copper-Catalyzed sp2/sp3 Diborylation of 1-Chloro-1-Trifluoromethylalkenes.

Fluorine-containing organoboron compounds have emerged as novel building blocks in chemical synthesis; among them, fluorinated sp2/sp3 diborylated compounds are particularly appealing, since they might undergo chemoselective and diversified transformations of different C-B bonds with fluorinated functionality, thus bringing versatility and complexity to the eventual products. However, expedient, synthetic strategies for the construction of such fluorinated diborylative compounds are very sparse. Herein, we disclose enantioselective Cu-catalyzed sp2/sp3 diborylations of 1-chloro-1-trifluoromethylalkenes, leading to diborylated compounds bearing a gem-difluoroalkenyl moiety; most intriguingly, the new formed C-B bonds include one stereoselective and optically pure Csp3-B bond. Further transformations on the eventual products demonstrated the values of our presented strategy.

Regioselective Cross-Coupling of Isatogens with Boronic Acids to Construct 2,2-Disubstituted Indolin-3-one Derivatives.

Herein we present a transition-metal-free cross-coupling reaction of isatogens with boronic acids through a 1,4-metalate shift of a boron "ate" complex. This coupling reaction provides a feasible method to deliver valuable 2,2-disubstituted indolin-3-one derivatives with excellent regioselectivity, which exhibit operational simplicity, good functional group tolerance, and a broad substrate scope.