Yuya Hu

Dual action: Asymmetric α‐alkylation of azlactones with nonconjugated alkenes is achieved through the dual catalytic action of Pd^II and a chiral phosphoric acid. The reaction enables expedient access to quaternary α‐amino‐acid products.

Abstract

A palladium(II)‐catalyzed enantioselective α‐alkylation of azlactones with nonconjugated alkenes is described. The reaction employs a chiral BINOL‐derived phosphoric acid as the source of stereoinduction, and a cleavable bidentate directing group appended to the alkene to control the regioselectivity and stabilize the nucleopalladated alkylpalladium(II) intermediate in the catalytic cycle. A wide range of azlactones were found to be compatible under the optimal reaction conditions to afford products bearing α,α‐disubstituted α‐amino‐acid derivatives with high yields and high enantioselectivity.

You will be upgraded: Isobutanol is a desirable gasoline alternative because of its compatibility with modern engine technology, high energy density, and high octane number. In this work, the first homogeneous non‐noble metal catalyst for sustainable production of isobutanol by upgrading of (bio)ethanol and widely available methanol is disclosed. The reaction proceeds at very low catalyst loading with a remarkable turnover number (9233) and up to 96 % isobutanol selectivity.

Abstract

Isobutanol serves as an ideal gasoline additive owing to its good compatibility with current engine technology, high energy density, and high octane number. Herein, an efficient and selective Mn‐catalyzed upgrading of ethanol with methanol into isobutanol is reported. This is the first example of deoxygenative coupling of lower alcohols to isobutanol by using a homogeneous non‐noble‐metal catalyst. This transformation proceeded at very low catalyst loading with a high turnover number (9233) and up to 96 % isobutanol selectivity.

In this work, we introduce a new class of luminescent, heterotrimetallic supramolecular constructs partnering two bis‐cyclometalated iridium centers with a diimine platinum acetylide center. Whereas most supramolecular constructs featuring cyclometalated iridium involve elaborate bridging ligands and are prepared under forcing conditions with low to moderate yields, the three Ir‐Pt‐Ir complexes described here are prepared at room temperature from simple precursors and isolated in near‐quantitative yields. ESI‐MS, NMR spectroscopy, and DOSY confirm the identity and homogeneity of the trimetallic products. In comparison with monometallic model complexes, analysis of UV‐vis absorption, steady‐state photoluminescence and time‐resolved emission reveals the impacts of supramolecular assembly on the photophysical properties. UV‐vis absorption and cyclic voltammetry suggest perturbation of some frontier orbital energies as a result of assembly, and the emission spectra and lifetimes reveal efficient excited‐state energy transfer via a Dexter mechanism, and show that the site of luminescence (platinum or iridium) depends on the identity of the cyclometalating ligand bound to iridium.

Farmers could teach scientists a trick or two for lobbying

Farmers could teach scientists a trick or two for lobbying, Published online: 05 February 2019; doi:10.1038/d41586-019-00487-1

Cooperation is key to success: Metal oxido moieties react with the sterically encumbered Lewis acid tris(pentafluoridophenyl)borane (see scheme) forming compounds with novel reactivity, covering a wide area in chemistry including small molecule activation, hydrogenation, hydrosilylation catalysis, and olefin metathesis. The redox property of the metal is used in a cooperative manner with the frustrated Lewis pair reactivity.

Abstract

Lewis acid–base pair chemistry has been placed on a new level with the discovery that adduct formation between an electron donor (Lewis base) and acceptor (Lewis acid) can be inhibited by the introduction of steric demand, thus preserving the reactivity of both Lewis centers, resulting in highly unusual chemistry. Some of these highly versatile frustrated Lewis pairs (FLP) are capable of splitting a variety of small molecules, such as dihydrogen, in a heterolytic and even catalytic manner. This is in sharp contrast to classical reactions where the inert substrate must be activated by a metal‐based catalyst. Very recently, research has emerged combining the two concepts, namely the formation of FLPs in which a metal compound represents the Lewis base, allowing for novel chemistry by using the heterolytic splitting power of both together with the redox reactivity of the metal. Such reactivity is not restricted to the metal center itself being a Lewis acid or base, also ancillary ligands can be used as part of the Lewis pair, still with the benefit of the redox‐active metal center nearby. This Minireview is designed to highlight the novel reactions arising from the combination of metal oxido transition‐metal or rare‐earth‐metal compounds with the Lewis acid B(C₆F₅)₃. It covers a wide area of chemistry including small molecule activation, hydrogenation and hydrosilylation catalysis, and olefin metathesis, substantiating the broad influence of the novel concept. Future goals of this young and exciting area are briefly discussed.

Cooperative action: The chemoselective activations of Morita–Baylis–Hillman carbonates from isatins and allylic carbonates are realized with Pd(PPh₃)₄, through generation of allylic phosphorus ylides and π‐allylpalladium complexes, respectively. After a cooperative catalytic γ‐regioselective allylic alkylation reaction, Heck coupling proceeds to give spirooxindoles, furnishing a [3+2] annulation reaction by an unprecedented auto‐tandem cooperative catalysis.

Abstract

Auto‐tandem catalysis (ATC), in which a single catalyst promotes two or more mechanistically different reactions in a cascade pattern, provides a powerful strategy to prepare complex products from simple starting materials. Reported here is an unprecedented auto‐tandem cooperative catalysis (ATCC) for Morita–Baylis–Hillman carbonates from isatins and allylic carbonates using a simple Pd(PPh₃)₄ precursor. Dissociated phosphine generates phosphorus ylides and the Pd leads to π‐allylpalladium complexes, and they undergo a γ‐regioselective allylic–allylic alkylation reaction. Importantly, a cascade intramolecular Heck‐type coupling proceeds to finally furnish spirooxindoles incorporating a 4‐methylene‐2‐cyclopentene motif. Experimental results indicate that both Pd and phosphine play crucial roles in the catalytic Heck reaction. In addition, the asymmetric versions with either a chiral phosphine or chiral auxiliary are explored, and moderate results are obtained.

Catalytic enantioselective construction of axial chirality in 1,3-disubstituted allenes

Catalytic enantioselective construction of axial chirality in 1,3-disubstituted allenes, Published online: 31 January 2019; doi:10.1038/s41467-018-07908-1

How to land a journal cover

How to land a journal cover, Published online: 31 January 2019; doi:10.1038/d41586-019-00349-w

An intermolecular asymmetric cascade dearomatization reaction of indole derivatives with propargyl carbonate was developed. The challenges of both the chemoselectivity between the carbon and nitrogen nucleophiles and the enantioselective control during the formation of an all‐carbon quaternary stereogenic center were well addressed by a Pd catalytic system derived from the Feringa ligand. A series of enantioenriched multiply substituted fused indolenines were provided in good yields with excellent enantioselectivity and chemoselectivity.

Abstract

An intermolecular asymmetric cascade dearomatization reaction of indole derivatives with propargyl carbonate was developed. The challenges associated with both the chemoselectivity between the carbon and nitrogen nucleophile and the enantioselective control during the formation of an all‐carbon quaternary stereogenic center were well addressed by a Pd catalytic system derived from the Feringa ligand. A series of enantioenriched multiply substituted fused indolenines were provided in good yields (71–86 %) with excellent enantioselectivity (91–96 % ee) and chemoselectivity (3/4>19:1 in most cases).

Flying squirrels are secretly pink

Flying squirrels are secretly pink, Published online: 28 January 2019; doi:10.1038/d41586-019-00307-6