Yuya Hu

Gas‐glue CO₂ : CO₂ can act as a “gas glue” to cross‐link trefoil‐like frustrated Lewis molecular pairs into a new form of molecular network. The CO₂‐bridged cross‐links are dynamically covalent, which endows the gel network with unique gas‐modulated viscoelastic, mechanical, and self‐healing performance.

Abstract

The design of structurally dynamic molecular networks can offer strategies for fabricating stimuli‐responsive adaptive materials. Herein we first report a gas‐responsive dynamic gel system based on frustrated Lewis pair (FLP) chemistry. Two trefoil‐like molecules with bulky triphenylborane and triphenylphosphine groups are synthesized as complementary Lewis acid and base with trivalent sites. They can together bind CO₂ gas molecules and further form a cross‐linked network via the bonding interactions between FLPs and CO₂. Such CO₂‐bridged dative linkages are shown to be dynamic covalent bonds, which endow the frustrated Lewis network with adaptable behaviors and unprecedented gas‐regulated viscoelastic, mechanical, and self‐healing performance. This study is an initial attempt to apply the FLP concept in materials chemistry, but we believe that this strategy will open a promising future for gas‐sensitive smart materials.

A highly regioselective hydroalkenylation of imines or aldehydes with styrene derivatives was realized by dual catalysis with Ni(cod)₂/PCy₃ and either TsNH₂ or PhB(OH)₂. This process provides an atom‐, step‐, and redox‐economic pathway towards synthetically useful allylic amines and alcohols, and opens up a new avenue for the design of more versatile coupling reactions.

Quite labile P=P double bonds: Vinyl‐substituted diphosphenes featuring small HOMO–LUMO gaps undergo a facile P=P double bond cleavage, leading to a series of novel vinyl‐substituted phosphorus derivatives.

Abstract

The reactions of the cyclic alkyl amino carbene (CAAC) 1 with phosphaalkynes generate the kinetically unstable CAAC‐derived phosphirenes 4 and 5, which undergo rearrangement/dimerization reactions to give the vinyl‐substituted diphosphenes 2, 3, and 6. The P=P double bond scission of 2 or 3 is unprecedentedly effected by S₈, [AuCl(tht)], or MeOTf at room temperature, which affords a dithiophosphorane 7, a phosphepine Au complex 8, or phosphepinium cations 9 and 10, respectively. The cationic species feature little homoaromaticity while representing the first examples of the phosphorus‐containing analogue of the tropylium ion.

Consuming alcohol: A conventional Yamanoi‐type C(sp²)−Si cross‐coupling reaction turns into a C(sp³)−Si bond formation accompanied by formal alkene hydrogenation in the presence of alcohols or water. By this, dihydrosilanes are directly converted into silyl ethers of tertiary silanes. Even bulky alcohols participate in this reaction because of the intermediacy of a highly reactive silyl iodide.

Abstract

A one‐pot reaction that directly converts dihydrosilanes into silyl ethers of tertiary silanes is reported. Under palladium catalysis, one Si−H bond of the dihydrosilane formally engages in C(sp³)−Si bond formation with a vinyl iodide while the other Si−H bond is transformed into a silyl iodide that undergoes facile alcoholysis with an alcohol. The C−C double bond is reduced in that process. This three‐component reaction provides in a single synthetic operation an access to silyl ethers of functionalized and hindered alcohols. Several of those would otherwise be difficult to make but the intermediacy of a highly reactive silyl iodide even allows for tert‐butanol to react at room temperature.

Enantioselective α-functionalizations of ketones via allylic substitution of silyl enol ethers

Enantioselective α-functionalizations of ketones via allylic substitution of silyl enol ethers, Published online: 19 November 2018; doi:10.1038/s41557-018-0165-x

The road less travelled: Select pyridinium reagents undergo an unprecedented heterolytic fragmentation upon single electron reduction to afford a synthetically viable N‐pyridyl radical cation. This reactive species was leveraged for the C−H amination of (hetero)arenes to furnish N‐aryl pyridinium products, which enable access to diverse nitrogen scaffolds.

Abstract

Electron‐transfer photocatalysis provides access to the elusive and unprecedented N‐pyridyl radical cation from selected N‐substituted pyridinium reagents. The resulting C(sp²)−H functionalization of (hetero)arenes furnishes versatile intermediates for the development of valuable aminated aryl scaffolds. Mechanistic studies that include the first spectroscopic evidence of a spin‐trapped N‐pyridyl radical adduct implicate SET‐triggered, pseudo‐mesolytic cleavage of the N−X pyridinium reagents mediated by visible light.

A Pd‐catalyzed atroposelective C−H allylation with allylic surrogates is reported. tert‐Leucine was identified as an efficient catalytic transient chiral auxiliary. A range of enantioenriched biaryls were prepared in synthetically useful yields with enantioselectivity up to >99 % ee through β‐O elimination. The reaction could be scaled up and the products could be further converted into enantiomerically pure axially chiral carboxylic acids.

Abstract

Biaryl atropisomers are of great importance in natural products, pharmaceuticals, and asymmteric synthesis. The efficient synthesis of these chiral scaffolds with full enantiocontrol and high diversity remains challenging. Reported herein is a Pd‐catalyzed atroposelective C−H allylation with tert‐leucine as an efficient catalytic chiral transient auxiliary. A wide range of enantioenriched biaryl aldehydes were prepared in synthetically useful yields with excellent enantioselectivity (up to >99 % ee) through β‐O elimination. The reaction could be carried out on a gram scale without erosion of the ee value. A variety of axially chiral carboxylic acids could be obtained with high enantiopurity. The resulting axially chiral biaryl aldehydes and carboxylic acids might be used in asymmetric synthesis as chiral ligands and/or organocatalysts.

Despite the enormous potential for the use of stereospecific cross-coupling reactions to rationally manipulate the three-dimensional structure of organic molecules, the factors that control the transfer of stereochemistry in these reactions remain poorly understood. Here we report a mechanistic and synthetic investigation into the use of enantioenriched alkylboron nucleophiles in stereospecific Pd-catalyzed Suzuki cross-coupling reactions. By developing a suite of molecular descriptors of phosphine ligands, we could apply predictive statistical models to select or design distinct ligands that respectively promoted stereoinvertive and stereoretentive cross-coupling reactions. Stereodefined branched structures were thereby accessed through the predictable manipulation of absolute stereochemistry, and a general model for the mechanism of alkylboron transmetallation was proposed.

How to design a winning fellowship proposal

How to design a winning fellowship proposal, Published online: 06 November 2018; doi:10.1038/d41586-018-07297-x

Twenty things I wish I’d known when I started my PhD

Twenty things I wish I’d known when I started my PhD, Published online: 06 November 2018; doi:10.1038/d41586-018-07332-x

Catalytic activation of unstrained C(aryl)–C(aryl) bonds in 2,2′-biphenols

Catalytic activation of unstrained C(aryl)–C(aryl) bonds in 2,2′-biphenols, Published online: 05 November 2018; doi:10.1038/s41557-018-0157-x