Sebastian Beil

Going for a spin: A rotary‐evaporation‐induced enantioselective aggregation of achiral phthalocyanines is reported. The chiral induction mechanisms are proposed, pioneering a novel scientific field in terms of linking macroscopic mechanical rotations to nanoscale molecular chirality.

Abstract

Fluid dynamics, resulting from the macroscopic mechanical rotation of either a rotary evaporator or a magnetic stirrer, has been shown to selectively induce one of two enantiomers (mirror‐image structures) in certain nanoscale supramolecules. As an alternative to giving a chiral twist to synthesized supramolecules or polymers, it is a challenge to reproducibly prepare chiral species by only using macroscopic mechanical rotations. Demonstrated here is a highly reproducible method for rotary‐evaporation‐induced enantioselective H‐aggregation of achiral phthalocyanines. Chiral induction mechanisms are proposed by using the chiroptical‐sign‐based absolute structures. These results will provide insight to the origin of the homochirality of life, and serves as a pioneering study in a novel scientific field in terms of admixing nanoscale molecular chemistry and macroscopic fluid dynamics.

Nature Communications, Published online: 04 December 2019; doi:10.1038/s41467-019-13381-1

An activating‐group‐assisted oxidative cross‐coupling strategy for the assembly of biaryl‐bridged cyclic peptides from natural amino acids was developed for the synthesis of arylomycin/G0775 and RP 66453 cyclic cores.

Abstract

Biaryl‐bridged cyclic peptides comprise an intriguing class of structurally diverse natural products with significant biological activity. Especially noteworthy are the antibiotics arylomycin and its synthetic analogue G0775, which exhibits potent activity against Gram‐negative bacteria. Herein, we present a simple, flexible, and reliable strategy based on activating‐group‐assisted catalytic oxidative coupling for assembling biaryl‐bridged cyclic peptides from natural amino acids. The synthetic approach was utilized for preparing a number of natural and unnatural biaryl‐bridged cyclic peptides, including arylomycin/G0775 and RP 66453 cyclic cores.

Diketopyrrolopyrrole (DPP) is one of the most promising building blocks for the construction of semiconductors for organic electronics. Inspired by their success in organic field‐effect transistors and organic solar cells, DPP‐based semiconductors have been introduced into more devices. The DPP‐based semiconductors used for a wide range of electronic devices are summarized.

Abstract

In recent times, fused aromatic diketopyrrolopyrrole (DPP)‐based functional semiconductors have attracted considerable attention in the developing field of organic electronics. Over the past few years, DPP‐based semiconductors have demonstrated remarkable improvements in the performance of both organic field‐effect transistor (OFET) and organic photovoltaic (OPV) devices due to the favorable features of the DPP unit, such as excellent planarity and better electron‐withdrawing ability. Driven by this success, DPP‐based materials are now being exploited in various other electronic devices including complementary circuits, memory devices, chemical sensors, photodetectors, perovskite solar cells, organic light‐emitting diodes, and more. Recent developments in the use of DPP‐based materials for a wide range of electronic devices are summarized, focusing on OFET, OPV, and newly developed devices with a discussion of device performance in terms of molecular engineering. Useful guidance for the design of future DPP‐based materials and the exploration of more advanced applications is provided.

Nature Nanotechnology, Published online: 09 December 2019; doi:10.1038/s41565-019-0577-9

Two birds, one stone: Oxime esters of aliphatic carboxylic acids were used as a bifunctional source of both C‐ and N‐radicals. The persistency of the N‐radicals enables highly selective intermolecular radical carboaminations of alkenes.

Abstract

An intermolecular, two‐component vicinal carboimination of alkenes has been accomplished by energy transfer catalysis. Oxime esters of alkyl carboxylic acids were used as bifunctional reagents to generate both alkyl and iminyl radicals. Subsequently, addition of the alkyl radical to an alkene generates a transient radical for selective radical–radical cross‐coupling with the persistent iminyl radical. Furthermore, this process provides direct access to aliphatic primary amines and α‐amino acids by simple hydrolysis.

An Sb₂Se₃‐nanowire‐based nanomotor shows strong dichroic response due to its highly anisotropic crystal structure. A polarotactic artificial microswimmer is realized by cross‐assembling two Sb₂Se₃ nanomotors, and can be navigated by controlling the polarization direction of the light.

Abstract

Light‐driven micro/nanomotors are promising candidates for long‐envisioned next‐generation nanorobotics for targeted drug delivery, noninvasive surgery, nanofabrication, and beyond. To achieve these fantastic applications, effective control of the micro/nanomotor is essential. Light has been proved as the most versatile method for microswimmer manipulation, while the light propagation direction, intensity, and wavelength have been explored as controlling signals for light‐responsive nanomotors. Here, the controlling method is expanded to the polarization state of the light, and a nanomotor with a significant dichroic ratio is demonstrated. Due to the anisotropic crystal structure, light polarized parallel to the Sb₂Se₃ nanowires is preferentially absorbed. The core–shell Sb₂Se₃/ZnO nanomotor exhibits strong dichroic swimming behavior: the swimming speed is ≈3 times faster when illuminated with parallel polarized light than perpendicular polarized light. Furthermore, by incorporating two cross‐aligned dichroic nanomotors, a polarotactic artificial microswimmer is achieved, which can be navigated by controlling the polarization direction of the incident light. Compared to the well‐studied light‐driven rotary motors based on optical tweezers, this dichroic microswimmer offers eight orders of magnitude light‐intensity reduction, which may enable large‐scale nanomanipulation as well as other heat‐sensitive applications.

Bolstering of optoelectronics and quantum optics with molecular–nanotube hybrids is highlighted. These systems reveal new fundamental issues related to confinement of molecules and excitons. Furthermore, they provide building blocks for efficient emission down to the single‐photon regime.

Abstract

Optoelectronics benefits from outstanding new nanomaterials that provide emission and detection in the visible and near‐infrared range, photoswitches, two level systems for single photon emission, etc. Among these, carbon nanotubes are envisioned as game changers despite difficult handling and control over chirality burdening their use. However, recent breakthroughs on hybrid carbon nanotubes have established nanotubes as pioneers for a new family of building blocks for optics and quantum optics. Functionalization of carbon nanotubes with molecules or polymers not only preserves the nanotube properties from the environment, but also promotes new performance abilities to the resulting hybrids. Photoluminescence and Raman signals are enhanced in the hybrids, which questions the nature of the electronic coupling between nanotube and molecules. Furthermore, coupling to optical cavities dramatically enhances single photon emission, which operates up to room temperature. This new light on nanotube hybrids shows their potential to push optoelectronics a step forward.

Two become one: A peptide‐catalyzed approach for the atroposelective coupling of naphthols and ester‐bearing quinones to access non‐C ₂‐symmetric BINOL‐type scaffolds is presented. The reaction gives good yields and enantioselectivity, and a diastereoselective functionalization of a naproxen analogue highlights the utility of this system.

Abstract

We have demonstrated that small, modular, tetrameric peptides featuring the Lewis‐basic residue β‐dimethylaminoalanine (Dmaa) are capable of atroposelectively coupling naphthols and ester‐bearing quinones to yield non‐C₂ ‐symmetric BINOL‐type scaffolds with good yields and enantioselectivity. The study culminates in the asymmetric synthesis of backbone‐substituted scaffolds similar to 3,3′‐disubstituted BINOLs, such as (R)‐TRIP, with good (94:6 e.r.) to excellent (>99.9:0.1 e.r.) enantioselectivity after recrystallization, and a diastereoselective net arylation of the minimally modified nonsteroidal anti‐inflammatory drug (NSAID) naproxen.

Heterobifunctional rotaxanes, featuring an amine‐based thread and a macrocyclic chiral 1,1′‐binaphthyl‐phosphoric acid, serve as efficient organocatalysts for the stereoselective addition of malonates to Michael acceptors. High‐level DFT calculations provided mechanistic insights and enabled rational catalyst improvements, leading to interlocked catalysts that surpass their non‐interlocked counterparts in terms of reaction rates and stereoselectivities.

Abstract

Heterobifunctional rotaxanes serve as efficient catalysts for the addition of malonates to Michael acceptors. We report a series of four different heterobifunctional rotaxanes, featuring an amine‐based thread and a chiral 1,1′‐binaphthyl‐phosphoric‐acid‐based macrocycle. High‐level DFT calculations provided mechanistic insights and enabled rational catalyst improvements, leading to interlocked catalysts that surpass their non‐interlocked counterparts in terms of reaction rates and stereoselectivities.

From patient to flask: Temozolomide (the standard of care for glioblastoma) and other imidazotetrazine compounds are repurposed into synthetic reagents. The prodrugs release alkyl diazonium species under aqueous conditions and were thus employed to conduct the two most widely used reactions of diazomethane, esterifications and cyclopropanations.

Abstract

Diazomethane is one of the most versatile reagents in organic synthesis, but its utility is limited by its hazardous nature. Although alternative methods exist to perform the unique chemistry of diazomethane, these suffer from diminished reactivity and/or correspondingly harsher conditions. Herein, we describe the repurposing of imidazotetrazines (such as temozolomide, TMZ, the standard of care for glioblastoma) for use as synthetic precursors of alkyl diazonium reagents. TMZ was employed to conduct esterifications and metal‐catalyzed cyclopropanations, and results show that methyl ester formation from a wide variety of substrates is especially efficient and operationally simple. TMZ is a commercially available solid that is non‐explosive and non‐toxic, and should find broad utility as a replacement for diazomethane.

Nature, Published online: 27 November 2019; doi:10.1038/s41586-019-1760-8

A Type I porous liquid is synthesized by transforming porous organic cages into porous ionic liquids via a supramolecular complexation strategy. Simple physical mixing of 18‐crown‐6 with an anionic porous organic cage affords a porous ionic liquid with anionic porous organic cages as the anionic parts and 18‐crown‐6/potassium ion complexes as the cationic parts.

Abstract

Porous liquids are a type of porous materials that engineer permanent porosity into unique flowing liquids, exhibiting promising functionalities for a variety of applications. Here a Type I porous liquid is synthesized by transforming porous organic cages into porous ionic liquids via a supramolecular complexation strategy. Simple physical mixing of 18‐crown‐6 with task‐specific anionic porous organic cages affords a porous ionic liquid with anionic porous organic cages as the anionic parts and 18‐crown‐6/potassium ion complexes as the cationic parts. In contrast, mixing of 15‐crown‐5 and anionic porous organic cages in a 2:1 ratio gives only solids, while the addition of excess 15‐crown‐5 affords a Type II porous liquid. The permanent porosity in the cage‐based porous liquids has been also confirmed by molecular simulation, positron (e⁺) annihilation lifetime spectroscopy, and enhanced gas sorption capacity compared with pure crown ethers.

Corrosion free: Two methods for the synthesis of vinyl halides by iridium‐catalyzed transfer hydrohalogenation of unactivated alkynes are described. The use of 4‐chlorobutan‐2‐one or tert‐butyl halide as donors of hydrogen halides allows this transformation in the absence of corrosive reagents. This method leads to alkenyl halide compounds containing acid‐sensitive groups, such as tertiary alcohols, silyl ethers, and acetals.

Abstract

Described herein are two different methods for the synthesis of vinyl halides by a shuttle catalysis based iridium‐catalyzed transfer hydrohalogenation of unactivated alkynes. The use of 4‐chlorobutan‐2‐one or tert‐butyl halide as donors of hydrogen halides allows this transformation in the absence of corrosive reagents, such as hydrogen halides or acid chlorides, thus largely improving the functional‐group tolerance and safety profile of these reactions compared to the state‐of‐the‐art. This method has granted access to alkenyl halide compounds containing acid‐sensitive groups, such as tertiary alcohols, silyl ethers, and acetals. The synthetic value of those methodologies has been demonstrated by gram‐scale synthesis where low catalyst loading was achieved.

Eight new macrocycles with reactive functional handles were synthesized through metalloid‐assisted self‐assembly. “Design of experiments” was utilized to optimize reaction conditions for multiple systems to significantly increase the yield of a single, targeted macrocycle.

Abstract

Cyclophanes are a venerable class of macrocyclic and cage compounds that often contain unusual conformations, high strain, and unusual properties. However, synthesis of complex, functional derivatives remains difficult due to low functional group tolerance, high dilution, extreme reaction conditions, and sometimes low yields using traditional stepwise synthetic methods. “Design of experiments” (DOE) is a method employed for the optimization of reaction conditions, and we showcase this approach to generate a dramatic increase in the yield of specific targets from two different self‐assembling systems. These examples demonstrate that DOE provides an additional tool in tuning self‐assembling, dynamic covalent systems.

Driven by electricity, the dehydrogenative coupling reaction of phenols carrying electron‐withdrawing groups to give 2,2′‐biphenols or the corresponding polycyclic derivatives is facilitated for the first time. 1,1,1,3,3,3‐Hexafluoroisopropanol and a small amount of base in the electrolyte make additional supporting electrolyte superfluous. The electrolysis is scalable, can be conducted with very simple equipment, and is much more concise than previous conventional syntheses.

Abstract

We herein present a metal‐free, electrosynthetic method that enables the direct dehydrogenative coupling reactions of phenols carrying electron‐withdrawing groups for the first time. The reactions are easy to conduct and scalable, as they are carried out in undivided cells and obviate the necessity for additional supporting electrolyte. As such, this conversion is efficient, practical, and thereby environmentally friendly, as production of waste is minimized. The method features a broad substrate scope, and a variety of functional groups are tolerated, providing easy access to precursors for novel polydentate ligands and even heterocycles such as dibenzofurans.

Nature Catalysis, Published online: 14 November 2019; doi:10.1038/s41929-019-0379-3

Crystal Engineering Hydrogen bonding in supramolecular assemblies of weak π‐electron donors and acceptors can cause a strong charge transfer. Modifying the acceptor leads to different types of semiconductivity, as described by D. F. Perepichka et al. in their Research Article on https://doi.org/10.1002/anie.201910288page 17312 ff.

Nature Chemistry, Published online: 18 November 2019; doi:10.1038/s41557-019-0358-y