Dynamic crosslinking compatibilizes immiscible mixed plastics.

The global plastics problem is a trifecta, greatly affecting environment, energy and climate1-4. Many innovative closed/open-loop plastics recycling or upcycling strategies have been proposed or developed5-16, addressing various aspects of the issues underpinning the achievement of a circular economy17-19. In this context, reusing mixed-plastics waste presents a particular challenge with no current effective closed-loop solution20. This is because such mixed plastics, especially polar/apolar polymer mixtures, are typically incompatible and phase separate, leading to materials with substantially inferior properties. To address this key barrier, here we introduce a new compatibilization strategy that installs dynamic crosslinkers into several classes of binary, ternary and postconsumer immiscible polymer mixtures in situ. Our combined experimental and modelling studies show that specifically designed classes of dynamic crosslinker can reactivate mixed-plastics chains, represented here by apolar polyolefins and polar polyesters, by compatibilizing them via dynamic formation of graft multiblock copolymers. The resulting in-situ-generated dynamic thermosets exhibit intrinsic reprocessability and enhanced tensile strength and creep resistance relative to virgin plastics. This approach avoids the need for de/reconstruction and thus potentially provides an alternative, facile route towards the recovery of the endowed energy and materials value of individual plastics.

Enantioselective Synthesis of Cyclic Nitrones by Chemoselective Intramolecular Allylic Alkylation of Oximes.

The enantio- and chemoselective iridium-catalyzed N-allylation of oximes is described for the first time. Intramolecular kinetic resolution provides access to cyclic nitrones and enantioenriched aliphatic allylic alcohols. Salient features of this transformation are its ability to employ E/Z-isomeric mixtures of oxime starting materials convergently and high functional group tolerance. The implementation of N-allylation/1,3-dipolar cycloaddition reaction sequences furnishes tricyclic isoxazolidines in highly enantio- and diastereoselective fashion. The synthetic utility of the approach is demonstrated by the efficient, formal synthesis of the marine natural product (+)-halichlorine.

Iridium-Catalyzed Enantioselective Allylic Substitution with Aqueous Solutions of Nucleophiles.

The iridium-catalyzed asymmetric allylic substitution under biphasic conditions is reported. This approach allows the use of various unstable and/or volatile nucleophiles including hydrazines, methylamine, t-butyl hydroperoxide, N-hydroxylamine, α-chloroacetaldehyde and glutaraldehyde. This transformation provides rapid access to a broad range of products from simple starting materials in good yields and up to >99% ee and 20:1 d.r. Additionally, these products can be elaborated efficiently into a diverse set of cyclic and acyclic compounds, bearing up to four stereocenters.

Stereoselective Synthesis of Piperidines by Iridium-Catalyzed Cyclocondensation.

An iridium-catalyzed cyclocondensation of amino alcohols and aldehydes is reported. Intramolecular allylic substitution by an enamine intermediate and subsequent in situ reduction furnishes 3,4-disubstituted piperidines with high enantiospecificity and good diastereoselectivity. The modular approach and the broad functional group tolerance provide access to diverse piperidine derivatives, which were further functionalized to give a versatile set of products.

Stereodivergent Dual Catalytic α-Allylation of Protected α-Amino- and α-Hydroxyacetaldehydes.

Fully stereodivergent dual-catalytic α-allylation of protected α-amino- and α-hydroxyacetaldehydes is achieved through iridium- and amine-catalyzed substitution of racemic allylic alcohols with chiral enamines generated in situ. The operationally simple method furnishes useful aldehyde building blocks in good yields, more than 99% ee, and with d.r. values greater than 20:1 in some cases. Additionally, the γ,δ-unsaturated products can be further functionalized in a stereodivergent fashion with high selectivity and with preservation of stereochemical integrity at the Cα  position.

Total synthesis of (±)-hippolachnin†A.

The first total synthesis of the marine polyketide (±)-hippolachnin A has been achieved in nine linear steps and an overall yield of 9%. Rapid access to the oxacyclobutapentalene core structure was secured by strategic application of an ene cyclization.

Algorithm-Based Hearing and Speech Therapy Rehabilitation after Cochlear Implantation.

INTRODUCTION: Due to the changes in the indication range for cochlear implants and the demographic development towards an aging society, more and more people are in receipt of cochlear implants. An implantation requires a close-meshed audiological and logopedic aftercare. Hearing therapy rehabilitation currently requires great personnel effort and is time consuming. Hearing and speech therapy rehabilitation can be supported by digital hearing training programs. However, the apps currently on the market are to a limited degree personalized and structured. Increasing digitalization makes it possible, especially in times of pandemics, to decouple hearing therapy treatment from everyday clinical practice. MATERIAL AND METHODS: For this purpose, an app is in development that provides hearing therapy tailored to the patient. The individual factors that influence hearing outcome are considered. Using intelligent algorithms, the app determines the selection of exercises, the level of difficulty and the speed at which the difficulty is increased. RESULTS: The app works autonomously without being connected to local speech therapists. In addition, the app is able to analyze patient difficulties within the exercises and provides conclusions about the need for technical adjustments. CONCLUSIONS: The presented newly developed app represents a possibility to support, replace, expand and improve the classic outpatient hearing and speech therapy after CI implantation. The way the application works allows it to reach more people and provide a time- and cost-saving alternative to traditional therapy.

Enantio- and Chemoselective Intramolecular Iridium-Catalyzed O-Allylation of Oximes.

A method for the enantio- and chemoselective iridium-catalyzed O-allylation of oximes is described. Kinetic resolution in an intramolecular setting provides enantioenriched oxime ethers and aliphatic allylic alcohols. The synthetic potential of the products generated with this method is showcased by their elaboration into a series of heterocyclic compounds and the formal synthesis of glycoprotein GP IIb-IIIa receptor antagonist (-)-roxifiban. Preliminary mechanistic experiments and computational data shed light on the remarkable chemoselectivity of the reaction.

Enantioselective Iridium-Catalyzed α-Allylation with Aqueous Solutions of Acetaldehyde.

The enantioselective α-allylation of aqueous solutions of acetaldehyde using iridium- and amine-catalyzed substitution of racemic allylic alcohols is described. The method utilizes a readily available, safely handled aqueous solution of acetaldehyde and furnishes γ,δ-unsaturated aldehydes in good yields and greater than 99% enantiomeric excess. The synthetic potential of the method is demonstrated with the enantioselective formal syntheses of heliannuols C and E as well as heliespirones A and C.