Strong Coupling to Circularly Polarized Photons: Toward Cavity-Induced Enantioselectivity

The development of new methodologies for the selective synthesis of individual enantiomers is still one of the major challenges in synthetic chemistry. Many biomolecules, and also many pharmaceutical compounds, are indeed chiral. While the use of chiral reactants or catalysts has led to substantial progress in the field of asymmetric synthesis, a systematic approach applicable to general reactions has still not been proposed. In this work, we demonstrate that strong coupling to circularly polarized fields can induce asymmetry in otherwise nonselective reactions. Specifically, we show that the field induces stereoselectivity in the early stages of chemical reactions by selecting an energetically preferred direction of approach for the reagents. Although the effects observed thus far are too small to significantly drive asymmetric synthesis, our results provide a proof of principle for field-induced stereoselective mechanisms. These findings lay the groundwork for future research.

Integrating chemistry knowledge in large language models via prompt engineering

This paper presents a study on the integration of domain-specific knowledge in prompt engineering to enhance the performance of large language models (LLMs) in scientific domains. The proposed domain-knowledge embedded prompt engineering method outperforms traditional prompt engineering strategies on various metrics, including capability, accuracy, F1 score, and hallucination drop. The effectiveness of the method is demonstrated through case studies on complex materials including the MacMillan catalyst, paclitaxel, and lithium cobalt oxide. The results suggest that domain-knowledge prompts can guide LLMs to generate more accurate and relevant responses, highlighting the potential of LLMs as powerful tools for scientific discovery and innovation when equipped with domain-specific prompts. The study also discusses limitations and future directions for domain-specific prompt engineering development.

Supported-amine-catalyzed cascade synthesis of spiro-thiazolone-tetrahydrothiophenes: assessing HSA binding activity

We have devised a supported-amine-catalyzed efficient synthesis of spiro-thiazolone-tetrahydrothiophenes via a sulfa-Michael/aldol cascade approach. The catalyst demonstrated sustained efficacy over 21 cycles. These derivatives were found to exhibit excellent binding abilities with purified human serum albumin as indicated by both in silico and in vitro-based experiments.

Mixed-Linker Chiral 2D Covalent Organic Frameworks with Controlled Layer Stacking for Electrochemical Asymmetric Catalysis

Covalent organic frameworks (COFs) have undergone extensive research as heterogeneous catalysts for a wide range of significant reactions, but they have not yet been investigated in the realm of electrochemical asymmetric catalysis, despite their recognition as an economical and sustainable strategy for producing enantiopure compounds. Here, we report a mixed-linker strategy to design multicomponent two-dimensional (2D) chiral COFs with tunable layer stacking for highly enantioselective electrocatalysis. By crystallizing mixtures of triamines with and without the MacMillan imidazolidinone catalyst or aryl substituent (ethyl and isopropyl) and a dialdehyde derivative of thieno-[3,2-b]thiophene, we synthesized and structurally characterized a series of three-component homochiral 2D COFs featuring either AA or ABC stacking. The stacking modes that can be synthetically controlled through steric tuning using different aryl substituents affect their chemical stability and electrochemical performance. With the MacMillan catalyst periodically appended on their channels, all three COFs with conductive thiophene moieties can be highly enantioselective and recyclable electrocatalysts for the asymmetric α-arylation of aldehydes, affording alkylated anilines with up to 97% enantiomeric excess by an anodic oxidation/organocatalytic protocol. Presumably due to their higher charge transfer ability, the ABC stacking COFs exhibit improved reactivity compared to the AA stacking analogue. This work therefore advances COFs as electrocatalysts for asymmetric catalysis and may facilitate the design of more redox-active crystalline organic polymers for electrochemical enantioselective processes.

One-step assembly of a MacMillan catalyst-based phenolic-type polymer

We report herein a "bottom-up" approach for the one-step assembly of a MacMillan catalyst-based phenolic-type polymer (Mac-CP). The resulting self-supported polymeric organocatalyst possesses homogeneously distributed and highly concentrated catalytic sites. Furthermore, Mac-CP is soluble in CH₃CN but insoluble in hexane. This unique property can be used to employ the polymer as an efficient catalyst in homogeneous organocatalysis and heterogeneous recycling. As a result, Mac-CP possesses comparable catalytic activity and enantioselectivity to its homogeneous counterpart in the asymmetric Diels-Alder reaction (95% yield, 93% enantiomeric excess (ee) for endo and 92% ee for exo).

Recent Advances in Asymmetric Synthesis of Pyrrolidine-Based Organocatalysts and Their Application: A 15-Year Update

In 1971, chemists from Hoffmann-La Roche and Schering AG independently discovered a new asymmetric intramolecular aldol reaction catalyzed by the natural amino acid proline, a transformation now known as the Hajos-Parrish-Eder-Sauer-Wiechert reaction. These remarkable results remained forgotten until List and Barbas reported in 2000 that L-proline was also able to catalyze intermolecular aldol reactions with non-negligible enantioselectivities. In the same year, MacMillan reported on asymmetric Diels-Alder cycloadditions which were efficiently catalyzed by imidazolidinones deriving from natural amino acids. These two seminal reports marked the birth of modern asymmetric organocatalysis. A further important breakthrough in this field happened in 2005, when Jørgensen and Hayashi independently proposed the use of diarylprolinol silyl ethers for the asymmetric functionalization of aldehydes. During the last 20 years, asymmetric organocatalysis has emerged as a very powerful tool for the facile construction of complex molecular architectures. Along the way, a deeper knowledge of organocatalytic reaction mechanisms has been acquired, allowing for the fine-tuning of the structures of privileged catalysts or proposing completely new molecular entities that are able to efficiently catalyze these transformations. This review highlights the most recent advances in the asymmetric synthesis of organocatalysts deriving from or related to proline, starting from 2008.

Organocatalytic Polymers from Affordable and Readily Available Building Blocks for the Cycloaddition of CO2 to Epoxides

The catalytic cycloaddition of CO₂ to epoxides to afford cyclic carbonates as useful monomers, intermediates, solvents, and additives is a continuously growing field of investigation as a way to carry out the atom-economic conversion of CO₂ to value-added products. Metal-free organocatalytic compounds are attractive systems among various catalysts for such transformations because they are inexpensive, nontoxic, and readily available. Herein, we highlight and discuss key advances in the development of polymer-based organocatalytic materials that match these requirements of affordability and availability by considering their synthetic routes, the monomers, and the supports employed. The discussion is organized according to the number (monofunctional versus bifunctional materials) and type of catalytically active moieties, including both halide-based and halide-free systems. Two general synthetic approaches are identified based on the postsynthetic functionalization of polymeric supports or the copolymerization of monomers bearing catalytically active moieties. After a review of the material syntheses and catalytic activities, the chemical and structural features affecting catalytic performance are discussed. Based on such analysis, some strategies for the future design of affordable and readily available polymer-based organocatalysts with enhanced catalytic activity under mild conditions are considered.

Investigation of the Organocatalytic Chlorination of 2-Phenylpropanal

Results of an examination of the organocatalytic enantioselective α-chlorination of 2-phenylpropanal are described. Synthetic investigation including the screening of primary and secondary aminocatalysts, many different reaction conditions, and other α-branched aldehydes show that especially primary aminocatalysts can catalyze the formation of the α-chloro branched aldehydes in good yields, but only with moderate enantioselectivities. In order to try to understand the challenge in obtaining high enantioselectivity for the aminocatalytic α-chlorination of α-branched aldehydes a series of experimental investigations were performed employing 2-phenylpropanal as a model system. These investigations have been coupled with computational investigations, which provided important insight into the moderate enantioselectivity of this chlorination reaction. Analysis of the reaction showed, that the lack of control over the selectivity of formation of the (E)- and (Z)-enamine intermediate, and the clustering of reaction barriers of possible reaction pathways help to rationalize difficulties in producing high enantioselectivity.

DABCO-based chiral ionic liquids as recoverable and reusable organocatalyst for asymmetric Diels-Alder reaction

New DABCO-based chiral ionic liquids were synthesized and evaluated in asymmetric Diels-Alder reaction of cyclopentadiene with α,β-unsaturated aldehydes or 4-phenyl-3-buten-2-one. Chiral ionic liquid of modified MacMillan catalyst having a DABCO cation and hexafluorophosphate anion acts as organocatalyst (5 mol%) for the Diels-Alder reaction of crotonaldehyde and cyclopentadiene producing 98% of the product and 87% ee (endo) in CH₃ CN/H₂ O (95/5) at 25°C in 2 h. The scope and limitations of the catalysis were also studied by using cyclopentadiene and α,β-unsaturated aldehydes, and the Diels-Alder products were obtained in 18%-92% yields with 68%-93% ee. The catalyst was recycled and reused up to 6 cycles with a slight drop in ee and conversion of the product.

SuFEx-Click Approach for the Synthesis of Soluble Polymer-Bound MacMillan Catalysts for the Asymmetric Diels–Alder Reaction

Novel polymeric MacMillan catalysts were prepared from modified chiral imidazolidin-4-one monomers via sulfur(VI) fluoride exchange chemistry. The resulting polysulfates containing chiral imidazolidin-4-one units could be employed as polymeric organocatalysts for the asymmetric Diels–Alder reaction. With the use of these polysulfate catalysts, sufficient catalytic activity and enantioselectivity were obtained, which were similar to those obtained by monomeric catalysts in a homogeneous catalytic reaction. In addition, the polysulfate catalysts could be recovered and reused five times without a considerable loss of activity and selectivity.

Green Chemistry Meets Asymmetric Organocatalysis: A Critical Overview on Catalysts Synthesis

Can green chemistry be the right reading key to let organocatalyst design take a step forward towards sustainable catalysis? What if the intriguing chemistry promoted by more engineered organocatalysts was carried on by using renewable and naturally occurring molecular scaffolds, or at least synthetic catalysts more respectful towards the principles of green chemistry? Within the frame of these questions, this Review will tackle the most commonly occurring organic chiral catalysts from the perspective of their synthesis rather than their employment in chemical methodologies or processes. A classification of the catalyst scaffolds based on their E factor will be provided, and the global E factor (EG factor) will be proposed as a new green chemistry metric to consider, also, the synthetic route to the catalyst within a given organocatalytic process.

Straightforward Synthesis of Fluorinated Enals via Photocatalytic α-Perfluoroalkenylation of Aldehydes

(Per)fluorinated substances represent an important compound class with regard to drug design and material chemistry. We found a mild, operationally simple, and inexpensive photocatalytic perfluoroalkenylation reaction giving tetrasubstituted, highly electron-deficient enals straight from aldehydes. This one-step reaction tolerates various functional groups and can be applied to a wide range of substrates giving the products in yields of 52-84%.