Asymmetric synthesis of β-amino cyanoesters with contiguous tetrasubstituted carbon centers by halogen-bonding catalysis with chiral halonium salt

• Yasushi Yoshida,
• Maho Aono,
• Takashi Mino and
• Masami Sakamoto

Beilstein J. Org. Chem. 2025, 21, 547–555, doi:10.3762/bjoc.21.43

• product was obtained in moderate diastereo- and enantioselectivity, however, chloronium salt 9c did not show significant catalytic activity, and the product was formed in nearly the same yield as that obtained without a catalyst with low stereoselectivity. From these observations, bromonium salt 9a was

• found to be optimal in enantioselectivity, and iodonium salt 9b was superior in terms of diastereoselectivity. These results can be explained by the strength of halogen bonding: generally, iodo-substituted compounds form stronger halogen bonding with Lewis bases than chloro-substituted ones [1]. Notably

• amide moiety and with almost no enantioselectivity. Although the addition of a catalytic amount of 9e accelerated the reaction, the same diastereomer of 17b as the major product was obtained as for the reaction without a catalyst, which shows the importance of halonium salt moieties in our catalysts

Organocatalytic kinetic resolution of 1,5-dicarbonyl compounds through a retro-Michael reaction

• James Guevara-Pulido,
• Fernando González-Pérez,
• José M. Andrés and
• Rafael Pedrosa

Beilstein J. Org. Chem. 2025, 21, 473–482, doi:10.3762/bjoc.21.34

• its enantioselectivity, aliquots of the reaction mixture were taken at defined time intervals and analyzed by HPLC using a chiral column after passing them through a short silica gel pad. Some interesting conclusions can be made from the data in Table 1. Firstly, the retro-Michael reaction occurs, to

• , enantioselectivity increased until a specific time, and after that, the enantiomeric ratio decreased (compare entries 1–3 and 21–23 in Table 1). The interesting result is that the major enantiomer in the enantioenriched mixture is now the opposite of the one obtained when the ketone and the α,β-unsaturated aldehyde

• provide the highest enantiomeric ratio. The influence of catalyst, co-catalyst, and temperature on the reaction progress and enantioselectivity was further investigated. Different essays using 0.028 M toluene solutions were carried out, and the results are summarized in Table 2. The reaction also occurs

Beyond symmetric self-assembly and effective molarity: unlocking functional enzyme mimics with robust organic cages

• Keith G. Andrews

Beilstein J. Org. Chem. 2025, 21, 421–443, doi:10.3762/bjoc.21.30

• cyclodextrin) can promote enantioselectivity [76], although turnover from augmented macrocycles is not always achieved [26]. The affinity of generic hydrophobic pockets for a hydrophobic product often leads to product inhibition, since binding a single large product is entropically favored over binding two

Dioxazolones as electrophilic amide sources in copper-catalyzed and -mediated transformations

• Seungmin Lee,
• Minsuk Kim,
• Hyewon Han and
• Jongwoo Son

Beilstein J. Org. Chem. 2025, 21, 200–216, doi:10.3762/bjoc.21.12

• lactams in high yields and excellent enantioselectivities (2a, 2b, and 2d). It was observed that the steric environment affected both reactivity and enantioselectivity (2c). Six-membered lactams featuring propargylic (2e) and alkenyl (2f) motifs were also obtained with excellent regioselectivity and

• enantioselectivity. Furthermore, a lactam containing a quaternary carbon center (2g) was prepared. However, a lower enantioselectivity was observed for product 2h due to the similar steric environment of the two alkyl substituents. As shown in Figure 1, a catalytic cycle was proposed for the intramolecular C–H

• amide sources, were employed in this transformation. As shown in Scheme 8, several dioxazolones containing electron-rich substituents were transformed into the desired products with excellent enantioselectivity (23a and 23b). Otherwise, the electron-poor substituent-containing dioxazolones showed

Recent advances in electrochemical copper catalysis for modern organic synthesis

• Yemin Kim and
• Won Jun Jang

Beilstein J. Org. Chem. 2025, 21, 155–178, doi:10.3762/bjoc.21.9

• enantioselective C–H alkynylation of ferrocene carboxamides with terminal alkynes by using Cu/BINOL and an electrocatalytic system (Figure 5) [49]. 8-Aminoquinoline-assisted C–H functionalization provided planar chiral ferrocenes with high yield and enantioselectivity. This reaction can be applied to a wide range

• of substrates, including arylacetylenes with electron-donating and electron-withdrawing groups, and ferrocenyl amides with alkyl and acyl substituents on the other Cp ring. Additionally, the reaction showed similar reactivity and enantioselectivity on a 1 mmol scale. In 2020, Mei et al. reported the

• decreasing the oxidation potential. A range of functional groups, such as halides, ethers, and heterocycles, were tolerated well, yielding the corresponding enantioenriched products 14 with high enantioselectivity in the presence of chiral bisoxazoline ligand L2. A possible mechanism is depicted in Figure 5

Recent advances in organocatalytic atroposelective reactions

• Henrich Szabados and
• Radovan Šebesta

Beilstein J. Org. Chem. 2025, 21, 55–121, doi:10.3762/bjoc.21.6

• enantioselectivities. Compound 66d was incorporated into a thiourea organocatalyst framework and successfully tested in kinetic resolution with 73% enantioselectivity. The chiral phosphoric acid (CPA) (R)-C22 was used to catalyze the formation of a C–N chiral axis in the axially chiral product 68 from biarylamines 67

• enantioselectivity during the nucleophilic addition, and the subsequent aromatization completes central-to-axial chirality conversion delivering products 68. Dynamic kinetic resolution of naphthylindoles 69 was performed by reaction with bulky electrophiles such as azodicarboxylates 70 or o-hydroxybenzyl alcohols 72

• present on the amino group of the 1,3-benzenediamine, lower yields were reported, and substituting the amino group in position 3 for an N-methylamino or N,N-dimethylamino group led to a reduction in the enantioselectivity. Shao et al. developed the first organocatalyzed atroposelective Friedländer

Non-covalent organocatalyzed enantioselective cyclization reactions of α,β-unsaturated imines

• Sergio Torres-Oya and
• Mercedes Zurro

Beilstein J. Org. Chem. 2024, 20, 3221–3255, doi:10.3762/bjoc.20.268

• ]. Although quite important in all organocatalytic processes, there are specific organocatalysts which activate reactants through non-covalent interactions such as hydrogen bonding. These interactions are crucial to obtain high enantioselectivity in the reaction. The 1-azadienes possess an electronegative

• acid as additive and a mixture of toluene and water provided the best results in terms of yield and enantioselectivity. A wide scope was explored, including electron-donating substituents and electron-withdrawing groups, as well as heterocycles, giving densely functionalized chiral azaspirocyclic

• further investigate the potential utility of this methodology, a gram scale experiment was conducted affording product 16f in a good yield and a slight decrease of the enantioselectivity. Additionally, a derivatization of product 16f by hydrogenation was carried out to yield the tricyclic piperidine 17

Hypervalent iodine-mediated intramolecular alkene halocyclisation

• Charu Bansal,
• Oliver Ruggles,
• Albert C. Rowett and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 3113–3133, doi:10.3762/bjoc.20.258

• from the styrenyl starting materials is stereoselective, giving the syn-diasteroisomer in high yields. A chiral iodoarene catalyst 16 was employed, along with a stoichiometric sacrificial oxidant, to give good to excellent levels of enantioselectivity. This elegant strategy led to a variety of β

• aminofluorination using BF3·Et2O with a chiral aryliodide 16 catalyst (Scheme 20) [44]. The study successfully obtained various chiral fluorinated oxazine products 38 with high enantioselectivity (up to >99% ee) and diastereoselectivity (up to >20:1 dr). Control experiments showed that using Py·9HF or Et3N·3HF as

• with KBr and NaOAc, a range of chiral 2,3,6-trisubstituted bromomethylmorpholines 73 were synthesised in excellent yields and diastereoselectivities that ranged from nothing to excellent depending on the substrate. The enantioselectivity of the reaction was not measured. The authors suggested a

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• % yield with a 93:7 ratio of the anti:syn aldol product (63a:63b) and no enantioselectivity at pH 6.7, whereas at pH 3.6 the catalyst was completely inactive (Table 4). Although the supramolecular system composed of a porphyrin macrocycle and a secondary amine organocatalyst operated through the

Enantioselective regiospecific addition of propargyltrichlorosilane to aldehydes catalyzed by biisoquinoline N,N’-dioxide

• Noble Brako,
• Sreerag Moorkkannur Narayanan,
• Amber Burns,
• Layla Auter,
• Valentino Cesiliano,
• Rajeev Prabhakar and
• Norito Takenaka

Beilstein J. Org. Chem. 2024, 20, 3069–3076, doi:10.3762/bjoc.20.255

• systematic catalyst structure–reactivity and selectivity relationship study. The observed catalyst structure–enantioselectivity relationship of the present allenylation reaction was found exactly opposite to that of the analogous allylation reaction. The method provided eleven α-allenic alcohols in 22–99

• catalyst is (i.e., less degree of conformational freedom for a bound substrate), the better is the enantioselectivity for analogous chlorosilane-mediated reactionss [47][48][49][51][54]. Therefore, we gradually narrowed the chiral pocket of catalysts from 3 to 4, 5 [53], and 6 [56][57]. To our surprise

• , the enantioselectivity consistently decreased as the chiral pocket became narrower while the reactivity remained the same. As such, we reduced the size of the substituents that craft the chiral pocket (7) and found that unsubstituted catalyst 8 was the most enantioselective. This observed catalyst

Copper-catalyzed yne-allylic substitutions: concept and recent developments

• Shuang Yang and
• Xinqiang Fang

Beilstein J. Org. Chem. 2024, 20, 2739–2775, doi:10.3762/bjoc.20.232

• nucleophiles (Scheme 1b). However, to achieve a highly selective yne-allylic substitution, a range of challenges must be addressed. First, how to achieve the regioselectivity under the coexistence of alkenyl and alkynyl units; second, how to realize the enantioselectivity control that is remote from the

• carried out without the presence of terminal alkyne, although no ee value was obtained. Therefore, they speculated that the direct substitution at the benzyl position is the key to causing the side reaction that affected the enantioselectivity. Recently, Zhu and Xu et al. [74] achieved the η-nucleophilic

• to be the determining step for the enantioselectivity, while the diastereoselectivity is mainly induced by the chiral alkylated naphthol intermediate in the second annulation step (Scheme 46). Xu et al. [80] realized asymmetric [4 + 1] cyclization of yne-allylic esters with pyrazolones. This

5th International Symposium on Synthesis and Catalysis (ISySyCat2023)

• Anthony J. Burke and
• Elisabete P. Carreiro

Beilstein J. Org. Chem. 2024, 20, 2704–2707, doi:10.3762/bjoc.20.227

• novel lipophilic cinchona squaramide organocatalyst. This organocatalyst was evaluated in a benchmark Michael addition of acetylacetone to trans-β-nitrostyrene, yielding the Michael adduct with high yield and enantioselectivity. The hydrophobic chain of the catalyst allowed the organocatalyst to be

• easily recovered by precipitation using polar solvents. This catalyst proved to be excellent for the preparation of (S)-baclofen on a gram scale, furnishing the main chiral intermediate in high yield and enantioselectivity. Furthermore, the catalyst was recycled over five cycles while maintaining its

• terazosin and prazosin were successfully synthesized. Oliveira Jr. et al. developed a new methodology for the asymmetric synthesis of β-aryl-γ-lactam derivatives with very good yield and enantioselectivity [16]. This was achieved through a palladium-catalyzed Heck–Matsuda desymmetrization of N-protected 2,5

Computational design for enantioselective CO₂ capture: asymmetric frustrated Lewis pairs in epoxide transformations

• Maxime Ferrer,
• Iñigo Iribarren,
• Tim Renningholtz,
• Ibon Alkorta and
• Cristina Trujillo

Beilstein J. Org. Chem. 2024, 20, 2668–2681, doi:10.3762/bjoc.20.224

• now yield the same product, it is necessary to recalculate the %ee, but this time using an effective rate constant keff (Equation 3). In doing so, a small increase in enantioselectivity is observed, with now a (R) enantiomeric excess of 96%ee. The designed catalyst enables the generation of an almost

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

Asymmetric organocatalytic synthesis of chiral homoallylic amines

• Nikolay S. Kondratyev and
• Andrei V. Malkov

Beilstein J. Org. Chem. 2024, 20, 2349–2377, doi:10.3762/bjoc.20.201

• enantioselectivities for both electron-rich and electron-poor N-benzoylarylimines, aliphatic N-benzoylimines, and bulkier N-carboxyalkylimines. However, less sterically hindered N-carboxyalkyl- and N-carbamoylimines showed a significant drop in both enantioselectivity and yield. The observed enantioselectivity was

• ,β-unsaturated imines 9. However, with ethynylimines 12, the enantioselectivity dropped to a modest level. In addition, the reaction with sterically hindered tertiary allylboronates, such as the chiral (R)-α-cyclohexyl-α-methyl-allylboronate required the use of catalytic amounts of zinc tert-butoxide

• (Scheme 6). The study explored a broad range of p-methoxyphenyl (PMP)imines derived from aryl, heteroaryl and alkyl aldehydes (including ethyl glyoxylate), demonstrating yields of 57–98% and high enantioselectivity of 90–98%. Screening of aldehyde and amine components indicated that the method is

Stereoselective mechanochemical synthesis of thiomalonate Michael adducts via iminium catalysis by chiral primary amines

• Michał Błauciak,
• Dominika Andrzejczyk,
• Błażej Dziuk and
• Rafał Kowalczyk

Beilstein J. Org. Chem. 2024, 20, 2313–2322, doi:10.3762/bjoc.20.198

• . Mild enolization of thioesters allows for the generation of Michael adducts with good yields and stereoselectivities. Reactions in a ball mill afford product formation with similar efficacy to solution-phase reactions but with slightly reduced enantioselectivity, yet they yield products in just one

• Discussion Based on our previous experiences with low-reactive Michael acceptors [29], initial attempts were carried out using bifunctional squaramides, derivatives of cinchona. However, up to 45% yield of the desired product was obtained with poor enantioselectivity (14%, Scheme 2). Considering the

• product with 93% ee after 24 h, while the bifunctional primary amine-thiourea catalysts (system B) required 4 days to provide an adduct with similar enantioselectivity. Prolonged reaction time is in general the innate nature of organocatalytic reactions employing iminium activation approaches. With the

Catalysing (organo-)catalysis: Trends in the application of machine learning to enantioselective organocatalysis

• Stefan P. Schmid,
• Leon Schlosser,
• Frank Glorius and
• Kjell Jorner

Beilstein J. Org. Chem. 2024, 20, 2280–2304, doi:10.3762/bjoc.20.196

• Drawing inspiration from linear free energy relationships, MLR models, pioneered by Norrby and co-workers [83] and later further developed by Sigman and co-workers [69][82], are commonly used for the prediction of enantioselectivity. In such models, the substrates, catalysts, and other relevant reaction

• is insufficient to represent steric substituent properties. Instead, the authors used Sterimol parameters [84] as steric descriptors (Figure 5), showing superior correlations towards the enantioselectivity for a multitude of organocatalytic reactions. Sterimol parameters are calculated from a given

• descriptors for the prediction of the enantioselectivity for several previously reported reactions, showing improved prediction performance compared to non-Boltzmann-weighted Sterimol parameters. Apart from considering parameters of the entire conformer ensemble, it has been shown that informative models can

Factors influencing the performance of organocatalysts immobilised on solid supports: A review

• Zsuzsanna Fehér,
• Dóra Richter,
• Gyula Dargó and
• József Kupai

Beilstein J. Org. Chem. 2024, 20, 2129–2142, doi:10.3762/bjoc.20.183

• spaces. The confinement of the heterogeneous version of cinchona amine and thiourea catalysts was reported, leading to improved enantioselectivity values in the Michael addition of nitromethane (5) to chalcone (6) through modification of the pore size of mesoporous silica 8 or 9 (Scheme 2) [63]. Thus

• , for cinchona thiourea, enantioselectivity not only increased with reduced pore size but even reached the level of the homogeneous catalyst when the support pore size was reduced to 6.3 nm. This resulted in obtaining the (R)-configured product 7 with 63% yield and 93% ee, as opposed to a 55% yield and

• , experiments were conducted. It was discovered that the nanoparticles themselves catalysed the formation of the racemic product in the absence of the thiourea catalyst. This finding elucidates the relatively poor enantioselectivity observed in reactions catalysed by the magnetic nanoparticle-supported

Chiral bifunctional sulfide-catalyzed enantioselective bromolactonizations of α- and β-substituted 5-hexenoic acids

• Sao Sumida,
• Ken Okuno,
• Taiki Mori,
• Yasuaki Furuya and
• Seiji Shirakawa

Beilstein J. Org. Chem. 2024, 20, 1794–1799, doi:10.3762/bjoc.20.158

• ; enantioselectivity; halogenation; lactones; organocatalysis; Introduction Catalytic asymmetric halolactonizations of alkenoic acids are powerful methods for the preparation of important chiral lactones in enantioenriched forms [1][2][3][4][5][6][7][8][9][10][11]. A wide variety of chiral catalysts have been applied

• bifunctional sulfide (S)-1a (10 mol %) bearing a hydroxy group. This reaction yielded the desired δ-valerolactone product 3a with good yield and enantioselectivity [83% yield, 86:14 enantiomeric ratio (er)]. We further tested the reaction of 2a with a hydroxy-protected sulfide catalyst (S)-4 under the same

• conditions to evaluate the importance of the bifunctional design of the hydroxy-type chiral sulfide catalyst (S)-1a. As expected, the use of the hydroxy-protected catalyst (S)-4 produced 3a with significantly lower enantioselectivity (51:49 er). This outcome clearly underscores the crucial role of the

Primary amine-catalyzed enantioselective 1,4-Michael addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones

• Pooja Goyal,
• Akhil K. Dubey,
• Raghunath Chowdhury and
• Amey Wadawale

Beilstein J. Org. Chem. 2024, 20, 1518–1526, doi:10.3762/bjoc.20.136

• File 1), the catalyst I imparted the highest enantioselectivity (74% ee) of the Michael product 3aa (Table 1, entry 1). Different solvents (see details in Supporting Information File 1) were screened for the test reaction using 15 mol % of catalyst I. Among them, CHCl3 turned out to be the optimal

• solvent, as the product 3aa was isolated in reproducible yield (77%) and enantioselectivity 74% ee (Table 1, entry 3). Next, we explored a variety of achiral and/or chiral Brønsted acids A1–6 as additives in order to increase the yield and the enantioselectivity of the reaction (Table 1, entries 4–9). A

• marked increase in both the yield and enantioselectivity of the product 3aa were observed. Among the screened Brønsted acids A1–6, the combination of 15 mol % of the catalyst I and 30 mol % of (±)-mandelic acid (A5) was found to be superior in terms of enantioselectivity (92% ee) of the product 3aa

Towards an asymmetric β-selective addition of azlactones to allenoates

• Behzad Nasiri,
• Ghaffar Pasdar,
• Paul Zebrowski,
• Katharina Röser,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1504–1509, doi:10.3762/bjoc.20.134

• the use of 3 equiv Cs2CO3 in toluene (0.05 M) at room temperature as the best-suited conditions (Table 1, entry 13), allowing for the synthesis of 5a in moderate yield (61%) and enantioselectivity (81:19 er). With optimized conditions for the synthesis of enantioenriched (−)-5a at hand, we next

• investigated the generality of this protocol. As outlined in Scheme 2, differently substituted allenoates were reasonably well tolerated (see products 5a–d), albeit some erosion in enantioselectivity was observed when using a tert-butyl ester containing allenoate (product 5d). Various α-arylmethyl-substituted

• steric bulk (5p) leads to a somewhat lower enantioselectivity, while the methoxy-substituent does not have a strong impact on the yield. It should, however, be stated that some of the methoxy-containing products, i.e., the α-alkyl-substituted 5j and 5k tend to undergo partial nucleophilic ring opening by

Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• enantioselective intramolecular Cannizzaro reaction of aryl and alkyl glyoxals 1a–h and alcohol 2 using trisoxazoline (TOX) ligand (4)/copper catalysts to furnish the requisite mandelic esters 3a–h in good yields (greater than 90%) and high enantioselectivity. This was observed in the wide substrate scope as

• enantioselectivity of the resultant product (Scheme 1). A one-pot oxidation–Cannizzaro reaction of aryl methyl ketones to mandelic acid derivatives was observed in the presences of ytterbium triflate as the catalyst. The intramolecular reaction sequence employed a SeO2/Yb(OTf)3 combination to affect the in-situ

• % enantioselectivity. They employed a double asymmetric induction with (+)/(−)-menthol (12), and CuX2 bis(oxazoline) catalyst where the corresponding chiral mandelate ester 13 was obtained in 81% yield and high selectivity (90% de) (Scheme 6). The proposed mechanism of the reaction is depicted below. Hong et al

Enantioselective synthesis of β-aryl-γ-lactam derivatives via Heck–Matsuda desymmetrization of N-protected 2,5-dihydro-1H-pyrroles

• Arnaldo G. de Oliveira Jr.,
• Martí F. Wang,
• Rafaela C. Carmona,
• Danilo M. Lustosa,
• Sergei A. Gorbatov and
• Carlos R. D. Correia

Beilstein J. Org. Chem. 2024, 20, 940–949, doi:10.3762/bjoc.20.84

• followed by a sequential Jones oxidation. The overall method displays a broad scope and good enantioselectivity, favoring the (R) enantiomer. The applicability of the protocol is highlighted by the efficient enantioselective syntheses of the selective phosphodiesterase-4-inhibitor rolipram and the

• temperature gave the NH-unprotected γ-lactam 5a and the drug (R)-rolipram 5b in 79% and 97% yields, respectively, with excellent enantioselectivity. Hydrolysis of γ-lactam 5a in 6 N HCl aqueous solution at 100 °C for 10 hours then led to the formation of (R)-baclofen hydrochloride (6) in 76% yield (Scheme 6

• ). The total yields were determined to be 49% for (R)-baclofen hydrochloride (6) and 61% (R)-rolipram (5b) from starting pyrrolidine 1d. Determination of the absolute stereochemistry of the Heck adducts/lactams and rationalization of the enantioselectivity The absolute stereochemistry of the products was

Evaluation of the enantioselectivity of new chiral ligands based on imidazolidin-4-one derivatives

• Jan Bartáček,
• Karel Chlumský,
• Jan Mrkvička,
• Lucie Paloušová,
• Miloš Sedlák and
• Pavel Drabina

Beilstein J. Org. Chem. 2024, 20, 684–691, doi:10.3762/bjoc.20.62

• based on derivatives of imidazolidin-4-one were synthesised and characterised. The catalytic activity and enantioselectivity of their corresponding copper(II) complexes were studied in asymmetric Henry reactions. It was found that the enantioselectivity of these catalysts is overall very high and

• enhanced economic efficiency, eco-friendly practices, and reduced waste. Catalysts with the highest enantioselectivity have been employed in the synthesis of essential chiral intermediates for drug production, such as amprenavir [12], rivaroxaban [13][14], linezolid [13] and salmeterol [7]. Therefore

• donor ability to pyridine. This change reduces the ring size within the ligand structure, potentially increasing the space available for coordinating reacting species, thereby possibly enhancing catalytic activity and enantioselectivity. We also aimed to assess the impact of alkyl groups at the 5

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• cooperative catalytic effect of the two Cr(III) units. Control experiments without K+, or in the presence of competitive crown ether presented a reduced conversion rate and enantioselectivity, proving the conformation change in the reactivity of the system. Anion responsive tweezers The main types of anion

• higher activity and enantioselectivity due to the preorganization of the Cr(III) catalytic centers enabling bimetallic catalysis compared to the more flexible arrangement of the salen in the open form. The tweezers could be opened by breaking the thioether–rhodium bond with a combination of Cl− and CO