N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• aldehydes and hydrogen-bond activation of nitroalkenes. Keywords: asymmetric organocatalysis; hydrogen bond; Michael addition; pyrrolidine; thiourea; urea; Introduction Asymmetric organocatalysis became one of the strategic ways for the efficient synthesis of chiral compounds [1]. Bifunctional catalysis

• has proven to be a successful concept in asymmetric organocatalysis [2][3][4][5][6][7][8]. An amine unit with a hydrogen-bond donating skeleton is highly efficient from among various possible combinations of catalytic moieties within an organocatalyst. This idea has been inspired by proline catalysis

• -sulfinylurea as bifunctional organocatalyst [23]. The enantio- and diastereoselective addition of Meldrum’s acids to nitroalkenes via N-sulfinylurea catalysis gave products that were readily converted to pharmaceutically relevant compounds [24][25]. A sulfinylurea organocatalyst catalyzed a highly selective

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• organocatalysts in asymmetric aza-MR. Keywords: asymmetric aza-Michael reaction; covalent bonding catalysis; nitrogen heterocycles; non-covalent bonding catalysis; organocatalysis; Introduction The Michael reaction though discovered about 135 years ago [1][2] continues to attract attention of the chemists owing

• high enantioselectivities (up to 65–91%) [40]. Rajasekar et al. developed an efficient one-pot tandem rhodium(II)/chiral squaramide relay catalysis for the enantioselective construction of dihydro-β-carbolines 37 from the Michael reaction of suitably substituted indole derivatives 34 with N-sulfonyl

• enantioselectivity (47–98% ee). The observed results were rationalized with density functional theory calculations (Table 8) [42]. 1.3 Reactions catalyzed by chiral amines He and co-workers developed heterogeneous synergistic catalysis using chiral amines SBA-15 (cat. 44), which promote aza-Michael–Henry cascade

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• Yajing Zhang Qian Wang Zongsheng Yan Donglai Ma Yuguang Zheng Traditional Chinese Medicine Processing Technology Innovation Center of Hebei Province, Hebei University of Chinese Medicine, Shijiazhuang, 050200, P. R. China 10.3762/bjoc.17.169 Abstract Photoredox catalysis has been applied to

• widely investigated, because they are abundant and less expensive. This review discusses the scope and application of photoinduced copper-based catalysis along with recent progress in this field. The special features and mechanisms of copper photocatalysis and highlights of the applications of the copper

• ; mechanisms of copper photocatalysis; photoinduced copper-based catalysis; photoredox catalysis; special features of copper photocatalysis; Introduction Solar light is an inexhaustible and free energy source for green plants and bacteria. Photosynthetic organisms absorb solar energy and convert it into

Direct C(sp³)–H allylation of 2-alkylpyridines with Morita–Baylis–Hillman carbonates via a tandem nucleophilic substitution/aza-Cope rearrangement

• Siyu Wang,
• Lianyou Zheng,
• Shutao Wang,
• Shulin Ning,
• Zhuoqi Zhang and
• Jinbao Xiang

Beilstein J. Org. Chem. 2021, 17, 2505–2510, doi:10.3762/bjoc.17.167

• precursors have also been widely explored in the past decades. These reactions typically proceed under the catalysis of a nucleophilic tertiary amine or phosphine, and no metal catalysts are needed, which makes this strategy more synthetically useful for the construction of allyl-substituted scaffolds

Copper-catalyzed monoselective C–H amination of ferrocenes with alkylamines

• Zhen-Sheng Jia,
• Qiang Yue,
• Ya Li,
• Xue-Tao Xu,
• Kun Zhang and
• Bing-Feng Shi

Beilstein J. Org. Chem. 2021, 17, 2488–2495, doi:10.3762/bjoc.17.165

• Zhen-Sheng Jia Qiang Yue Ya Li Xue-Tao Xu Kun Zhang Bing-Feng Shi School of Biotechnology and Health Sciences, Wuyi University, Jiangmen, Guangdong, 529020, China Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang, 310027, China Green Catalysis Center and College of Chemistry

• the directing group could be removed easily under basic conditions. Keywords: amination; C–H activation; copper; ferrocene; mono-selectivity; Introduction Ferrocene-based compounds have broad applications from asymmetric catalysis to medicinal discovery [1][2][3][4][5][6][7][8]. Therefore, the

• in 2020, an enantioselective C–H annulation of ferrocenylformamides with alkynes was achieved by the Ye group enabled by Ni-Al bimetallic catalysis and a chiral secondary phosphine oxide (SPO) ligand [35]. Hou et al. also reported the asymmetric C−H alkenylation of quinoline- and pyridine-substituted

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• necessary for this transformation. Recently, copper hydride (CuH) catalysis has been a wonderful procedure for olefin hydrofunctionalization via the formation of nucleophilic alkylcopper intermediate. In 2016, Buchwald and co-workers described a CuH-catalyzed asymmetric addition of olefin to ketones [65

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• their HOMO/LUMO energy levels were estimated by cyclic voltammetry measurements. Besides, density functional theory calculations were carried out for further exploration of their electronic properties. Keywords: catalysis; cross-coupling; cyclization; fluorescence; palladium; Introduction π-Conjugated

Targeting active site residues and structural anchoring positions in terpene synthases

• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 2441–2449, doi:10.3762/bjoc.17.161

• residue (pyrophosphate sensor, located usually 46 residues upstream of the NSE triad, Figure 1) can be observed. Site-directed mutagenesis demonstrated that this residue is important for SdS catalysis [11]. Additional conserved residues include a Pro at the bottom of helix C causing a helix turn (21

• possible explanation may be that for efficient catalysis to yield a cyclic product the substrate needs to be tightly bound in the active site. If the space is too large, this may allow for too much conformational flexibility of the substrate which may prevent an efficient terpene cyclisation reaction. The

Enantioselective PCCP Brønsted acid-catalyzed aminalization of aldehydes

• Martin Kamlar,
• Robert Reiberger,
• Martin Nigríni,
• Ivana Císařová and
• Jan Veselý

Beilstein J. Org. Chem. 2021, 17, 2433–2440, doi:10.3762/bjoc.17.160

• chiral Brønsted acids. In the scope of Brønsted acid catalysis, chiral phosphoric acids (CPA) are dominating as potent catalysts in various asymmetric transformations [19][20][21][22][23], although the synthesis of these catalysts is expensive and laborious [24]. One of the most frequent examples of CPAs

• of aldehydes using PCCP catalysis. Our investigation commenced with the screening of the reaction between anthranilamide (1a) and isovaleraldehyde (2a) in the presence of 10 mol % of catalyst II (Table 1). First, we turned our attention to the solvent and temperature effect concerning the yield and

• strategies employing chiral Brønsted acid catalysis. X-ray single-crystal structure of aminal 3l with the displacement ellipsoids drawn at the 30% probability level. The substrate scope of the aminalization reaction for different aldehydes. aAfter recrystallization; breaction run at 1 mmol scale. The

A novel methodology for the efficient synthesis of 3-monohalooxindoles by acidolysis of 3-phosphate-substituted oxindoles with haloid acids

• Li Liu,
• Yue Li,
• Tiao Huang,
• Dulin Kong and
• Mingshu Wu

Beilstein J. Org. Chem. 2021, 17, 2321–2328, doi:10.3762/bjoc.17.150

• rearrangement under Brønsted base catalysis and the subsequent acidolysis with haloid acids. The mild reaction conditions, simple operation, good yield, and readily available and inexpensive starting materials make this protocol a valuable method for the preparation of various 3-halooxindoles on a large-scale

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• journal [22]. Attempts at reducing aryldiazonium salts organocatalytically have also been successful [23][24][25][26]. Inspired by the seminal work by Sanford [27], König et al. [28] designed a simple and effective CH-arylation reaction combining diazonium chemistry with photoredox catalysis. By using

• precursor, potentially leading to both regioisomers and unwanted side products, complicating purification. As a result, accounts of bis-arylation using radical chemistry are scarce and report very low yields [29][30][31][32]. While transition-metal catalysis is a viable strategy, it is often based on

Base-free enantioselective S_N2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis

• Mili Litvajova,
• Emiliano Sorrentino,
• Brendan Twamley and
• Stephen J. Connon

Beilstein J. Org. Chem. 2021, 17, 2287–2294, doi:10.3762/bjoc.17.146

• synthesis of a potent CRTH2 receptor antagonist. Keywords: alkylation; base-free; cinchona alkaloids; CRTH2 antagonist; hydrogen-bonding; oxindole; phase-transfer catalysis; Introduction The 2-oxindole scaffold is an important motif present in a myriad of natural products. Among 2-oxidole derivatives, 3,3

• this approach is significantly enhanced when both the substituents at the 3-position are modifiable as much as possible to facilitate further transformations. In this context, we realised that phase-transfer catalysis, due to its operational simplicity and utility in mediating reactions involving

• catalysis, have been reported [24][25][26][27][28][29][30]. However, despite the excellent levels of enantiocontrol often achieved, in the majority of these studies the 2-oxindole subjected to enantioselective alkylation lacks the structural architecture necessary for further modifications (Scheme 1A

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• development of the research area of asymmetric anion-binding organocatalysis. Key early elucidation studies with chloride as counter-anion confirmed this type of alternative activation, which was then exploited in several processes and contributed to the advance and consolidation of anion-binding catalysis as

• the cationic reactive species. Keywords: anion binding; asymmetric catalysis; halide anions; hydrogen donors; noncovalent interactions; Introduction Halogens and the respective anionic halides occupy an essential role in natural and chemical processes [1][2][3][4]. While in chemical syntheses

• receptors have often proven more efficient [9][12]. A breakthrough in the field of anion binding towards its application in catalysis was achieved with the findings that neutral (thio)urea derivatives are potent anion receptors due to their ability to bind anions of various topologies, including the

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• metallaphotoredox catalysis enabled C‒H functionalizations with unique reaction pathways under mild reaction conditions. Given the relative earth-abundance and cost-effective nature, nickel catalysts for photoredox C‒H functionalization have received significant attention. In this review, we highlight the

• transformations have become one of the most reliable and basic tools for designing and manufacturing biologically relevant molecules and functional materials [1][2][3][4]. The formation of highly chemo-, regio-, and stereoselective products with excellent yields is the key reason for transition-metal catalysis as

• ‒C) and carbon–heteroatom bonds for the construction of complex organic molecules by nickel catalysis significantly improved the atom-, step-, and resource economy by avoiding the substrate prefunctionalizations (Scheme 1) [26][27][28][29][30]. The nickel-catalyzed oxidative C‒H functionalization

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF₃·OEt₂ catalysis

• Karthikeyan Soundararajan,
• Helen Ratna Monica Jeyarajan,
• Raju Subimol Kamarajapurathu and
• Karthik Krishna Kumar Ayyanoth

Beilstein J. Org. Chem. 2021, 17, 2186–2193, doi:10.3762/bjoc.17.140

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• fields of biomedicine, sensing or catalysis, for instance. In addition, some review articles on the respective architectures and polymers in principle are listed. Responsive polymers with UCST behavior In this section, we would like to give the reader a brief overview and update of known polymeric

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• with 5-iodoindole (182) in the presence of thiourea and a recyclable CuO nanoparticle catalyst (Scheme 26) [116]. This heterogeneous catalysis strategy bypasses the use of unpleasant aryl thiols, which are generally coupled with other aryl halides in the presence of transition-metal catalysts for

Enantioenriched α-substituted glutamates/pyroglutamates via enantioselective cyclopropenimine-catalyzed Michael addition of amino ester imines

• Zara M. Seibel,
• Jeffrey S. Bandar and
• Tristan H. Lambert

Beilstein J. Org. Chem. 2021, 17, 2077–2084, doi:10.3762/bjoc.17.134

• substitution is discussed. Compared to other methods, this protocol allows for a broader and more enantioselective access to pyroglutamate derivatives. Keywords: Brønsted base; cyclopropenimine; enantioselective catalysis; Michael addition; pyroglutamate; Introduction α-Substituted glutamates have value as

• only up to 84% ee [36]. Phase-transfer catalysis has been employed for the enantioselective addition of an alanine imine derivative, although the selectivity achieved in this case was only 64% ee [37]. In a related work, enantioselectivities of up to 90% ee were realized, but the procedure required an

• reactivity might be sufficient to overcome the reactivity limitations of pronucleophiles derived from other α-amino esters [42]. In this paper, we describe the use of cyclopropenimine catalysis for the enantioselective catalytic Michael reaction of α-substituted amino ester imines. Results and Discussion To

Correction: One-pot multicomponent green Hantzsch synthesis of 1,2-dihydropyridine derivatives with antiproliferative activity

• Giovanna Bosica,
• Kaylie Demanuele,
• José M. Padrón and
• Adrián Puerta

Beilstein J. Org. Chem. 2021, 17, 2026–2027, doi:10.3762/bjoc.17.130

• 10.3762/bjoc.17.130 Keywords: antiproliferative activity; 1,2-dihydropyridines; green Hantzsch synthesis; heterogeneous catalysis; one-pot multicomponent reaction; The authors noticed that the E-factor (E) was calculated using a wrong Equation 2 in the original publication: The correct Equation 2 should

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• of the glycosidic bond. In this system, the SEE was hydrolytically inactive and the acid catalysis activated the C-1 at the reducing end efficiently to promote chain-elongation. Immobilized catalysis provided cellulose analogues with very high crystallinity. A synthetic mutant enzyme of endoglucanase

• acceptor. This process is repeated iteratively allowing for an exponential length growth, while maintaining control over the elongation. Beside more common LGs such as phosphates, thioethers, and imidates, ynenoate donors activated using Au(I) catalysis were successfully employed in an iterative strategy

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• synthesis of biologically relevant coumarins in aqueous medium [21]. Catalysis is one of the fundamental pillars of green chemistry [22], and the transition-metal-catalyzed synthesis of coumarins has been reviewed by Sharma et al. [23]. More recently, Kanchana et al. published an account on the palladium

• . Catalysis via covalent bonding Organocatalysts made from chiral secondary amines have been widely used in the last years. According to Jørgensen, in general, the carbonyl functionalization employing amine catalysts can be separated in four different types [29]. When aldehydes are employed, both

• stereoselective one-pot procedure for the synthesis of five-membered annulated coumarins 28 was described by the group of Enders [40]. Using dual catalysis, with a cinchona primary amine derivative 22 and silver carbonate, a series of functionalized coumarin derivatives 28 were obtained in good yields (up to 91

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• (Scheme 7A). Beckhaus and Doye reported cyclization processes mediated by titanium catalysis, that led to pyridinone derivatives or external cycloamines via an intramolecular titanium-catalyzed C–H hydroaminoalkylation [72][73][74]. In these works, two titanium catalysts were studied, tetrakis

• synthesis of biologically active molecules. Based on the examples mentioned above, there is a specific preference for studies of amine derivatives. However, different functional groups that may go well along with titanium catalysis need still to be explored. Vanadium-catalyzed C–H activation Vanadium is the

• increasing the overall yield. The resulting eight-step synthesis could be scaled to produce more than 100 kg of compound 41 [109]. Based on what was presented so far, vanadium catalysis is mainly applied as one of the steps involved in a total synthesis that usually leads to the formation of a valuable

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• biologically active small molecules and complex peptides. Keywords: bioactive molecules; 3d transition metals; late-stage functionalization; manganese catalyst; sustainable catalysis; Introduction Manganese, a 3d transition metal, allows for a potentially ideal sustainable catalytic system because of the

• excluded. This late-stage process by Mn catalysis, electrochemistry, and visible-light catalysis exhibits high value as a sustainable tool to investigate problematic synthetic transformations. Recently, the Ackermann group disclosed a convenient manganese-catalyzed late-stage C–H azidation of bioactive

• ® (antiplatelet), Gleevec® (anticancer), and augmentin (antibiotic), also contain the benzylic amine motif. Therefore, C–H amination is synthetically important for the diversification of biologically active molecules. Transition metal catalysis has set the stage for C–H amination processes in organic syntheses

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• disclosed here are an improvement compared to the state of the art. For example, addition product 1c has been obtained in 93% conversion before using 10 mol % TPP, 3 equiv c and heating the reaction mixture for 8 h under refluxing conditions [14]. However, with base catalysis (KOt-Bu) even better results

• like structures were observed [24]. A more efficient transformation of acrylamide can be obtained with base catalysis. Using activated potassium carbonate, a reaction temperature of 40 °C, and 4 h reaction time give typically better conversions than those reported herein with nucleophiles [25]. Next

• prepared with nucleophilic catalysis using 10 mol % N-heterocyclic carbenes such as 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene or 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene. The polymerization was carried out at room temperature for 24 h and no solvent was used. The resulting reaction