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

• catalysts and asymmetric methodologies, a few innovative nonchiral alternative H-donor or halide-binding organocatalysts, like, e.g., tridentate phosphoramides [41], onium salts [42] such as Berkessel's pyridinium systems [43], or Huber's bis-iodo imidazolium [44] and neutral bridged 2,6-diiodo‐3,4,5

Transition-metal-free intramolecular Friedel–Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives

• Tülay Yıldız,
• İrem Baştaş and
• Hatice Başpınar Küçük

Beilstein J. Org. Chem. 2021, 17, 2203–2208, doi:10.3762/bjoc.17.142

• organometallic chemistry and using transition metal catalysts, which need expensive and toxic chemicals. With the increasing interest in these methods, new organocatalysts and reagents that are less toxic, easier to use, readily accessible, and cheap have been developed [37]. In particular, the synthesis of

• arenes using the FCA methods with π-activated alcohols and organocatalysts has begun to be preferred over using conventional reagents, such as organohalogens and transition metal catalysts, which are toxic and require working under harsher conditions [38]. After these developments, the intramolecular FCA

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

• stereogenic centers. Review A plethora of highly effective small‐molecule organocatalysts have enriched the field of organic synthesis [27], including chiral proline derivatives, N‐heterocyclic carbenes, chiral thioureas and Brønsted acids as well as phase‐transfer catalysts (PTC), such as the quaternary

• . 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

• product 17 was obtained in 15 steps with 6% overall yield. Although chiral secondary amines have proved to be particularly useful catalysts, primary amines as organocatalysts in asymmetric synthesis have also played a significant role [36]. For instance, Kim et al. described the enantioselective Michael

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

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• hand, natural amino acids proline and hydroxyproline are functionalized pyrrolidines that have found great application in organic synthesis as chiral organocatalysts in stereoselective processes [93][94]. Cyclizations involving a position in the starting chiral imine Arylation of chiral sulfinyl imines

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• neat for 30 min, or 24 h diluted in an apolar solvent. Both of these conditions proved very efficient even for hindered reagents and displayed good to excellent yields (Scheme 39B). In the search for new biguanide-based organocatalysts for the transesterification of vegetable oils, Glasovac et al

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

• Deniz Tözendemir and
• Cihangir Tanyeli

Beilstein J. Org. Chem. 2021, 17, 494–503, doi:10.3762/bjoc.17.43

• Deniz Tozendemir Cihangir Tanyeli Department of Chemistry, Middle East Technical University, 06800 Ankara, Turkey 10.3762/bjoc.17.43 Abstract Cinchona alkaloid-derived organocatalysts are widely employed in various asymmetric transformations, yielding products with high enantiopurity. In this

• naturally occurring cinchona alkaloids have shown remarkable performance as organocatalysts for stereoselective synthesis in the past decade [1][2][3][4][5][6]. Among them, quinine-derived organocatalysts make a noteworthy appearance in the formation of new stereogenic centres, which can serve as valuable

• building blocks for the construction of more elaborate structures [7][8][9][10][11]. An outstanding class of quinine derived organocatalysts exhibits a bifunctional mode of activation by the incorporation of an acidic unit, such as urea, thiourea, squaramide or sulfonamide moieties, giving rise to the

Direct synthesis of anomeric tetrazolyl iminosugars from sugar-derived lactams

• Michał M. Więcław and
• Bartłomiej Furman

Beilstein J. Org. Chem. 2021, 17, 115–123, doi:10.3762/bjoc.17.12

• widely used as organocatalysts. Such moieties are employed in a number of important synthetic transformations, including the aldol reaction [30], Michael addition [31], Mannich reaction [32], and hydrogenation [33]. We plan to test these possibilities in the near future. Stereochemistry and configuration

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166

• endpoint. However, Nicolaou’s route is the shortest (6 or 7 steps, 9.8–9.2% yield), while Kitahara’s synthesis is the highest-yielding and does not involve the use of expensive transition metals or organocatalysts. Syntheses to generate the C-14 stereocenter via C–N bond formation Two groups implemented

Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• abecarnil, tadalafil, cipargamin, yohimbine, etc. which are used in the treatment of various ailments [14][15]. Apart from their pharmaceutical properties, β-carboline derivatives also found various applications in fields such as organocatalysts, as ligands, and fluorescent probes [16][17][18]. Importantly

NHC-catalyzed enantioselective synthesis of β-trifluoromethyl-β-hydroxyamides

• Alyn T. Davies,
• Mark D. Greenhalgh,
• Alexandra M. Z. Slawin and
• Andrew D. Smith

Beilstein J. Org. Chem. 2020, 16, 1572–1578, doi:10.3762/bjoc.16.129

• trifluoromethyl ketones (Figure 1C) [20]. Over the last twenty years, NHCs have been widely exploited as highly efficient organocatalysts that have found use in numerous applications and were the subject of many extensive reviews [21][22][23][24][25][26]. Among the most common reactive intermediates generated

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• as scavengers of C-centered radicals [9] and selective oxidation organocatalysts (for example, in the oxidation of alcohols to the corresponding carbonyl compounds [10][11]). Recently, highly reactive imidoxyl radicals (Figure 1, II) have found a wide application in the processes of hydrogen atom

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• aliphatic acids and the coupling of the residual chain with various electrophiles. Metal-based catalysts are common in reactions that require a high redox potential for a single electron transfer (SET) procedure to take place. On the other hand, even if organocatalysts have lower redox potentials, they are

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• ]. Among the P-heterocycles with various ring size, the five-membered derivatives received special attention due to their optimal bond angles and shapes [13][14]. Besides their application as ligands [13][15], the five-membered heterocycles may also be valuable organocatalysts in reactions involving a P

• (III)–P(V) redox cycle, such as in catalytic Wittig-, aza-Wittig-, Staudinger-, Appel- and other reactions [16][17][18][19][20][21]. The ring strain of the four- and five-membered derivatives makes them highly susceptible to deoxygenation, thus they are ideal organocatalysts in P(III)–P(V) redox

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

• Faïma Lazreg,
• Marie Vasseur,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

• , the presence of an N-atom in the amidine structure leads to opportunities as ligands and organocatalysts [6][7][8]. N-Sulfonylamidines and N-sulfonylimidates are members of a specific class of these amidines. One initial methodology developed for the formation of sulfonylamidines was based on the

Copper-catalyzed enantioselective conjugate addition of organometallic reagents to challenging Michael acceptors

• Delphine Pichon,
• Jennifer Morvan,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2020, 16, 212–232, doi:10.3762/bjoc.16.24

• -substitution of enals [21]. By using (R)-BINAP (L2)/CuTC in combination with chiral prolinol derivatives L4–6 as organocatalysts, various α,β-functionalized aldehydes were synthesized in good isolated yields (57–74%) and remarkable enantioselectivity (99%) from diethylzinc or dimethylzinc as nucleophiles and

The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

• Itamar L. Gonçalves,
• Rafaela R. da Rosa,
• Vera L. Eifler-Lima and
• Aloir A. Merlo

Beilstein J. Org. Chem. 2020, 16, 175–184, doi:10.3762/bjoc.16.20

• components, which may be substituted symmetrically or unsymmetrically [1]. Applications of this scaffold include complexing agents in anion sensors [2] organocatalysts [3], intermediates in heterocycle synthesis [1] and development of compounds with pharmacological effects [4]. Considering the importance of

The reaction of arylmethyl isocyanides and arylmethylamines with xanthate esters: a facile and unexpected synthesis of carbamothioates

• Narasimhamurthy Rajeev,
• Toreshettahally R. Swaroop,
• Ahmad I. Alrawashdeh,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Seegehalli M. Anil,
• Kuppalli R. Kiran,
• Chandra,
• Paris E. Georghiou,
• Kanchugarakoppal S. Rangappa and
• Maralinganadoddi P. Sadashiva

Beilstein J. Org. Chem. 2020, 16, 159–167, doi:10.3762/bjoc.16.18

• of xanthate esters with amines [18]. Furthermore, many methods have also been reported for the synthesis of cyclic thiocarbamates, and these include reactions of isothiocyanates with aldehydes in the presence of organocatalysts [19][20], reactions of vicinal diols with potassium thiocyanate [21

Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

• Dominika Krištofíková,
• Juraj Filo,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2019, 15, 2948–2957, doi:10.3762/bjoc.15.290

• Bratislava, Mlynská dolina, Ilkovičova 6, 84215 Bratislava, Slovakia 10.3762/bjoc.15.290 Abstract A range of chiral hydrogen-bond-donating organocatalysts was tested in the Ireland–Claisen rearrangement of silyl ketene acetals. None of these organocatalysts was able to impart any enantioselectivity on the

• rearrangements. Furthermore, these organocatalysts slowed down the Ireland–Claisen rearrangement in comparison to an uncatalyzed reaction. The catalyst-free reaction proceeded well in green solvents or without any solvent. DFT calculations showed that the activation barriers are higher for reactions involving

• hydrogen-donating organocatalysts and kinetic experiments suggest that the catalysts bind stronger to the starting silyl ketene acetals than to transition structures thus leading to inefficient rearrangement reactions. Keywords: DFT calculations; green solvents; H-bonding catalysts; Ireland–Claisen

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• transformations using various catalysts as chiral sources has been studied in greater detail than the other strategies mentioned in this review. As per our classification, we further categorize this class into metal catalysts, enzyme catalysts and organocatalysts. Metal catalysts: In 1992, Amundsen and co-workers

• chiral enolates. Organocatalysts: From the outset of electroorganic chemistry, chemists have devoted substantial effort towards applying organocatalysts in electroorganic synthesis. Recent advances integrating organocatalysis and electroorganic synthesis were elegantly presented by Boydston and Ogawa in

• their review article [72]. In this section, we will be presenting a concise description of the use of organocatalysts as chiral inductors in electroorganic synthesis. In 2008, Page, Marken and their group reported a method for electricity-driven asymmetric organocatalytic epoxidation. The percarbonate

1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds

• Vito A. Fiore,
• Chiara Freisler and
• Gerhard Maas

Beilstein J. Org. Chem. 2019, 15, 2603–2611, doi:10.3762/bjoc.15.253

• intermediates that can be transformed intra- or intermolecularly into a wide array of acyclic, carbocyclic and heterocyclic structures. In these processes, the tertiary phosphanes can act as nucleophilic organocatalysts (for reviews, see [1][2][3][4] or be incorporated in the (pre-)final products, typically as

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• separated by column chromatography. Photooxygenation of 3,4-diphenylbutanal (1) with chiral organocatalysts The highly enantioselective synthesis of 3,4-diphenylbutanal (1), according to the procedure developed by Melchiorre, requires the use of noncommercially available sterically bulky silyl ethers [16

• was subjected to photooxygenation in the presence of various organocatalysts: amide 15, imidazolidinone 16, diarylprolinol silyl ethers (S)-17 and (S)-18 which proved the most effective in the photooxygenation of achiral 3-phenylpropanal (Table 1) [14]. The prolinamide-catalyzed reaction furnished

• . All solvents and chemicals used in the syntheses were of reagent grade and were used without further purification. Aldehydes 1 [16][30], 2 [17], 3 [18] and organocatalysts 14 [31], 15 [32], 16 [33] were prepared by known procedures. Silyl ethers of diarylprolinols 17 and 18 were obtained from Sigma

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

• Esther Nieland,
• Oliver Weingart and
• Bernd M. Schmidt

Beilstein J. Org. Chem. 2019, 15, 2013–2019, doi:10.3762/bjoc.15.197

• reaction and as organocatalysts in Diels–Alder reactions [27]. The group of Metrangolo also reported halogen bonding-promoted catalysis in water by exploiting a halogen bonding amino acid, which combines excellent donor properties with good water solubility [28], in addition to their seminal contributions

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• discovered, including HIV-1 reverse transcriptase inhibition activity [6][7][8][9][10][11]. Moreover, their utilization as highly regio- and stereoselective organocatalysts in specific types of chemical tranformations [12][13][14][15][16][17] was introduced, as well. More recently, O-thiocarbamates have been