Nitroalkene reduction in deep eutectic solvents promoted by BH₃NH₃

• Chiara Faverio,
• Monica Fiorenza Boselli,
• Patricia Camarero Gonzalez,
• Alessandra Puglisi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2021, 17, 1041–1047, doi:10.3762/bjoc.17.83

• to the first run. AB-mediated reductions of nitrostyrenes 3a–h. AB-mediated reductions of nitrostyrenes 1, 3a, and 3c using DESs B and D. AB-mediated reductions of nitroalkenes 5a–f. Recovery and recycling experiments in the AB-mediated reduction of nitrostyrene 3h to afford nitroalkane 4h

Kinetics of enzyme-catalysed desymmetrisation of prochiral substrates: product enantiomeric excess is not always constant

• Peter J. Halling

Beilstein J. Org. Chem. 2021, 17, 873–884, doi:10.3762/bjoc.17.73

• details of these changes, subject to maintaining the overall thermodynamic relationship. With the parameter set used in these simulations, an increase in Keq alone mainly caused reductions in k−1 and k−2R, partly offset by an increase in k−3R. The examples of Figure 2 and Figure 3 above were for a case

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• , such as reductions, eliminations, as well as C–O, C–N, or C–C bond formations (Scheme 31). α-(Trifluoromethyl)propargylium has also been suggested as an intermediate in superacid-mediated Friedel–Crafts reactions [86]. When [α-(trifluoromethyl)propargyl]allyl silyl ether 120 was added to a

Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• reductions in solution being treated with an alkali metal or thallium amalgam yielding in semiquinonate and then the catecholate species, respectively (Scheme 4). The corresponding semiquinonates could be also generated in a solution in the reaction with Mn2(CO)10 under irradiation with visible light. The

• potential values of 2-substituted malononitriles and 2-substituted acetylacetones are usually higher than those of o-quinones, so that in the case of 6b and 6d two first distinct waves could be attributed to subsequent reductions of the dioxolene fragment. Further reductions correspond to processes on the

Secondary metabolites of Bacillus subtilis impact the assembly of soil-derived semisynthetic bacterial communities

• Heiko T. Kiesewalter,
• Carlos N. Lozano-Andrade,
• Mikael L. Strube and
• Ákos T. Kovács

Beilstein J. Org. Chem. 2020, 16, 2983–2998, doi:10.3762/bjoc.16.248

• various interactions between them occurred. Nevertheless, we could observe statistically significant reductions of the two genera, Lysinibacillus and Viridibacillus, in communities supplemented with the NRP-producing B. subtilis wild type strain. In contrast, in communities supplemented with the NRP

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through “turn-on” fluorescence response

• Rakesh Biswas,
• Surya Ghosh,
• Shubhra Kanti Bhaumik and
• Supratim Banerjee

Beilstein J. Org. Chem. 2020, 16, 2728–2738, doi:10.3762/bjoc.16.223

• reductions were noticed for the N ≥ 10 derivatives (Figure 2a and Supporting Information File 1, Table S1), with the highest change being exhibited by PBIm14. These observations suggested that in going to higher concentrations, there was a gradual increase in the aggregation of the longer chain derivatives

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• supports the mechanically interlocked structure for NDIRot in analogy to similar structures investigated by tandem mass spectrometry earlier [35][40]. Cyclic voltammograms of NDIRot show two reversible reductions E1/2red1 and E1/2red2 independent of the used solvent (pure DCE or DCE/CH3CN 1:1, Figure S11

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

Lipophilicity trends upon fluorination of isopropyl, cyclopropyl and 3-oxetanyl groups

• Benjamin Jeffries,
• Zhong Wang,
• Robert I. Troup,
• Anaïs Goupille,
• Jean-Yves Le Questel,
• Charlene Fallan,
• James S. Scott,
• Elisabetta Chiarparin,
• Jérôme Graton and
• Bruno Linclau

Beilstein J. Org. Chem. 2020, 16, 2141–2150, doi:10.3762/bjoc.16.182

• when the “cyclisation” operation is achieved from geminal motifs (Figure 7B). Significant logP reductions are observed, especially from the internal geminal fluorination motif as in G9 to E2 (0.72 logP units). Starting from a trifluoromethyl group (Figure 7C), similar logP reductions are achieved (e.g

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• heteroarene 6.3. Other reductive fragmentations Another organophotocatalytic strategy for accessing C(sp3) radicals relies on the reductive homolytic cleavage of easily reducible functional groups. In this case, the substrates can act as acceptors in SET reductions, and the alkyl radical is obtained after the

• SET reductions to generate the corresponding radical anions (Scheme 21c). Organophotocatalysis has been successfully exploited to promote these SETs and access charged alkenyl and aryl radicals. The reduction of carbon–heteroatom double bonds is especially easy and leads to the formation of ketyl

• a suitable Michael acceptor 24.2 to obtain the corresponding allylation product 24.3 after a desulfonylation. Enones can also be subject to SET reductions through photoredox catalysis, and this can lead to [2 + 2] cycloadditions [2][108]. Similar intermediates can also be generated through the

Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents

• Yafei Guo and
• Syuzanna R. Harutyunyan

Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90

• functionalised alkyl chains at the β-position of the alkenylpyridines, the catalytic system also showed a high functional group tolerance, and thus allowing straightforward chemical transformations of the addition products, including, for example, reductions, cycloadditions, and coupling reactions (Scheme 15B

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• the previously reported cNMInEE series (n = 1, 2, 3) it was also possible to observe one reversible oxidation and four reductions, the first two being reversible [32]. The first oxidation potentials (EOx1) vary from 0.62 to 1.09 V, while the first reduction potentials (ERed1) range from −1.54 to −0.60

Copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters with chiral phenol–carbene ligands

• Shohei Mimura,
• Sho Mizushima,
• Yohei Shimizu and
• Masaya Sawamura

Beilstein J. Org. Chem. 2020, 16, 537–543, doi:10.3762/bjoc.16.50

• work of Stryker and co-workers on triphenylphosphine-stabilized copper hydride complexes [1][2], copper hydrides have been widely used for conjugate reductions of α,β-unsaturated carbonyl compounds [3]. Especially a chiral copper catalyst combined with a stoichiometric amount of a silane reagent, which

• both the reactivity and selectivity (Table 1, entries 7–10), while the replacement of the ethoxy groups of (EtO)2MeSiH with methoxy or trimethylsilyloxy groups resulted in only moderate reductions in the enantioselectivity and high yields. At the same time, trialkoxysilane (EtO)3SiH and polymeric

• reductions. The phenolic N-substituent of the chiral NHC ligand was essential for the high enantioselectivity. Good enantioselectivities were observed for the various (Z)-configured substrates with different β-substituents. Further investigations on the catalyst development based on this knowledge are

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• . The use of either homoleptic or heteroleptic complexes in atom transfer radical addition (ATRA) reactions, reductions, oxidations, proton-coupled electron transfer (PCET) reactions, and reactions based on energy transfer will be discussed. 1 Homoleptic Cu(I) complexes Homoleptic complexes based on

• can be readily obtained in a crystalline form. Herein, we will report their use in ATRA reactions, reductions, oxidations, as well as in PCET and energy transfer reactions. 2.1 ATRA reactions In 2015, Reiser and co-workers reported the synthesis of a novel copper-based heteroleptic complex bearing a

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

• summarized the background and recent advances and arranged this article to provide a systematic description of electrochemical reactions in which chirality has been induced using these three sources (Figure 1). Chemically modified chiral electrodes Electrochemical asymmetric reductions using chiral

• of a poly-ʟ-valine 6 coated graphite cathode for asymmetric electrochemical reductions in two consecutive reports. In the first communication, they carried out the asymmetric reduction of prochiral activated olefins 5 and 8, affording 7 and 9 with optical yields of 25% and 43%, respectively (Scheme 3

Experimental and computational electrochemistry of quinazolinespirohexadienone molecular switches – differential electrochromic vs photochromic behavior

• Eric W. Webb,
• Jonathan P. Moerdyk,
• Kyndra B. Sluiter,
• Benjamin J. Pollock,
• Amy L. Speelman,
• Eugene J. Lynch,
• William F. Polik and
• Jason G. Gillmore

Beilstein J. Org. Chem. 2019, 15, 2473–2485, doi:10.3762/bjoc.15.240

• from both 3b and 1b. A (presumably two-electron) reduction peak was observed for 3a but only one return oxidation wave was observed. Upon repeated scanning the two one-electron reductions of 5a → 5a•− → 5a2− were observed, but still only a single (likely two-electron) return oxidation peak was observed

Naphthalene diimides with improved solubility for visible light photoredox catalysis

• Barbara Reiß and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201

• the reference NDI 1 and the cNDI 2 (due to the better solubility) were determined in comparison by cyclic voltammetry in CH2Cl2 and in the presence of 0.1 M n-Bu4PF6 as conducting salt (see Supporting Information File 1). The cyclic voltagram of NDI 1 shows two reversible reductions and one

• reductions of cNDI 2 to the radical anion 2•− were observed at E½(2/2•−) = −1.06 V and to the dianion 22− at E½(2•−/22−) = −1.50 V and show the electronic effect of the two n-propylamino substituents. Additionally, two reversible oxidations were observed at E½(2•+/2) = +0.99 V and E½(22+/2•+) = +1.40 V which

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• reductions with a NaBH4/ZnCl2 mixture or ʟ-Selectride®, respectively, to form aziridine alcohols (2S,1'R,1''R)-37 and (2S,1'S,1''R)-37. Reductive opening of the aziridine ring with concomitant removal of the chiral auxiliary produced protected (2S,3R)-35 and (2S,3S)-35 which were hydrolyzed to xestoaminol C

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• electrophilicity made lanthanides a catalyst of choice. Lanthanum complexes are widely used in synthetic chemistry for cycloadditions, reductions, benzimidazole syntheses, Biginelli reactions, hydrophosphinations of unsaturated substrates, double hydrophosphinylations of unactivated nitriles, Grignard additions, C

N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• processes. Conclusion One of the major current challenges in photoredox catalysis is the design of chromophores suitable for the most reductive chemical reactions, like for instance reductions by alkaline metals, affording reaction conditions that are easier to handle. While solid sodium comes up with a

Unnatural α-amino ethyl esters from diethyl malonate or ethyl β-bromo-α-hydroxyiminocarboxylate

• Eloi P. Coutant,
• Vincent Hervin,
• Glwadys Gagnot,
• Candice Ford,
• Racha Baatallah and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2853–2860, doi:10.3762/bjoc.14.264

• condensations of diethyl malonate on aldehydes, reductions of the resulting alkylidenemalonates, the preparation of the corresponding α-hydroxyimino esters and their final reduction. This synthetic pathway turned out to be general although some unexpected limitations were encountered. The synthetic

• ensuing reduction of 6u using sodium borohydride led to a somewhat better yield of compound 3u (as estimated by 1H NMR), side products resulting from over-reductions of the ester moieties were still observed. It is only when switching to tetramethylammonium borohydride that this was alleviated and the

Synthesis of unnatural α-amino esters using ethyl nitroacetate and condensation or cycloaddition reactions

• Glwadys Gagnot,
• Vincent Hervin,
• Eloi P. Coutant,
• Sarah Desmons,
• Racha Baatallah,
• Victor Monnot and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2846–2852, doi:10.3762/bjoc.14.263

• conditions could be detrimental to the stability of some of these α-nitro acrylates. In the past, such reductions have been achieved under fairly uncommon conditions (NaBH4 in a mixture of isopropanol and chloroform over a large proportion of silica gel) [11][12]. However, when tried, no real overall

• 14. Syntheses of α-amino ester 18 and piperazinediones 23a,b. Syntheses of α-hydroximino ester 29 and α-amino ester 36. Synthesis of α-amino ester 43. Synthesis and reductions of α-nitro acrylates into α-amino esters. Supporting Information Supporting Information File 254: Experimental and copies of

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• in 91% yield. The ethyl ester was then smoothly reduced with DIBAL to the benzyl alcohol. While the in-process analysis (TLC and HPLC) indicated quantitative reduction, the isolated yields from the reductions were only poor to modest despite utilizing standard workup conditions with sodium potassium

Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions

• Nicole C. Neyt and
• Darren L. Riley

Beilstein J. Org. Chem. 2018, 14, 1529–1536, doi:10.3762/bjoc.14.129

• conditions reductions have mostly been limited to soluble reducing agents like DIBAL [7][8][9][10] and superhydride [11] which require special handling or expensive solid-supported borohydride species [12]. Recently, Seeberger and co-workers demonstrated a more cost-effective sodium borohydride-mediated flow

• (Table 1). Under these conditions, aldehyde reductions gave moderate to good yields (68–92%) which were comparable to those observed in batch in a significantly reduced reaction residence time (64 min vs 12 h). When expressed in terms of reactor space-time productivity (grams of product produced per

• ketones The striking difference in relative reactivity between the ketones and the aldehydes on the flow system allowed us to demonstrate selective reductions of aldehydes in the presence of various ketones by simple selection of an appropriate flow rate. This selectivity was shown by the reduction of