Identification and determination of the absolute configuration of amorph-4-en-10β-ol, a cadinol-type sesquiterpene from the scent glands of the African reed frog Hyperolius cinnamomeoventris

• Angelique Ladwig,
• Markus Kroll and
• Stefan Schulz

Beilstein J. Org. Chem. 2023, 19, 167–175, doi:10.3762/bjoc.19.16

• , such a synthetic approach would shorten the synthesis from eight to four steps and allow access to both enantiomers of the compounds 12–14. The synthesis started with an enantioselective Michael addition of aldehyde 1 to methyl vinyl ketone (15) catalyzed by (S)-Jørgensen’s organocatalyst S-16, to

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• the enantioselective Michael addition with different rotaxane catalysts (S)-56a/56b/57a/57b and their non-interlocked counterparts. Synthesis of Beer´s [2]rotaxanes 64a/b for anion recognition. Association constants of different anions (used as the Bu4N+ salts) to the [2]rotaxanes (S)-64a/b and the

New advances in asymmetric organocatalysis

• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 240–242, doi:10.3762/bjoc.18.28

• cyclopropenimines exemplify Brønsted base organocatalysts that are useful for diverse reactions not easily accessible by other means. Here, Lambert and co-workers employed this type of catalyst in the formation of pyroglutamates via enantioselective Michael addition of amino ester imines [22]. Phase-transfer

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

• enantioselective Michael addition of ketones 20 to 3-aroylcoumarins 19 [38]. For this transformation, the authors used a cinchona alkaloid-derived primary amine catalyst 22 (Scheme 6a). The study was performed with cyclic and acyclic ketones 20 and various 3-aroylcoumarins 19 and the desired products 21 were

• amine (S)-warfarin analogues 3 could be obtained with moderate to excellent enantiomeric excesses (Scheme 27b). In 2018, Modrocká et al. described the synthesis of 2,3-dihydrofurocoumarins 89 through an enantioselective Michael addition of 4-hydroxycoumarins 1 to β-nitrostyrenes 88, followed by an

• intramolecular cyclization [63]. For this transformation, the authors use a squaramide catalyst 90 to perform the enantioselective Michael addition in 1,4-dioxane at room temperature, as shown in Scheme 28a. Moreover, the group tried a reusable immobilised squaramide catalyst 91, which gave the desired product

Copper catalysis with redox-active ligands

• Agnideep Das,
• Yufeng Ren,
• Cheriehan Hessin and
• Marine Desage-El Murr

Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77

• precursors affords both enantiomers Δ-10 (from CuClO4) and Λ-10 from (Cu(CH3CN)4PF6). UV–vis and circular dichroism spectroscopic studies evidence that the helical chirality exhibited by these two catalysts could be reversed by redox stimuli. These complexes could perform enantioselective Michael addition

• trifluoromethylation of heteroaromatics with redox-active iminosemiquinone ligands. Reversal of helical chirality upon redox stimuli and enantioselective Michael addition with a redox-reconfigurable copper catalyst. Interaction of guanidine-copper catalyst with oxygen and representative coupling products. a4 mol

Asymmetric Michael addition reactions catalyzed by calix[4]thiourea cyclohexanediamine derivatives

• Zheng-Yi Li,
• Hong-Xiao Tong,
• Yuan Chen,
• Hong-Kui Su,
• Tangxin Xiao,
• Xiao-Qiang Sun and
• Leyong Wang

Beilstein J. Org. Chem. 2018, 14, 1901–1907, doi:10.3762/bjoc.14.164

• Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China 10.3762/bjoc.14.164 Abstract A number of upper rim-functionalized calix[4]thiourea cyclohexanediamine derivatives have been designed, synthesized and used as catalysts for enantioselective Michael addition reactions between

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• % ee), which displayed the importance of the calix[4]arene skeleton. We also employed calixarene-based chiral primary amine thioureas 47a and 47b in the enantioselective Michael addition of α,α-disubstituted aldehydes 51 to maleimides 52 (Scheme 14) [50]. The reactions proceeded under mild conditions

• (Scheme 17). Asymmetric Michael addition of 57 to 49 catalyzed by 64 at room temperature afforded the Michael adducts in high yields and moderate to excellent enantioselectivities (Scheme 18). To establish the role of the calixarene backbone on the enantioselective Michael addition, chiral monomeric

• addition of 48 with 49 catalyzed by 47a and 47b. Enantioselective Michael addition of 51 to 52 catalyzed by calix[4]arene thioureas. Synthesis of calix[4]arene-based tertiary amine–thioureas 54–56. Asymmetric Michael addition of 34 and 57 to nitroalkenes 49 catalyzed by 54b. Synthesis of p-tert-butylcalix

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• synthesis and application of a recyclable immobilized analogue of benzotetramisole (BMT) used in a catalytic enantioselective Michael addition/cyclization reactions under continuous-flow conditions (Scheme 11) [60]. Resin-bound catalyst 10 was swollen with dichloromethane in a medium-pressure chromatography

A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

• Mariano Goldberg,
• Denis Sartakov,
• Jan W. Bats,
• Michael Bolte and
• Michael W. Göbel

Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176

• in the field of molecular recognition, however, without being tested as catalysts [5][6][7][8][9][10]. A first example of enantioselective Michael addition has been reported for guanidine 3, albeit with low selectivity [11]. Compounds 4 and 5, inspired by the structure of ptilomycalin A and related

Towards the total synthesis of keramaphidin B

• Pavol Jakubec,
• Alistair J. M. Farley and
• Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104

• pronucleophile to a substituted furanyl nitroolefin catalysed by a bifunctional cinchonine-derived thiourea has been used as the key stereocontrolling step in a new synthetic strategy to the heavily functionalised piperidine core of keramaphidin B. Keywords: bifunctional organocatalyst; enantioselective Michael

• addition; keramaphidin B; nitro-Mannich lactamisation cascade; Introduction Keramaphidin B (1) is a marine alkaloid first isolated by Kobayashi in 1994 from the Okinawan marine sponge Amphimedon sp and has been shown to be cytotoxic against KB human epidermoid carcinoma cells (IC50 0.28 μg/mL) and P388

Organocatalytic and enantioselective Michael reaction between α-nitroesters and nitroalkenes. Syn/anti-selectivity control using catalysts with the same absolute backbone chirality

• Jose I. Martínez,
• Uxue Uria,
• Maria Muñiz,
• Efraím Reyes,
• Luisa Carrillo and
• Jose L. Vicario

Beilstein J. Org. Chem. 2015, 11, 2577–2583, doi:10.3762/bjoc.11.277

• all cases. Keywords: asymmetric diastereodivergent; enantioselective; Michael addition; nitroalkenes; nitroesters; organocatalysis; squaramides; Introduction The absolute stereochemistry of a molecule has a paramount influence on the properties that this compound will have when interacting with

Primary-tertiary diamine-catalyzed Michael addition of ketones to isatylidenemalononitrile derivatives

• Akshay Kumar and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2014, 10, 929–935, doi:10.3762/bjoc.10.91

• of the enantioselective Michael addition of acetone (2a) to isatylidenemalononitrile (3a).a Substrate scope of 1a D-CSA catalyzed asymmetric Michael reaction of ketones 2 with isatylidenemalononitrile derivatives 3.a Supporting Information Supporting Information File 12: Experimental procedures

Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions

• Matthias Leven,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• -dihydroquinolines in optically enriched forms found in a myriad of bioactive natural products and synthetic compounds. Keywords: chromenes; 1,2-dihydroquinolines; enantioselective; Michael addition; organocatalytic; thiochromenes; Introduction Chromenes or benzopyrans and their sulfur and nitrogen analogues are

• , and the power of tandem/domino/cascade-Michael addition reactions promoted by chiral organocatalysts has been intensely studied within this field. In this review, we have outlined some significant works concerning the organocatalytic enantioselective Michael addition reaction from three different

Organocatalytic asymmetric Michael addition of unprotected 3-substituted oxindoles to 1,4-naphthoquinone

• Jin-Sheng Yu,
• Feng Zhou,
• Yun-Lin Liu and
• Jian Zhou

Beilstein J. Org. Chem. 2012, 8, 1360–1365, doi:10.3762/bjoc.8.157

• [26][27]. To construct the C3 quaternary stereogenic carbon center, we have designed a novel cinchona alkaloid-based phosphoramide bifunctional catalyst to realize a highly enantioselective Michael addition of both unprotected 3-alkyl- and 3-aryloxindoles to nitroolefins [28]. Based on these results

Enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes catalyzed by binaphthyl-derived organocatalysts

• Saet Byeol Woo and
• Dae Young Kim

Beilstein J. Org. Chem. 2012, 8, 699–704, doi:10.3762/bjoc.8.78

• Saet Byeol Woo Dae Young Kim Department of Chemistry, Soonchunhyang University, Asan, Chungnam, 336-745, Korea 10.3762/bjoc.8.78 Abstract The highly enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes, promoted by binaphthyl-modified chiral bifunctional

• to the development of asymmetric conjugate additions of 1,3-dicarbonyl compounds to various Michael acceptors [27][28][29][30][31][32][33]. Recently, the groups of Du and Zhou reported a highly enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes catalyzed by chiral

• reported the enantioselective Michael addition of active methines to nitroalkenes [43][44]. Herein, we describe the direct enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinone with nitroalkenes, catalyzed by bifunctional organocatalysts (Figure 1) that bear both central and axial chiral

Stereoselective, nitro-Mannich/lactamisation cascades for the direct synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles

• Pavol Jakubec,
• Dane M. Cockfield,
• Madeleine Helliwell,
• James Raftery and
• Darren J. Dixon

Beilstein J. Org. Chem. 2012, 8, 567–578, doi:10.3762/bjoc.8.64

• synthesised in a four-component one-pot cascade combining an enantioselective Michael addition with the diastereoselective nitro-Mannich/lactamisation cascade. Protodenitration and chemoselective reductive manipulation of the heterocycles could be used to install contiguous and fully substituted stereocentres

• diastereomer 2m isolated in 5% yield. Possible explanations for the observed high stereoselectivities in the nitro-Mannich/lactamisation cascade. Thermodynamically-driven epimerisation of 5-nitropiperidin-2-ones 2m and 2m’. One-pot three/four-component enantioselective Michael addition/nitro-Mannich