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

• photocycloaddition of coumarins 202 (Scheme 31) [89]. The proposed mechanism for this reaction is similar to that proposed by Bach and Krische, proceeding via a key hydrogen bonding complex 203. Interestingly, this catalyst allowed for reactivity with lactones, whereas Bach’s catalysts are limited to lactams. Yoon

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• hydroxy moiety at the carbonyl carbon of IIIb further drove the cyclisation to afford the bromomethylcoumarin 4a. Conclusion In summary, we reported the first protocol on the quaternary phosphonium salt-mediated direct synthesis of cinnamyltriazoles and 3-(bromomethyl)coumarins from Morita–Baylis–Hillman

• for the synthesis of 3-(bromomethyl)coumarins. Literature-reported cycloaddition reactions of MBH acetates involving azides and alkynes [24][25][26][27][28]. Synthetic methodologies for triazolations of MBH adducts. a) Literature-reported indirect triazolation of MBH adducts [32][33]. b) This work

• -(bromomethyl)coumarins from MBH adducts. Supporting Information Supporting Information File 98: Compound characterization data and NMR spectra. Acknowledgements The authors thank the institute for the necessary infrastructure. Funding The authors thank the DST-SERB Government of India (file no: YSS/2014

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

• have also been employed to synthesize such chiral oxygen-containing heterocyclic compounds. Feringa’s group reported the highly regio- and enantioselective copper-catalysed direct conjugate addition of Grignard reagents to chromones and coumarins (Scheme 5) [28][29]. A variety of Grignard reagents

• , including linear and secondary alkylmagnesium reagents and various chromones and coumarins, were tolerated by the catalytic system, providing the products with a high yield and enantioselectivity. It was also demonstrated that the addition products could be used for further transformations in order to

• , it was shown that upon the treatment with an amine, this enolate produced the final chiral amide product with a good yield (82%) and ee (96%). While the methodology for the ACAs of Grignard reagents to chromones and coumarins has been established successfully, quinolones remained challenging

Cascade trifluoromethylthiolation and cyclization of N-[(3-aryl)propioloyl]indoles

• Ming-Xi Bi,
• Shuai Liu,
• Yangen Huang,
• Xiu-Hua Xu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2020, 16, 657–662, doi:10.3762/bjoc.16.62

• esters with AgSCF3 for the synthesis of trifluoromethylthiolated coumarins (Scheme 1b) [28]. In 2016, Liu exploited the tandem trifluoromethylthiolation/cyclization of N-arylpropiolamides to construct the SCF3-substituted spiro[4,5]trienones (Scheme 1c) [29]. In the same year, Zhang and Chen disclosed

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• coumarins and indoles: Coumarins and indoles are a large class of compounds gifted with a rich and attractive chemistry. They are found in numerous bioactive natural and nonnatural products. Therefore, a lot of work has been devoted to the construction of diverse intricate molecules containing these

• triflyl chloride (64) by SET gives the highly energetic compound 66, which combines with 88 to give 94. The oxidation of 94 by 92 generates an intermediate 95, which, upon further deprotonation, produces the desired product 89 (Figure 14). C–H lactonization: synthesis of benzo-3,4-coumarins Benzo-3,4

• -coumarins are a key intermediate for diverse natural products, and they have already been synthesized by various research groups with different procedures [132][133][134][135][136][137][138]. Inspired by previous work, Gomez and co-workers reported the preparation of benzo-3,4-coumarins using photoredox

Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin: experimental and computational evidence for intramolecular and intermolecular C–F···H–C bonds

• Vuyisa Mzozoyana,
• Fanie R. van Heerden and
• Craig Grimmer

Beilstein J. Org. Chem. 2020, 16, 190–199, doi:10.3762/bjoc.16.22

• : DFT; F···H hydrogen bond; fluorinated phenylcoumarin; Pechmann reaction; through-space coupling; Introduction Coumarins constitute one of the big classes of naturally occurring compounds. The first coumarin was isolated from the tonka bean (Dipteryx odorata) in 1820 and, to date, more than 1300

• coumarins have been identified from natural sources [1][2]. Coumarins have been reported to play a vital role as food and cosmetics constituents, cigarette additives, and dye-sensitized solar cells [3][4]. In addition, coumarins possess some biological activities such as anti-inflammatory [5], antitumor [6

• ], anti-oxidant [7], antibacterial [8], hepatoprotective, anticoagulant, antiviral and antithrombotic activities [9]. The variety of uses of these compounds resulted in an increase in demand for large quantities of coumarins. Due to an insufficient natural supply to meet this demand for these compounds

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

Catalyst-free assembly of giant tris(heteroaryl)methanes: synthesis of novel pharmacophoric triads and model sterically crowded tris(heteroaryl/aryl)methyl cation salts

• Rodrigo Abonia,
• Luisa F. Gutiérrez,
• Braulio Insuasty,
• Jairo Quiroga,
• Kenneth K. Laali,
• Chunqing Zhao,
• Gabriela L. Borosky,
• Samantha M. Horwitz and
• Scott D. Bunge

Beilstein J. Org. Chem. 2019, 15, 642–654, doi:10.3762/bjoc.15.60

• aldehydes, chromone aldehydes, and fluorene aldehydes (Ar2CHO) and coumarins (Ar3) in 1:1:1 ratio to form the corresponding tris(heteroaryl)methanes (Ar1Ar2Ar3)CH along with (Ar1Ar1Ar2)CH triads. A series of new 2:1 triads were also synthesized by coupling substituted indoles with Ar2CHO. The coupling

• ternary heteroarylmethane-inspired hybrids by coupling diversely substituted indoles (Ar1) with quinoline aldehydes, quinolone aldehydes, chromone aldehydes, and fluorene aldehydes (Ar2CHO) and coumarins (Ar3) in 1:1:1 ratio by simple reflux in ethanol solvent to form the corresponding highly crowded tris

• synthesis of ternary heteroarylmethane-inspired hybrids is presented, by coupling quinoline aldehydes, quinolone aldehydes, chromone aldehydes, and fluorene aldehydes with substituted indoles and coumarins. The method enabled the synthesis of novel libraries of giant (Ar1Ar1Ar2)CH and (Ar1Ar2Ar3)CH triads 8

Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

• Christiane Schultze and
• Bernd Schmidt

Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278

• defined order. One class of products, pyrano[2,3-f]chromene-2,8-diones, were inaccessible through direct RCM of an acrylate, but became available from the analogous allyl ether via an assisted tandem catalytic RCM/allylic oxidation sequence. Keywords: coumarins; heterocycles; isomerization; olefin

• metathesis; ruthenium; Introduction Naturally occurring coumarins and synthetic derivatives have attracted considerable attention, because many of these compounds are pharmacologically active [1][2][3][4]. Their activity profiles are quite diverse and range from anticoagulant via anti-infective, anticancer

• to antineurodegenerative activities [2][3]. The majority of natural coumarins are secondary metabolites isolated from plants [5][6][7]. A commonly used taxonomy for these natural products (which has been extended to the non-natural analogues) is based on the coumarin structure (Figure 1) [4][8]. It

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• -withdrawing substitutions 7 with 4-hydroxycoumarin (34b) at 70 °C within short reaction times. All aromatic aldehydes 7 reacted with 4-hydroxycoumarin (34b) to form bis-coumarins bearing electron-donating groups, electron-withdrawing groups, and halogens 72 in very short reaction times and in high yields. In

• ]octane chloride 71 was introduced as a highly efficient, reusable, general, and nanostructured catalyst for the synthesis of bis-coumarins 72 and spiropyrans 74 and 75 (Scheme 12) [57]. A silica-bonded sulfoimidazolium chloride 76 was prepared nearly similar to the previous example. After producing

• for the synthesis of bis-coumarins and spiropyrans. The catalytic application of a silica-bonded sulfoimidazolium chloride for the synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones. The synthetic route of the SBA-15-Ph-SO3H and its catalytic applications for the synthesis of 2H-indazolo

Microfluidic light-driven synthesis of tetracyclic molecular architectures

• Javier Mateos,
• Nicholas Meneghini,
• Marcella Bonchio,
• Nadia Marino,
• Tommaso Carofiglio,
• Xavier Companyó and
• Luca Dell’Amico

Beilstein J. Org. Chem. 2018, 14, 2418–2424, doi:10.3762/bjoc.14.219

• synthetic method for the direct assembly of highly functionalized tetracyclic pharmacophoric cores. Coumarins and chromones undergo diastereoselective [4 + 2] cycloaddition reactions with light-generated photoenol intermediates. The reactions occur by aid of a microfluidic photoreactor (MFP) in high yield

• suited for a broad range of coumarins 2 and chromones 3, used as precursors for the direct generation of the tetracyclic scaffold 4 and 5, with high synthetic performances (up to >98% yield) and complete diastereocontrol (>20:1). Additionally, manipulations of the naphthochromenone scaffold 4 give access

• 7-substituted coumarins furnished the corresponding cyclic products 4f–h in moderate to excellent yields (41 to >98%) in a pure diastereoisomeric form. As a limitation of the present microfluidic photochemical method, thioxocoumarin 2e showed poor reactivity under the titled reaction conditions

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• group further demonstrated that the head group plays a crucial role in determining the activity against Trypanosoma brucei with another set of novel S-MGBs, structurally analogous to distamycin [101]. Coumarins are a group of phenolic compounds with excellent cytotoxic and antiviral properties. Again

• , dihydrofuranocoumarins are another class of coumarins possessing anticancer activities. Recently, Ahmadi et al. identified several dihydrofuranocoumarins, especially grandivittin (GRA), from Ferulago macrocarpa (Fenzl) Boiss., and their mechanism of minor groove DNA binding and antibacterial, cytotoxic and antioxidant

One-pot preparation of 4-aryl-3-bromocoumarins from 4-aryl-2-propynoic acids with diaryliodonium salts, TBAB, and Na₂S₂O₈

• Teppei Sasaki,
• Katsuhiko Moriyama and
• Hideo Togo

Beilstein J. Org. Chem. 2018, 14, 345–353, doi:10.3762/bjoc.14.22

• coumarins arises from the fact that the coumarin skeleton is present in many natural products extracted from plants [1][2][3] and some of them show potent pharmacological activities, such as antidepressant [4], antimicrobial [5][6], antioxidants [7][8], anti-inflammatory [9][10], antinociceptive [11

• ], antitumor [1], antiasthmatic [12], and antiviral including anti-HIV [13][14]. Comprehensive synthetic studies of coumarins and their derivatives have been carried out [15][16]. Typically, coumarins are prepared by the acid-catalyzed condensation of 2-alkynoic acids and phenols or the condensation of β

• [27], with R-CH=O/(n-Bu)4NBr (TBAB, cat.)/K2S2O8 at 90 °C [28], with ArSO2H/Eosin Y(cat.)/tert-butyl hydrogen peroxide (TBHP) at rt [29], and with ArSO2NHNH2/n-Bu4NI(cat.)/TBHP at 80 °C [30]. In addition, the formation of coumarins via the bromine-radical-mediated reaction of aryl 2-alkynoates with

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• ]. After optimisation of the reaction conditions in batch, the optimal reaction conditions were established in a continuous-flow reactor at a flow rate of 100 µL min−1 at 60 °C for 40 min. The substrate scope was evaluated on 11 coumarins and showed that both electron-rich and electron-deficient functional

• groups were tolerated (Scheme 38). Zou and co-workers applied the conditions described by Langlois or Baran (CF3SO2Na/t-BuOOH/cat. Cu(II) or CF3SO2Na/t-BuOOH, respectively) for the trifluoromethylation of coumarins but no reaction was observed. By testing other oxidants, they found that Mn(OAc)3 was a

• good oxidant for this reaction and allowed to carry out the trifluoromethylation exclusively at the α-position of the carbonyl group in the pyranone ring. The substrate scope was large and included 17 coumarins, 2 quinolines and 3 pyrimidinones. With coumarins bearing electron-donating groups on the

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• (104) led to the formation of 1,3-indanedione derivatives 105 in yields of 63–70% (Scheme 59) [72]. Nucleophilic displacement of the triphenylphosphonium group in α,β-di(alkoxycarbonyl)vinylphosphonium salts: Coumarins are an important class of natural compounds [73]. Yavari et al. developed a method

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• showed that benzimidazoles, Biginelli adducts, dihydropyridines, furans, pyrans, pyridinones, and thiophenes had a high representation of intrinsic greenness; whereas, a high proportion of MCRs producing chromene-4-ones, coumarins, indoles, and pyrazoles had low probabilities of achieving intrinsic

Solvent-free, visible-light photocatalytic alcohol oxidations applying an organic photocatalyst

• Martin Obst and
• Burkhard König

Beilstein J. Org. Chem. 2016, 12, 2358–2363, doi:10.3762/bjoc.12.229

• catalyst was reported [15], which was also used for cyclization to form coumarins [16]. In this work, we focus on benzylic alcohols as substrates since their oxidation to the corresponding carbonyl compounds can be simply performed in acetonitrile/water mixtures. Thus, they are suitable model substrates

Three new trixane glycosides obtained from the leaves of Jungia sellowii Less. using centrifugal partition chromatography

• Luíse Azevedo,
• Larissa Faqueti,
• Marina Kritsanida,
• Antonia Efstathiou,
• Despina Smirlis,
• Gilberto C. Franchi Jr,
• Grégory Genta-Jouve,
• Sylvie Michel,
• Louis P. Sandjo,
• Raphaël Grougnet and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2016, 12, 674–683, doi:10.3762/bjoc.12.68

• sesquiterpenes including a rare skeleton (trixane). Only few of them were described from the genus Jungia along with polyacetylenes, coumarins and flavonoids [6][7][24][25][26]. Globally, the tested glycosylated sesquiterpenes displayed no or weak activity against Leishmania strains, and displayed no

Biosynthesis of α-pyrones

• Till F. Schäberle

Beilstein J. Org. Chem. 2016, 12, 571–588, doi:10.3762/bjoc.12.56

• ), represent widely exploited building blocks in synthetic chemistry. Examples are the syntheses of compounds like α-chymotrypsin, coumarins, pheromones, and solanopyrones [1]. Known biological functions reach from intermediates and end products in primary metabolism to signaling molecules and molecules which

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• ) [63]. In 2010 and 2011, Wang demonstrated that the versatile β-unsaturated α-ketoesters 87 are capable of participating in multiple cascades, initiated by Michael addition of preformed stable enols 137 and 138. As a result, this methodology provided a highly efficient route to coumarins 139 and

Genicunolide A, B and C: three new triterpenoids from Euphorbia geniculata

• Alia Farozi,
• Javid A. Banday and
• Shakeel A. Shah

Beilstein J. Org. Chem. 2015, 11, 2707–2712, doi:10.3762/bjoc.11.291

• -3β,25-diol [21]. In addition, nor-isoprenoids and coumarins have also been reported from few species of Euphorbia [22][23][24]. Euphorbia geniculata Orteg. [25][26], is a wild weed found in the Jammu region of India [27]. The plant is locally used for the treatment of bacterial infections and

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• further oxidation. SCPC oxidations that take place with varying success include toluene to benzaldehyde and benzoic acid [25], cyclohexane to cylohexanone [26], benzylic and allylic alcohols to carbonyl compounds [27] and alkene epoxidations [28]. Conventional syntheses of coumarins, which are important

DBU-promoted carboxylative cyclization of o-hydroxy- and o-acetamidoacetophenone

• Wen-Zhen Zhang,
• Si Liu and
• Xiao-Bing Lu

Beilstein J. Org. Chem. 2015, 11, 906–912, doi:10.3762/bjoc.11.102

• thermodynamically stable coumarins. Importantly, the use of an intramolecular in situ trap avoids the problem of decarboxylation during workup. In case of o-acetamidoacetophenones, an acyl migration from nitrogen to carbon was observed. The cross experiment showed that the N to C acyl shift occurred

Effect of cyclodextrin complexation on phenylpropanoids’ solubility and antioxidant activity

• Miriana Kfoury,
• David Landy,
• Lizette Auezova,
• Hélène Greige-Gerges and
• Sophie Fourmentin

Beilstein J. Org. Chem. 2014, 10, 2322–2331, doi:10.3762/bjoc.10.241

• , cinnamon, etc). PPs play a vital role in plants integrity and defense against biotic or abiotic stresses and are considered as “secondary metabolites” [1]. They are divided in several major classes such as coumarins, flavonoids, phenylpropenes and hydroxycinnamic acids [2]. PPs have an important

The myxocoumarins A and B from Stigmatella aurantiaca strain MYX-030

• Tobias A. M. Gulder,
• Snežana Neff,
• Traugott Schüz,
• Tammo Winkler,
• René Gees and
• Bettina Böhlendorf

Beilstein J. Org. Chem. 2013, 9, 2579–2585, doi:10.3762/bjoc.9.293

• to be transformed into actively growing cultures again. Coumarins in general constitute a large group of bioactive natural products, mostly isolated from plants. Most of these plant-derived compounds are polyphenols that are often further modified by most diverse functionalization reactions, such as