Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• which resulted in C3-alkylated pyridines 51. Based on the reactions performed for the catalytic activity of the silyl-iridium complex, the authors proposed a catalytic mechanism (Scheme 11b). The mechanism involves the initial formation of the active silyl-iridium catalyst A which through oxidative

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• formation of the fused cyclobutane acid 162 as the desired precursor for the cyclooctane formation. The ring expansion was achieved in the presence of an iridium catalyst and under blue LED irradiation, via the trapping by TEMPO or O2 of the cyclobutyl radical resulting from decarboxylation, which allowed a

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• electron-withdrawing groups inactivates the iridium catalyst, perhaps by chelation with the carbonyl and the bridging oxygen atom. Computational Computational details All density functional theory (DFT) calculations in this study were carried out with the Gaussian 16, C.01 suite of programs [68]. Geometry

• observed C3-exo-product 15. First, the active iridium catalyst will undergo oxidative addition into the aldehyde C–H bond (Figure 4). Next, the iridium hydride species will undergo exo-η2-coordination with the olefin of MeOBD to generate intermediate IN1b. Insertion of the olefin into the iridium-hydride

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

• for the mode of action of this cascade arylation protocol (Figure 10) [73]. In the photocatalytic cycle, the SET event between the photoexcited iridium catalyst 10-II and the substrate oxalate 33 generates a tertiary carbon-centered radical 10-IV by decarboxylation and the reduced iridium(II

• ]. Notably, this method proceeds through a unique mechanism (Figure 18) involving five steps: i) anion exchange between the iridium catalyst and nickel catalyst; ii) generation of a bromine radical and nickel(I) species in the photocatalytic cycle; iii) hydrogen atom abstraction events between the bromine

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

A complementary approach to conjugated N-acyliminium formation through photoredox-catalyzed intermolecular radical addition to allenamides and allencarbamates

• Olusesan K. Koleoso,
• Matthew Turner,
• Felix Plasser and
• Marc C. Kimber

Beilstein J. Org. Chem. 2020, 16, 1983–1990, doi:10.3762/bjoc.16.165

• -acyliminium intermediate is provided to explain the addition product distribution. Results and Discussion We began our study by using the iridium catalyst Ir[(ppy)2(dtbbpy)]PF6 (17) and the reaction conditions used in the addition of amine nucleophiles to enamides [48][50]. By exploiting these reaction

Photocatalytic deaminative benzylation and alkylation of tetrahydroisoquinolines with N-alkylpyrydinium salts

• David Schönbauer,
• Carlo Sambiagio,
• Timothy Noël and
• Michael Schnürch

Beilstein J. Org. Chem. 2020, 16, 809–817, doi:10.3762/bjoc.16.74

• ). Eosin Y was inefficient under these conditions (Table 1, entry 20). Since [Ru(bpy)3]Cl2 is significantly cheaper than the iridium catalyst, the former was used in further reactions. Regarding the addition of different bases, the yield remained unchanged, when lutidine was added. Potassium carbonate and

Six-fold C–H borylation of hexa-peri-hexabenzocoronene

• Mai Nagase,
• Kenta Kato,
• Akiko Yagi,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2020, 16, 391–397, doi:10.3762/bjoc.16.37

• calculations. The spectra revealed a bathochromic shift of absorption bands compared with unsubstituted HBC under the effect of the σ-donation of boryl groups. Keywords: C–H borylation; hexa-peri-hexabenzocoronene; iridium catalyst; X-ray crystallography; Introduction Polycyclic aromatic hydrocarbons (PAHs

• borylation of unsubstituted HBC. HBC was pulverized by a ball mill prior to use. First, we attempted the iridium catalyst and reagents that we have reported as the suitable C–H borylation conditions for warped nanographene: [Ir(OMe)cod]2, 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen), HBpin (Bpin: 4,4,5,5

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• -trimethoxybenzene in CH3CN. (b) Changes in the fluorescence spectra upon the addition of diphenyl disulfide in CH3CN. (c) Stern–Volmer quenching plot of iridium catalyst in the presence of 1,2,4-trimethoxybenzene and diphenyl disulfide. Kq (arene) = 318 ± 2.6 M−1 L and Kq (disulfide) = 36 ± 0.7 M−1 L. Black line

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• interestingly, when the reaction was performed using an aryl or alkylsulfonyl chloride, instead of trifluoromethanesulfonyl chloride, no extrusion of the SO2 moiety was observed, and the sulfonated products were recovered. The reaction mechanism involved excitation of the iridium catalyst under visible light to

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• ]. Recently Xiao et al. [94] has reported an acceptor-free oxidative dehydrogenation with a versatile iridium catalyst (Scheme 35). A variety of tetrahydroquinolines 93 were converted to the aromatic quinoline 94 using the iridium catalyst in 2,2,2-trifluoroethanol (TFE) at higher temperature. As an extension

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• carried out in the presence of an iridium catalyst and antimony hexafluoride (AgSbF6) under mild conditions. The starting chalcones were almost completely converted into 1-indanones 138–142 and isolated in very good yields. Our research group synthesized 3-aryl-1-indanones 148 and previously unknown 3

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• alkoxide species C. Reductive elimination of species C gave the product and regenerated the active iridium catalyst. Recently, Qiu and co-workers developed a novel chiral ligand L5 based on a chiral-bridged biphenyl backbone and successfully achieved the asymmetric addition of arylboronic acids to N

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• literature of an enantioselective insertion of an iridium carbenoid into C(sp3)–H bonds. Che and coworkers introduced the first porphyrin-based chiral iridium catalyst (−)-65 to insertion of carbenoids into C(sp3)–H bonds [52]. The reaction with 1,4-cyclohexadiene was promoted by 1 mol % of the catalyst at

• , ranging from 2.5:1 to >20:1, favoring the anti-product, in a complementary sense when compared to the results reported by Suematsu and Katsuki for iridium catalyst 61a (Table 8). Poor to excellent yields and high enantioselectivity were reported for the main product. The chiral porphyrin-based iridium

• group Ar1 (p-CH3Ph = 24 h; p-FPh, m-ClPh, m-BrPh = 10 min) and the enantioselectivity drops from 70–80% ee to less than 50% ee when Ar1 is m-ClPh or m-BrPh. In 2013, Davies, Blakey and coworkers reported a new iridium catalyst to perform a carbenoid insertion into the C(sp3)–H bond (Scheme 15) [54]. The

Iridium/N-heterocyclic carbene-catalyzed C–H borylation of arenes by diisopropylaminoborane

• Mamoru Tobisu,
• Takuya Igarashi and
• Naoto Chatani

Beilstein J. Org. Chem. 2016, 12, 654–661, doi:10.3762/bjoc.12.65

• ) system. Results and Discussion On the basis of a superior reactivity of indoles in several C–H borylation reactions [7][8][9], we initially examined the borylation of indole 2 with aminoborane 1g using an iridium catalyst under forcing conditions (140 °C, 15 h). Although all the attempts to isolate an

•  3, entry 5). Naphthalene also underwent borylation with 1g at the less hindered 2-position (Table 3, entry 6). Our protocol was performed on a gram scale without any difficulty using a lower loading of the iridium catalyst (Scheme 2, top). Using 1g as the boron source in C–H borylation reactions has

Visible-light-induced, Ir-catalyzed reactions of N-methyl-N-((trimethylsilyl)methyl)aniline with cyclic α,β-unsaturated carbonyl compounds

• Dominik Lenhart and
• Thorsten Bach

Beilstein J. Org. Chem. 2014, 10, 890–896, doi:10.3762/bjoc.10.86

• -aminomethyl radicals [43][44][45] to enones. N-Methyl-N-((trimethylsilyl)methyl)aniline (5) for example served as substrate for the alkylation of 2-cyclohexenone (6) employing iridium catalyst 7. When using the amine as the limiting reagent and an excess of enone (1.5 equiv) product 8 was obtained in 70

• reactions to other cyclic α,β-unsaturated carbonyl compounds. In particular, we were interested to see whether cyclization reactions as for product 4 would be observed when using α,β-unsaturated lactones and lactams in combination with a silylated amine and an iridium catalyst. In this article, we provide

Aqueous reductive amination using a dendritic metal catalyst in a dialysis bag

• Jorgen S. Willemsen,
• Jan C. M. van Hest and
• Floris P. J. T. Rutjes

Beilstein J. Org. Chem. 2013, 9, 960–965, doi:10.3762/bjoc.9.110

• examples, we decided to design a metallodendrimer that would show catalytic activity in a cascade process while compartmentalized under aqueous conditions. To this end, an iridium catalyst was selected that was known to be suitable for reductive amination in an aqueous environment. We showed that by

• catalyst can also be easily removed from the reaction mixture after the reaction has been completed (Figure 1). Results and Discussion To study this approach, we selected iridium catalyst 3, which has been previously successfully applied in aqueous reductive aminations [27]. The catalyst is based on

• related iridium complexes that are capable of performing transfer hydrogenation reactions, as has been documented by Fukuzumi et al. [28][29][30]. The water-soluble iridium catalyst 3 was prepared according to a procedure of Francis in high yield (Scheme 1) [27]. The starting material is [Cp*IrCl2]2 which

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

• Andrew Tigchelaar and
• William Tam

Beilstein J. Org. Chem. 2012, 8, 1765–1770, doi:10.3762/bjoc.8.201

• –94%). These results are the first examples of cycloadditions of alkynyl halides using an iridium catalyst. Keywords: alkynyl halide; cycloaddition; diene-tethered alkyne; iridium; transition-metal catalyst; Introduction Iridium complexes have been used as catalysts for a wide variety of reactions

• substrates with a 4-atom tether. Optimization of iridium-catalyst for [4 + 2] cycloaddition of alkynyl bromide 1a. Optimization of solvent and temperature for the [IrCl(cod)]2/dppe-catalyzed [4 + 2] cycloaddition of 1a. [IrCl(cod)]2/dppe-catalyzed [4 + 2] cycloadditions of various alkynyl halides

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• chain at C5 through chelation. We chose Crabtree’s iridium catalyst ([Ir(cod)PCy3(py)]PF6) which has been reported to furnish excellent facial selectivities during directed hydrogenations of cyclic olefins [32][33][34]. Hydrogenation of acetate 16 in the presence of 11 mol % of Crabtree’s catalyst under

Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene

• Alexandre Pradal,
• Chung-Meng Chao,
• Patrick Y. Toullec and
• Véronique Michelet

Beilstein J. Org. Chem. 2011, 7, 1021–1029, doi:10.3762/bjoc.7.116

• chiral iridium catalyst [41] (Scheme 1, reaction 2). We and others recently pursued the improvement and development of this enantioselective process, by employing platinum [42][43][44], rhodium [45] or gold [46][47][48] complexes. Following our previous work with chiral gold catalysts [46], we report a

Iridium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes with secondary amine nucleophiles

• Dingqiao Yang,
• Ping Hu,
• Yuhua Long,
• Yujuan Wu,
• Heping Zeng,
• Hui Wang and
• Xiongjun Zuo

Beilstein J. Org. Chem. 2009, 5, No. 53, doi:10.3762/bjoc.5.53

• and 5 mol % bisphosphine ligand (S)-p-Tol-BINAP. The trans-configuration of 3f was confirmed by X-ray crystallography. Keywords: chiral bisphosphine ligand; iridium catalyst; oxabicyclic alkenes; ring-opening reaction; Introduction Substituted dihydronaphthalenes are important molecules with

• molecules with the dihydronaphthalene skeleton. Results and Discussion The ARO reaction involves many components of the chemical agents; we first attempted to optimize the ligand to iridium catalyst system (Scheme 1). In our initial experiments, we chose an achiral 1,1′-bis(diphenylphosphino)ferrocene (DPPF

• order of Firidium catalyst from chloride to iodide or bromide leads to improvements in