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

• . Subsequently, insertion of alkene 68 provides the cyclic Pd(II) intermediate 72 which undergoes β-hydride elimination to produce the desired product 69. In the same year, Ramana and Goriya [75] proposed an unexpected C-6 (C-2)-propenylation reaction of pyridine in the presence of allyl bromide (73) and a Ru

• catalyst using 2-arylpyridines (Scheme 15). Earlier reports described the propenylation took place on the ortho-position of the phenyl ring [76][77], whereas this group achieved the propenylation of the pyridine moiety. The authors screened different allyl halides and Ru complexes as catalysts. With the

Electrochemical hydrogenation of enones using a proton-exchange membrane reactor: selectivity and utility

• Koichi Mitsudo,
• Haruka Inoue,
• Yuta Niki,
• Eisuke Sato and
• Seiji Suga

Beilstein J. Org. Chem. 2022, 18, 1055–1061, doi:10.3762/bjoc.18.107

• ). Next, the effect of cathode catalysts was investigated (Table 3). With Ru catalyst, further reduction of the carbonyl group proceeded, and both 2a (32% yield) and 3a (14% yield) were obtained (Table 3, entry 2). With Rh catalyst, the conversion was up to 81%, while the yield of 2a was similar to that

• with Ru catalyst (Table 3, entry 3). Similarly, both 2a and 3a were obtained with Ir and Pt catalyst (Table 3, entries 4 and 5). In particular, 3a was obtained preferentially with the Ir catalyst. These results revealed that the cathode catalysts strongly affected the selectivity between 2a and 3a. Pd

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

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

• diene 49 involved cross-metathesis with an excess of methacrolein, catalyzed by 122, followed by a Wittig olefination. The union of the diene 49 with 1.8 equivalents of the vinyl tetrahydropyran 97 was achieved with the Ru catalyst 122. One recycle of the recovered starting material from this reaction

• afforded the fragment 125. The cross-metathesis of 125 with an excess of methacrolein in the presence of the Ru catalyst 122 gave the aldehyde 126. This coupling is analogous to Koide’s cross-metathesis of 121 (cf. Scheme 20). A modified Julia olefination of 126 with the anion generated from the sulfone 78

One-pot synthesis of isosorbide from cellulose or lignocellulosic biomass: a challenge?

• Isaline Bonnin,
• Raphaël Mereau,
• Thierry Tassaing and
• Karine De Oliveira Vigier

Beilstein J. Org. Chem. 2020, 16, 1713–1721, doi:10.3762/bjoc.16.143

• . The authors observed a deactivation of the Ru-catalyst in the presence of substrates containing lignin that was probably due to fouling and poisoning. Moreover, the presence of sulfuric acid could have been modified the Ru/C catalyst. With the increase of strong acid sites on the catalyst surface, the

• (5.0 wt % Ru, Ru nanoparticles (NPs): 0.9 nm) in 30 mL H2O after 1 h of reaction at 220 °C under 60 bar of H2. Trace amounts or even no isosorbide was obtained over microporous HZSM-5, NaY, and γ-Al2O3-supported Ru catalysts. A bifunctional Ru catalyst supported on mesoporous niobium phosphate with a

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• metathesis steps applying the second-generation Hoveyda–Grubbs Ru catalyst, while, unexpectedly, the second-generation Grubbs ruthenium catalyst was less active and gave rise to some side-products. (−)-Galanthamine An important alkaloid active in the treatment of mild to moderate Alzheimer's disease and

• (+)-3-epi-kempene-2 (14c). Importantly, the tandem metathesis of the dienyne precursor could also be performed in good yield (82%) with the Grubbs first-generation Ru catalyst (10 mol %). (+)-Lycoflexine alkaloid In 2010, Ramharter and Mulzer [83] prepared an intricate tricyclic intermediate useful for

• the total synthesis of the alkaloid (+)-lycoflexine (15). In this strategy, first a protected dienyne precursor was prepared that, by an enyne tandem ring-closing metathesis induced by the Grubbs second-generation Ru catalyst, produced a tricyclic diene in 52% yield. Next, a selective hydrogenation of

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

• -worker’s results [86], in 2015, Rueping and co-workers reported reoxidation reactions via visible photoredox catalysis [87]. In their study, they used photoredox catalyst 9 along with a Ru catalyst for ortho C–H functionalization of phenol derivatives, viz, ortho-(2-pyridyl)phenols (Pyr, Scheme 2

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

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• fluorescent in the presence of ethylene, thus leading to the release of 101 from the Ru-catalyst (Scheme 22). Live cell experiments with Chlamydomonas reinhardtii suggest that 20 µM of probe 102 in PBS buffer are sufficient to turn fluorescence on in cells flushed with exogenous ethylene or ethylene gas

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

• ] cyclotrimerization of the dialkyne 306 with variously disubstituted alkynes 307 performed on a solid phase TentaGel® resin (0.25 mmol/g) in the presence of Ru catalyst (Scheme 86). In case of 309–316, this reaction led to the formation of mixtures of two regioisomers. The examined regioisomeric ratios (a/b) were

Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation

• Michał Malik and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2016, 12, 2602–2608, doi:10.3762/bjoc.12.255

• 1,4-addition of vinylmagnesium bromide to sugar-derived cyclohexenone, followed by an aldol reaction with a derivative of but-3-enal. The obtained diene is then subjected to an assisted tandem catalytic sequence: ring-closing metathesis with the subsequent reuse of the Ru-catalyst in the syn

• Snapper [41][42]. Both groups described a methodology, in which the ring-closing metathesis (RCM) reaction is followed by the reuse of the Ru catalyst in the syn-dihydroxylation step. In our recent papers [43][44], we extended this concise and effective approach to the synthesis of bicyclic iminosugars

• not successful, since it yielded a complicated, inseparable mixture of diastereoisomers instead of one major product. Both diolefins 25 and 26 were subjected to the ring-closing metathesis (Scheme 7) with the Hoveyda–Grubbs II generation catalyst (5 mol %), followed by the reuse of the Ru catalyst in

Effective immobilisation of a metathesis catalyst bearing an ammonium-tagged NHC ligand on various solid supports

• Krzysztof Skowerski,
• Jacek Białecki,
• Stefan J. Czarnocki,
• Karolina Żukowska and
• Karol Grela

Beilstein J. Org. Chem. 2016, 12, 5–15, doi:10.3762/bjoc.12.2

• resulted system. In parallel work, the recyclability of an immobilised Ru-catalyst bearing quaternary ammonium-tagged NHC ligand was described. Selected classical and heterogeneous ruthenium complexes. Applications of NHC ammonium-tagged catalysts. Influence of temperature and concentration on RCM of 9

Synthesis and structures of ruthenium–NHC complexes and their catalysis in hydrogen transfer reaction

• Chao Chen,
• Chunxin Lu,
• Qing Zheng,
• Shengliang Ni,
• Min Zhang and
• Wanzhi Chen

Beilstein J. Org. Chem. 2015, 11, 1786–1795, doi:10.3762/bjoc.11.194

• of acetophenone, we further explored their catalytic potential in the reduction of other aromatic and aliphatic ketones. The reaction conditions are similar as those described in the transfer hydrogenation of acetophenone and 0.1 mol % of Ru catalyst is utilized. The obtained results are given in

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• the pyridine derivative 220 with an excess amount of the 5-hexenylmagnesium bromide in the presence of a catalytic amount of iron complex 18 as the precatalyst provides the dialkylation product 221 (75%). The treatment of the hydrochloride solution of 221 with Ru catalyst 17 in a dilute CH2Cl2

• treated with the Ru catalyst to deliver the metacyclophane in a regioselective manner. The ratio of para, meta, and orthocyclophane formation depends on the chain length of the diynes employed (Scheme 44). Tanaka and co-workers [178] demonstrated a useful approach to strained dioxa[7]paracyclophane 276 by

Direct C–H trifluoromethylation of di- and trisubstituted alkenes by photoredox catalysis

• Ren Tomita,
• Yusuke Yasu,
• Takashi Koike and
• Munetaka Akita

Beilstein J. Org. Chem. 2014, 10, 1099–1106, doi:10.3762/bjoc.10.108

• (bpy)3](PF6)2, also promoted the present reaction, providing the product 3a in an 85% NMR yield (Table 1, entry 8). The Ru catalyst is less expensive than the Ir catalyst; thus, we chose the Ru photocatalyst for the experiments onward. Notably, product 3a was obtained neither in the dark nor in the

• illustrated in Scheme 5. According to our previous photocatalytic trifluoromethylation [37][38][39][40][41], the trifluoromethyl radical (·CF3) is generated from an one-electron-reduction of electrophilic Umemoto’s reagent 1a by the photoactivated Ru catalyst, *[Ru(bpy)3]2+. ·CF3 reacts with alkene 2 to give

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• under a variety of conditions (Table 4). In the absence of a Ru catalyst, a kinetic resolution occurs and 26 and the resolved alcohol (2S)-21 were isolated in similar yields (Table 4, entry 1). Upon addition of Shvo’s catalyst C, only minor amounts of the desired acetate 26 and no resolved alcohol were

Continuous preparation of carbon-nanotube-supported platinum catalysts in a flow reactor directly heated by electric current

• Alicja Schlange,
• Antonio Rodolfo dos Santos,
• Ulrich Kunz and
• Thomas Turek

Beilstein J. Org. Chem. 2011, 7, 1412–1420, doi:10.3762/bjoc.7.165

• tests were carried out at 80 °C with pure oxygen as an oxidant (200 mL·min−1). 1 M MeOH solution at a flow rate of 5 mL·min−1 was supplied to the anode. The cathode layer was prepared using synthesized Pt/CNT catalysts, while the anode was fabricated using commercial Pt/Ru catalyst from BASF (40 wt % Pt

Olefin metathesis in nano-sized systems

• Didier Astruc,
• Abdou K. Diallo,
• Sylvain Gatard,
• Liyuan Liang,
• Cátia Ornelas,
• Victor Martinez,
• Denise Méry and
• Jaime Ruiz

Beilstein J. Org. Chem. 2011, 7, 94–103, doi:10.3762/bjoc.7.13

• shown here to be excellent reactors achieving the goal of decreasing the catalytic amount when water is used as solvent. The success of using water as a reaction medium, even without co-solvent, is important in avoiding polluting organic solvents. Moreover, a very low Ru catalyst loading is possible in

The intriguing modeling of cis–trans selectivity in ruthenium-catalyzed olefin metathesis

• Naeimeh Bahri-Laleh,
• Raffaele Credendino and
• Luigi Cavallo

Beilstein J. Org. Chem. 2011, 7, 40–45, doi:10.3762/bjoc.7.7

• metathesis; Ru-catalyst; Introduction Olefin metathesis is among the most versatile tools when C=C double bonds must be manipulated. For this reaction Ru-based catalysts of various generations are particularly attractive due to their high tolerance for other functional groups [1][2][3][4]. Among the most

• biased towards the formation of the trans-isomer. For this reason, we decided to investigate computationally the cis–trans selectivity in the CM of the simplest terminal olefin, i.e., propene, to yield either cis- and trans-2-butene with the well characterized 2nd generation Ru-catalyst based on the

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• would result in polymers with ill-defined repeat units, which would also affect the physical properties of the polymer. Noteworthy, under ADMET conditions, the first-generation Ru-catalyst was found not to isomerize olefins [27]. In model studies carried out with simple olefins, Wagener and co-workers

Development of dynamic kinetic resolution on large scale for (±)-1-phenylethylamine

• Lisa K. Thalén and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2010, 6, 823–829, doi:10.3762/bjoc.6.97

• -phenylethyl)acetamide (3) in good yield and high ee when alkyl methoxyacetates were used as acyl donors compared to when isopropyl acetate was used as the acyl donor. The catalyst loading could be decreased to 1.25 mol % Ru-catalyst 4 and 10 mg CALB per mmol 1 when alkyl methoxyacetates were used as the acyl

• were observed when the reaction mixture was concentrated from 0.06 M to 0.13 M (Table 1, entries 1 and 7, respectively). The parameters were then changed concurrently to find a balance between the rate of acylation and racemization at lower catalyst loadings. When the Ru-catalyst loading was decreased

• to 2 mol % and the reaction concentration was increased to 0.25 M, the amide 2 could be obtained in 77% yield with 99% ee (Table 2, entry 1). When the Ru-catalyst loading was further decreased to 1 mol%, and the amount of CALB or acyl donor was increased, a decrease in the enantioselectivity of the

Large- scale ruthenium- and enzyme- catalyzed dynamic kinetic resolution of (rac)-1-phenylethanol

• Krisztián Bogár,
• Belén Martín-Matute and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2007, 3, No. 50, doi:10.1186/1860-5397-3-50

• larger scale and the results are summarized in Table 1. On a 10 mmol-scale, 1 mol% of Ru-catalyst 1 can be used to achieve 90% yield of acetate 3 (99% ee) after 18 h at room temperature (entry 1). A decrease of the catalyst loading to 0.5 mol% afforded 87% of enantiopure acetate, although a longer

• high efficiency of the latter reaction suggests that the racemization catalyst loading can be further decreased, and that an increased reaction temperature may facilitate this decrease. Indeed, a DKR reaction at 70°C on a 1 mol-scale employing only 0.05 mol% Ru-catalyst in a more concentrated reaction

• . Under optimized reaction conditions, DKR of 1-phenylethanol (2) was performed delivering 159 g (97% yield) of enantiomerically pure (R)-1-phenylethanol acetate (3) in a short reaction time (20 h) using 0.05 mol% of Ru-catalyst 1, and small amounts of enzyme. The employed heterogeneous biocatalyst