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

• cosmetics [147]. The catalyst could be recycled, however, with reduced performance due to Pt nanoparticle oxidation. 3.1.2 Polybutadiene (PBD): Partial depolymerisation of 1,4-PBD (cis, trans, Mw 1800–500000 g⋅mol−1) was achieved by an unconventional tandem ring-opening–ring-closing metathesis route

Menthyl esterification allows chiral resolution for the synthesis of artificial glutamate analogs

• Kenji Morokuma,
• Shuntaro Tsukamoto,
• Kyosuke Mori,
• Kei Miyako,
• Ryuichi Sakai,
• Raku Irie and
• Masato Oikawa

Beilstein J. Org. Chem. 2021, 17, 540–550, doi:10.3762/bjoc.17.48

• ). Enantiospecific synthesis of TKM-38 For the enantiospecific synthesis of TKM-38, which uniquely bears an eight-membered azacycle as the ring C, we explored 1) the amino-protecting group and 2) the conditions for the cyclization of the medium-sized ring by ring-closing metathesis (RCM). Finally, the established

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• with a cleavage of the distal C–C bond. The reaction proceeded regioselectively and in high yields. There was no difference observed between cis and trans-isomers in terms of the reactivity and yields. The resultant dienes 129 were used in ring-closing metathesis reactions to furnish gem

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• chemical ecology of Adalia bipunctata and the recent methodologies to obtain adaline (1), euphococcinine (2), and N-methyleuphococcinine (3). Keywords: 9-azabicyclo[3.3.1]nonane; Coccinelid beetles; dipolar cycloaddition; homotropane; ring-closing metathesis; Introduction Coccinellid beetles contain a

• (−)-48, in 88% yield, as a single diastereoisomer. Then, (−)-48 was treated with trimethyl orthoformate to provide formamide (−)-49, being converted to cis-2,6-dialkenylformamide (−)-50 by treatment with the Lindlar catalyst. (−)-50 underwent a ring-closing metathesis efficiently in the presence of the

• (−)-79a and (−)-79b, which were oxidized to enone (−)-80. The enone (−)-80 was subjected to ring-closing metathesis with Grubbs second-generation catalyst resulting in cyclic enone (−)-81 in 74% yield. (−)-81 was treated with phenylselenol to generate selenide 82 in high yield. The ozonolysis of 82 was

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• 60% yield (74% yield, brsm). A two-step synthesis from 127 produced diene 128, which was subjected to ring-closing metathesis and subsequent Dess–Martin oxidation to give 129 in 63% yield over two steps. Tetracycle 130, which was prepared from 129 in one step, was converted to lycojaponicumin C (18

• and AIBN to a refluxing solution of cyclopropane 155 afforded 156 in 38% yield. It was subjected to cleavage of the Boc group followed by N-allylation to give 157 in 73% yield over two steps. A ring-closing metathesis of freshly prepared 157 was effected by the second generation Hoveyda–Grubbs (HG II

• of aldehyde 163 and isoprene (164) with Ni(acac)2 and diethylzinc [78] and then Dess–Martin oxidation gave a diene (not shown, 94% yield over two steps), which was subjected to ring-closing metathesis to give enone 165 in 85% yield. Isomerization of the freshly prepared 165 to more stable α,β

A novel and robust heterogeneous Cu catalyst using modified lignosulfonate as support for the synthesis of nitrogen-containing heterocycles

• Bingbing Lai,
• Meng Ye,
• Ping Liu,
• Minghao Li,
• Rongxian Bai and
• Yanlong Gu

Beilstein J. Org. Chem. 2020, 16, 2888–2902, doi:10.3762/bjoc.16.238

• , ring-closing, metathesis, cycloadditions, radical reactions and microwave-assisted reactions [38][39][40]. In this work, we attempt to develop a greener, simpler, more efficient and recyclable system to synthesize arylpyridine derivatives. Initially, the reaction of acetophenone (5a) and 1,3

Ring-closing metathesis of prochiral oxaenediynes to racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans

• Viola Kolaříková,
• Markéta Rybáčková,
• Martin Svoboda and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2020, 16, 2757–2768, doi:10.3762/bjoc.16.226

• enantioselective enyne metathesis yielding chiral building blocks for compounds with potential biological activity, e.g., norsalvinorin or cacospongionolide B. Keywords: Diels–Alder reaction; enediyne; enyne metathesis; ring-closing metathesis; ruthenium precatalyst; Introduction Among the plethora of metathetic

• reactions of unsaturated compounds, e.g., alkene and enyne cross metathesis (CM [1] and EYCM [2][3][4]), alkene and enyne ring-closing metathesis (RCM and RCEYM) [5][6], ring-opening metathetic polymerization (ROMP) [7], etc., the CM and RCM are the most popular in organic synthesis [8]. Furthermore, the

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• catalyst 15 to yield the trimerized products 12 (syn) and 13 (anti) in respectable yields (Scheme 2). The alkene-bridge exchange of 12 (syn) was accomplished by tandem ring-opening and ring-closing metathesis (ROM–RCM) in the presence of Grubbs’ first generation (G-I) catalyst to generate a C3-symmetric

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

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

• generation of the mixed acetal 113 (Scheme 18) [33]. A ring-closing metathesis gave an inseparable mixture of the dihydropyranyl ethers 114a and 14b, which could be equilibrated under acidic conditions (114b/114a > 20:1). A standard functional group manipulation afforded the vinyldihydropyran-2-one (−)-115

• hydrogenation over Pt2O and then low-temperature DIBAL reduction afforded the all-cis tetrasubstituted tetrahydropyran 27. In Koide et al.’s synthesis, the unsaturated lactone 29 was prepared via the Wittig methenylation of 24, followed by aminal hydrolysis, methallylation of the 2° alcohol 28, and ring-closing

• metathesis using Grubbs’ 2nd generation catalyst (G-II, Scheme 3) [13]. Replacing the N-Boc protecting group with an N-tosyl group and allylic oxidation gave 30. The introduction of the allyl group at C-11 made use of the Kishi protocol [22] of the allyl-Grignard addition, followed by an ionic reduction. The

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• butadiene derivative and P-reagent used [36][48][49][50]. However, the long reaction times, as well as the moderate or low yields make this approach less appealing. More recent syntheses of the phospholene oxides involve either a ring-closing metathesis [35][51][52][53][54], or a double Arbuzov reaction of

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

• of known, in vivo effective substances but also for designing chemically modified analogs as valid alternatives for further therapeutic agents. Keywords: bioactive compounds; enyne metathesis; ring-closing metathesis; ruthenium catalysts; tandem reactions; Introduction Alkene and alkyne metathesis

• peroxide groups in the corresponding artemisinin analog was eventually achieved by applying further oxidation. In a similar way to the above Oguri protocol, Li et al. prepared nanolobatolide (2), a potent neuroprotective agent, by successfully applying a tandem ring-closing metathesis of dienynes and

• synthesized starting from ʟ-methionine. The subsequent enyne ring-closing metathesis in the presence of the Grubbs first-generation catalyst (5 mol %) afforded a pyrrolidine derivative in 76% yield (Scheme 12). This pyrrolidine was converted into a pyrrolo-1,4-benzodiazepinone bearing a vinyl side group

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• alcohol due to decomposition. Nonetheless, several products could be transformed into molecules of greater complexity. For example, cyclopropanation could be achieved to give 269. Additionally, TBS protection of 268 followed by ring closing metathesis (RCM) led to the interesting 6-membered silacycle 270

Rapid, two-pot procedure for the synthesis of dihydropyridinones; total synthesis of aza-goniothalamin

• Thomas J. Cogswell,
• Craig S. Donald and
• Rodolfo Marquez

Beilstein J. Org. Chem. 2020, 16, 135–139, doi:10.3762/bjoc.16.15

• Zealand 10.3762/bjoc.16.15 Abstract A fast, protecting-group-free synthesis of dihydropyridinones has been developed. Starting from commercially available aldehydes, a novel one-pot amidoallylation gave access to diene compounds in good yields. Ring-closing metathesis conditions were then employed to

• produce the target dihydropyridinones efficiently and in high yields. Keywords: amidoallylation; aza-goniothalamin; dihydropyridinones; protecting-group-free; ring-closing metathesis; two-pot procedure; Introduction Six-membered nitrogen heterocycles are prevalent in many naturally occurring and

• and co-workers, who developed a one-pot, three-component reaction to produce protected homoallylic amines 4 (Scheme 1) [19]. It was reasoned that adaptation of the Veenstra protocol would allow us to introduce a second alkene unit during the same process, thus generating a ring-closing metathesis

Progress in metathesis chemistry

• Karol Grela and
• Anna Kajetanowicz

Beilstein J. Org. Chem. 2019, 15, 2765–2766, doi:10.3762/bjoc.15.267

• catalysts work and decompose, how macrocycles are formed in ring-closing metathesis, etc. Representative examples of these directions have been the subject of the current, third thematic issue on Olefin Metathesis, including highly educative reviews on tandem olefin metathesis–Suzuki–Miyaura cross coupling

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• developed for the synthesis of bile acid-based macrocycles, using macrolactamization, ring-closing metathesis and Ugi-multicomponent macrocyclization. Developing more efficacious and economical methods for the construction of these macrocycles is still in demand due to the disadvantages of the

• -derived tris(crown ether) host (eTC) via a dynamic covalent chemistry approach involving triple threading and a Grubbs-catalyzed ring-closing metathesis [68]. 1H NMR titration experiments have been used for the identification of co-conformations of the four related stable states of 19. The authors have

Synthesis and biological evaluation of truncated derivatives of abyssomicin C as antibacterial agents

• Leticia Monjas,
• Peter Fodran,
• Johanna Kollback,
• Carlo Cassani,
• Thomas Olsson,
• Maja Genheden,
• D. G. Joakim Larsson and
• Carl-Johan Wallentin

Beilstein J. Org. Chem. 2019, 15, 1468–1474, doi:10.3762/bjoc.15.147

• carbonyl addition reaction between aldehyde 3 and the tetronate derivatives 4 and 5, followed by a ring-closing metathesis (Scheme 1). Since both enantiomers of AbC have similar activity [25], we pursued racemic synthesis of the targeted compounds. We synthesized the common building block 3 in six steps

• ). Treatment of 18 and 19 with Hoveyda–Grubbs second generation catalyst in refluxing 1,2-dichloroethane afforded the ring-closing metathesis products 20 and 21 in 62% and 45% yield, respectively. Deprotection of the TBDMS group using tetrabutylammonium fluoride followed by final Dess–Martin oxidation gave the

Remarkable effect of alkynyl substituents on the fluorescence properties of a BN-phenanthrene

• Alberto Abengózar,
• David Sucunza,
• Patricia García-García and
• Juan J. Vaquero

Beilstein J. Org. Chem. 2019, 15, 1257–1261, doi:10.3762/bjoc.15.122

• vinyl trifluoroborate. The optimal conditions to obtain 3 were found to be heating at 110 °C for 72 h. Lower temperatures and/or shorter times led to incomplete conversions in the borylative cyclization of 2. Ring-closing metathesis of 3 proceeded efficiently in the presence of 10 mol % of the second

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• by NMR, ESIMS, and X-ray crystallography. The utility of this chemistry is further demonstrated by the tests of the novel catalysts (up to 10−2 mol %) in different metathesis reactions such as cross metathesis (CM), ring-closing metathesis (RCM) and ring-opening cross metathesis (ROCM). Keywords: CM

• ; cross metathesis; Hoveyda–Grubbs catalyst; olefin metathesis; RCM; ring-closing metathesis; ring-opening cross metathesis; ROCM; ruthenium metathesis catalyst; styrene; 2-vinylbenzylamine; Introduction Ruthenium-catalysed olefin metathesis reactions have been playing an important role in various fields

• ][9][10][11][12], including most popular recent books [13][14]. Obviously, the application of various catalysts is required to achieve the best results in each of the many directions of metathesis reactions such as cross metathesis – CM, ring-opening metathesis – ROM, ring-closing metathesis – RCM

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• Suberites japonicus (Thiele) has been synthesized only once, with relay ring-closing metathesis being the key step [9]. Characteristically, seragamides A–E exhibit a L-threonine unit at the C-terminus of the peptide moiety. There is a considerable body of work on the synthesis of the C12 polyketide section

• -closing metathesis [9][21][22]. The C3–C4 bond has been assembled by 1,2-cuprate rearrangement [23]. Iterative construction of the polyketide from smaller building blocks has been achieved by Matteson homologation [24], that was also applied to the synthesis of the related polyketide section of lagunamide

• . In most cases, the C2–C3 bond was formed by Ireland-, Johnson-, or Eschenmoser–Claisen rearrangement [10][11][12][13][14][15][16][17]. Alternatively, Evans methodology has been used [18][19][20]. The central C4–C5 double bond has also been constructed by Wittig reaction, cross metathesis, and ring

Design of indole- and MCR-based macrocycles as p53-MDM2 antagonists

• Constantinos G. Neochoritis,
• Maryam Kazemi Miraki,
• Eman M. M. Abdelraheem,
• Ewa Surmiak,
• Tryfon Zarganes-Tzitzikas,
• Beata Łabuzek,
• Tad A. Holak and
• Alexander Dömling

Beilstein J. Org. Chem. 2019, 15, 513–520, doi:10.3762/bjoc.15.45

• -pot procedure with one purification step), much better yields, no need of expensive catalysts as in ring-closing metathesis (RCM) reaction and higher complexity/diversity on the macrocyclic ring, e.g., insertion of heteroatoms that could improve the ADMET properties (Scheme 1) [4]. Results and

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

• metathesis (ADMET), ring-closing metathesis (RCM), ring-opening metathesis (ROM), and cross-metathesis (CM). Catalytic cycle for metathesis proposed by Chauvin. First aqueous ROMP reactions catalyzed by ruthenium(III) salts. Degradation pathway of first generation Grubbs catalyst (G-I) in methanol. Synthesis

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• ]. The higher reactivity of COE in ROMP is the reason for the formation of long octenylene sequences. The MCO was obtained by ring-closing metathesis and contained easily cleavable ester linkages. It gave the possibility to сut the multiblock copolymer into pieces under alkaline conditions in order to

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• bidentate ligands investigated by a number of research groups [5]. The pyridinyl alcohol found its way to the Grubbs-type complexes from research by Van Der Schaaf and co-workers on the Schrock-type analogues [6][7]. Grubbs 1-type complexes 3a–f (Figure 2) were used to catalyse the ring-closing metathesis

Ammonium-tagged ruthenium-based catalysts for olefin metathesis in aqueous media under ultrasound and microwave irradiation

• Łukasz Gułajski,
• Andrzej Tracz,
• Katarzyna Urbaniak,
• Stefan J. Czarnocki,
• Michał Bieniek and
• Tomasz K. Olszewski

Beilstein J. Org. Chem. 2019, 15, 160–166, doi:10.3762/bjoc.15.16

• ionic tag attached to the benzylidene ligand, with that of catalyst 1a, bearing an ionic tag placed on the N-heterocyclic carbene (NHC) fragment. As model reactions we have selected the ring-closing metathesis (RCM) of the water-soluble substrate 6, the homometathesis of alcohol 8, and more challenging

Synthesis of a tubugi-1-toxin conjugate by a modulizable disulfide linker system with a neuropeptide Y analogue showing selectivity for hY1R-overexpressing tumor cells

• Rainer Kufka,
• Robert Rennert,
• Goran N. Kaluđerović,
• Lutz Weber,
• Wolfgang Richter and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2019, 15, 96–105, doi:10.3762/bjoc.15.11

• ][55][56]. In a single step, the Ugi reaction permits the introduction of different functionalities which may be followed with additional modifications on the side chain (e.g., via ring-closing metathesis or Click reaction) [53]. For tubugi conjugates we learned that alkyl amide bonds and several types