Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• would afford the [2 + 2] adduct. Hydroruthenation of the allene produces 103 which can either undergo reductive elimination to afford the cyclopropanated bicyclic alkene or undergo a [2 + 2] cycloreversion to generate the Ru–carbene 104. The Ru–carbene 104 can rearrange to 100 through a 1,3-migration 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

• catalyzed by Grubbs 2nd generation Ru-carbene, these intermediates then led to the tricyclic sesquiterpenoid-like scaffolds I–VIII (Scheme 4), as suitable precursors for the synthesis of artemisinin and its analogs (1a–c). After selecting the optimal tricyclic intermediate, the installation of the bridged

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

• semicrystalline and amorphous samples of partly hydrogenated PBD underwent ethenolysis in the presence of the Ru-carbene catalyst. This depolymerization procedure resulted in the formation of telechelics with both end vinylated. Then, the ethylene atmosphere was replaced with argon and an additional amount of

• the MCM conditions enables one to obtain copolymers with a controllable average block length ranging from the initial homopolymer length to a few monomer units. Important data on the kinetics of MCM between PNB and PCOE mediated by Gr1 were obtained by combining in situ NMR studies of the Ru-carbene

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

• suitable reagent, a “chemical trigger” [69]. In the case of the RCM/allylic oxidation sequence tert-butyl hydroperoxide is added after completion of the metathesis reaction, which most likely induces a conversion of the metathesis active Ru–carbene species to a Ru(IV)–oxo species. The latter are known to

Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

• Ritabrata Datta and
• Subrata Ghosh

Beilstein J. Org. Chem. 2018, 14, 2708–2714, doi:10.3762/bjoc.14.248

• diene. Thus unlike metathesis of 7a, metathesis of its acetate analogue 7b occurred through a domino ROM–RCEYM process. Addition of the Ru-carbene 10 arising from ring opening of norbornene unit in 7b could add to the acetylenic unit of another molecule of 7b leading to copolymerization. However, this

• process generally does not take place under such low molar concentration of the substrate [38][39][40][41][42][43]. We also did not isolate any copolymerization product. This may be attributed to the much faster rate of addition of the Ru-carbene 10 to the yne unit intramolecularly resulting in ring

Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

• Markus Menke,
• Pardha Saradhi Peram,
• Iris Starnberger,
• Walter Hödl,
• Gregory F.M. Jongsma,
• David C. Blackburn,
• Mark-Oliver Rödel,
• Miguel Vences and
• Stefan Schulz

Beilstein J. Org. Chem. 2016, 12, 2731–2738, doi:10.3762/bjoc.12.269

• ), requiring more than 10 steps each. RCM can shorten the synthesis remarkably, but requires careful selection of the RCM catalyst to control the double bond configuration. For example, Fürstner and Langemann obtained rac-1 in 31:69 (E/Z)-mixture using a Ru-carbene type catalyst similar to a Grubbs I catalyst

New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand

• Agnieszka Hryniewicka,
• Szymon Suchodolski,
• Agnieszka Wojtkielewicz,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 2795–2804, doi:10.3762/bjoc.11.300

• compounds even at 0 °C. It was also examined in more demanding systems such as conjugated dienes and polyenes. The catalyst is stable, storable and easy to purify. Keywords: chromane derivatives; metathesis catalyst; nitrogen heterocycles; olefin metathesis; Ru-carbene; Introduction Olefin metathesis is

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• % yield [51]. The regioselective formation of 240 may be attributed to the facile formation of a Ru–carbene intermediate where the metal participates on the side opposite to that of the methyl ester and thereby minimizing the steric crowding between ruthenium and carbonyl oxygen of an ester functionality

• various Ru–carbene complexes in one-pot sequence generate various complex targets. It is an atom economic process producing a wide range of polycyclic compounds containing highly demanding structures efficiently. Starting with relatively simple substrates, the final compounds obtained by the RRM process

Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

• Yulia I. Denisova,
• Maria L. Gringolts,
• Alexander S. Peregudov,
• Liya B. Krentsel,
• Ekaterina A. Litmanovich,
• Arkadiy D. Litmanovich,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2015, 11, 1796–1808, doi:10.3762/bjoc.11.195

• we estimate and compare the formation and decay rates of Ru–carbene complexes bound to PCOE and PNB. Then we proceed to the investigation of PCOE/PNB/Gr-1 mixtures, where we combine in situ 1H NMR measurements of the concentrations of Ru–carbene complexes with ex situ 13C NMR measurements of

• corresponding experimental NMR data plotted in Figure 6. Qualitatively, it means that the cleavage of a polymeric double C=C bond is about an order of magnitude more probable in the reaction with a polymer-bound Ru-carbene than with a [Ru]=CHPh carbene. Further kinetic studies on that issue are needed to get

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

• ruthenium–NHC complexes presented above are stabilized by strong Ru–carbene bonds and contain 2–4 easily dissociating acetonitrile molecules, and are thus ideal catalysts. We tested their catalytic activities for transfer hydrogenation of ketones. Firstly, acetophenone was selected as the model substrate to

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• ring closure (89%) under milder conditions (CH2Cl2): all attempts to employ the 1st-generation Grubbs catalyst 2 in RCM failed, supposedly because of an unfavourable steric environment during generation of the Ru–carbene species from 109, as compared to 98 (distinct N-protective groups). Cyclic sulfate

The catalytic performance of Ru–NHC alkylidene complexes: PCy₃ versus pyridine as the dissociating ligand

• Stefan Krehl,
• Diana Geißler,
• Sylvia Hauke,
• Oliver Kunz,
• Lucia Staude and
• Bernd Schmidt

Beilstein J. Org. Chem. 2010, 6, 1188–1198, doi:10.3762/bjoc.6.136

• -based [6] catalysts have experienced extensive further developments and improvements. Due to their robustness towards air and moisture, and their comparatively low sensitivity towards functional groups, Ru-carbene complexes have attracted a particularly high degree of attention and “numerous variations

Cross-metathesis of allylcarboranes with O-allylcyclodextrins

• Ivan Šnajdr,
• Zbyněk Janoušek,
• Jindřich Jindřich and
• Martin Kotora

Beilstein J. Org. Chem. 2010, 6, 1099–1105, doi:10.3762/bjoc.6.126

• reactions, which has also been observed in other metathetical reactions with alkenylcyclodextrins derivatives [27] and can be explained by several factors [28]. Firstly, by a chelation of the intermediate Ru-carbene complex to the oxygen atoms of the cyclodextrin which results in a conformationally rigid