Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• transfer one or more groups from one group 13 element to another, through σ-bond metathesis; where boron is both of the group 13 elements, this is termed transborylation. These redox-neutral processes are increasingly being used to render traditionally stoichiometric group 13-mediated processes catalytic

• by σ-bond metathesis, a redox neutral process (Scheme 1). Stoichiometric group 13 exchange reactions are key to the synthesis of group 13 reagents including in organoboron chemistry [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], and more recently with aluminium [29][30][31

• [58]. The alkyne 1 and dialkylborane reacted to give an alkenylborane 2. Transborylation with HBpin gave the alkenyl boronic ester 3 and regenerated the catalyst, HBR2. Isotopic labelling (H10Bpin) confirmed B–C(sp2)/B–H transborylation proceeded by σ-bond metathesis, and not ligand exchange. Using

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

• construction of the 8-membered ring from an appropriate cyclopentane precursor. The proposed strategies include metathesis, Nozaki–Hiyama–Kishi (NHK) cyclization, Pd-mediated cyclization, radical cyclization, Pauson–Khand reaction, Lewis acid-promoted cyclization, rearrangement, cycloaddition and biocatalysis

• precursor. The proposed strategies include metathesis, Nozaki–Hiyama–Kishi (NHK) cyclization, Pd-mediated cyclization, radical cyclization (including SmI2), Pauson–Khand reaction, Lewis acid-promoted cyclization, rearrangement, cycloaddition, and biocatalysis. In particular, the purpose will focus on the

• following criteria: position/stage of the key cyclooctane ring formation in the synthesis plan, the selectivity, and the opportunity for late-stage functionalization. Review 1 Metathesis: ring-closing metathesis and related methods The metathesis reaction, first discovered by serendipity in the 1950s, has

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• chlorides 6 initially gives N-acyliminium salts 8, which are activated upon treatment with AgOTf resulting in an anion metathesis of Cl− with OTf−. This activation is proposed to facilitate the desired aza-Nazarov reaction to afford the cyclized intermediate 9, which is stabilized by the trimethylsilyl (TMS

Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• purifications can be an easier and more effective alternative. An efficient method to homogeneously scavenge a ruthenium complex used in a metathesis reaction was described by Grela and co-workers on a 60 g scale [89]. The use of heterogeneous scavenger columns in flow mode is sometimes criticized. If the final

• produced as byproduct in the metathesis reaction. Some subsequent publications include the Pd-complex removal after a Suzuki coupling [126], a Heck catalyst retention with reverse boiling-point-order solvent exchange [127], and a membrane for recovery of the photocatalyst TBADT (tetrabutylammonium

B–N/B–H Transborylation: borane-catalysed nitrile hydroboration

• Filip Meger,
• Alexander C. W. Kwok,
• Franziska Gilch,
• Dominic R. Willcox,
• Alex J. Hendy,
• Kieran Nicholson,
• Andrew D. Bage,
• Thomas Langer,
• Thomas A. Hunt and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2022, 18, 1332–1337, doi:10.3762/bjoc.18.138

• transborylation (a σ-bond metathesis turnover method) has been used for borane-catalysed reductions of N-heteroarenes [28][29], and the borane-catalysed cyanation of enones [30]. Applying B–N/B–H transborylation to the hydroboration of nitriles would enable the development of a borane-catalysed hydroboration of

Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells

• Merve Karaman,
• Abhishek Kumar Gupta,
• Subeesh Madayanad Suresh,
• Tomas Matulaitis,
• Lorenzo Mardegan,
• Daniel Tordera,
• Henk J. Bolink,
• Sen Wu,
• Stuart Warriner,
• Ifor D. Samuel and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2022, 18, 1311–1321, doi:10.3762/bjoc.18.136

• -dibromobutane in moderate yield, followed by a second alkylation step with 1-methylimidazole in very good yield. DiKTa-OBuIm was isolated as its hexafluorophosphate salt following anion metathesis with NH4PF6. DiKTa-DPA-OBuIm was obtained also in three steps at 35% overall yield from compound 4 using a similar

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• ]. The α-ketoester 41 was accessible from amide 38, which in turn was obtained from allylic alcohol 37. Oxidation and Horner–Wadsworth–Emmons reaction with phosphonate 39 delivered the silyl enol ether 40, which was deprotected and cyclized via a Grubbs metathesis to α-ketoester 41. Subsequent

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

• -oxides 56a in 23% and 93 in 63% yields, respectively, showing the limited scope of the synthetic method (Scheme 17) [39]. Ring-closing metathesis (RCM) is an efficient strategy for the construction of cyclic compounds via the formation of a C=C bond [40][41], which can be reduced to the C–C bond. 2

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• -closing metathesis [3][4]. It is well described that metathesis reactions can be significantly accelerated in flow, as the boiling point of the solvent employed can be exceeded using back pressure regulators (BPRs) and formed gases (e.g., ethylene) can be easily removed employing tube-in-tube reactors [11

• ]. Therefore, Roberge, Fogg, and co-workers investigated the advantages of continuously stirred tank reactors (CSTR) and tube reactors in comparison to the corresponding batch reaction for the ring-closing metathesis of diene 58, producing macrocyclic olefin 60 (Scheme 14) [52]. Although, macrocycle 60 is not

• 20 min at 80 °C using 1 mol % of catalyst 59 [52]. Due to the fact that ethylene formed in the ring-closing metathesis can result in the formation of unstable ruthenium methylidene species, causing degeneration of the metathesis catalyst, the continuous removal of ethylene from the reaction mixture

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• equivalents of the acyclic precursor (S)-46 were preorganized by a Ca template and catenation was achieved by two-fold ring closing metathesis. This reaction yielded catenane (S,S)-47 (14% yield, see Figure 12) together with the non-interlocked macrocycle (S,S)-48 (22% yield, for the structure see Figure 13

A resorcin[4]arene hexameric capsule as a supramolecular catalyst in elimination and isomerization reactions

• Tommaso Lorenzetto,
• Fabrizio Fabris and
• Alessandro Scarso

Beilstein J. Org. Chem. 2022, 18, 337–349, doi:10.3762/bjoc.18.38

• synthesis of sesquiterpene natural product derivatives [38][39] and the carbonyl olefin metathesis leading to 2,5-dihydropyrroles [40]. Herein we present our investigation on the ability of the hexameric capsule 16 to act as a supramolecular self-assembled organocatalyst for a series of unimolecular

Synthesis and late stage modifications of Cyl derivatives

• Phil Servatius and
• Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

• compound, we decided to use the Cyl-1 amino acid backbone and introduce a double unsaturated side chain (Scheme 1). In principle, selective modifications at the two different double bonds (internal and terminal) should be possible. Ring-closing metathesis (RCM) should generate an allylglycine unit, which

• the removal of metathesis catalysts is the formation of Ru-DMSO complexes, which do not eluate from a silica column [56]. This allowed us to remove at least the Ru contamination, but we were unable to subject 12 to further modifications such as cross metathesis or thiol-ene click reactions due to poor

Earth-abundant 3d transition metals on the rise in catalysis

• Nikolaos Kaplaneris and
• Lutz Ackermann

Beilstein J. Org. Chem. 2022, 18, 86–88, doi:10.3762/bjoc.18.8

• syntheses, crop protection or medicinal chemistry. Particularly, cross-coupling reactions [1], as well as alkene and alkyne metathesis [2][3], have considerably changed the art of molecular synthesis, with a major impact on neighboring disciplines, such as molecular biology or materials sciences. Despite of

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• stapling and the most prominent methodology was developed by the groups of Grubbs and Verdine using ring-closing metathesis (RCM) [4][5][6]. The optimised protocol for these so-called hydrocarbon-stapled peptides uses α-methyl-, α-alkenylglycines in a distance of i, i + 3/i + 4 for one helix turn or i, i

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• -hydrogen shift and σ-bond metathesis with hydrosilane to give the silylated pyrrole product 63 and the LCuH catalyst 57. In addition, the intermediate 58 might go through isomerization to form imine intermediate 64, which undergoes intramolecular cyclization to provide the minor regioisomer 67 (inner cycle

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• –Smith cyclopropanation; Hyptis brevipes Poit; ring-closing metathesis; Introduction Hyptis brevipes Poit. is an invasive plant species belonging to the mint family Lamiaceae [1][2][3][4]. This plant has been reported to originate from tropical America but is now distributed broadly in other tropical

• followed by esterification with 3-butenoic acid (37) under Steglich conditions (Scheme 3). The resulting product 38 was isolated in 86% yield. A subsequent ring-closing metathesis reaction and DBU-assisted double bond migration then furnished the anticipated structure 39. The PMB functionality was removed

• acid (17) (Scheme 4). The β-hydroxy moiety in 44 can be installed via Sharpless dihydroxylation of the silyl enol ether derived from ketone 45. The 5,6-dihydro-α-pyrone group in ketone 45 is envisaged from protected diol 46 by the sequence of Mitsunobu esterification, ring-closing metathesis, and base

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• with a reaction yield ranging from 66% to 91% (Scheme 4). Finally, for some of the dyes, a metathesis reaction was carried out with sodium tetraphenylborate. Indeed, all dyes were obtained as iodine salts so that a counterion exchange could be carried out. Using this strategy, four “soft” salts could

• exposure to a laser diode at 785 nm (0.9 W/cm2), thickness = 1.4 mm. The irradiation starts at t = 10s. B) FTIR spectra before and after irradiation. Investigated NIR dyes. Other used chemicals. Synthetic routes to compounds Ca, Cb, and CNa. Synthetic routes to CI1, CI3, CI4, and CI6–CI9. The metathesis

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• Abstract This work presents an examination of the selective functionalization of norbornadiene through nitrile oxide 1,3-dipolar cycloaddition/ring-opening metathesis (ROM)/cross-metathesis (CM) protocols. Functionalization of commercially available norbornadiene provided novel bicyclic scaffolds with

• the CM transformations with the goal of exploring substrate and steric effects, catalyst influence and chemodifferentiation of the olefin bonds furnishing the corresponding functionalized, fluorine-containing isoxazoline derivatives. Keywords: functionalization; metathesis; nitrile oxide

• ; organofluorine chemistry; selectivity; Introduction Olefin metathesis is considered to be a powerful synthetic tool for the creation of olefin bonds [1]. Several types of metathesis reactions, such as ring-opening metathesis (ROM), cross-metathesis (CM), ring-closing metathesis (RCM) or ring-opening/cross

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• sequential modifications [30], photocyclization of divinylterphenyl derivatives [31], tandem radical cyclization of (Z,Z)-1,4-bis(2-iodostyryl)benzene derivatives [32], and ring-closing olefin metathesis of tetravinylterphenyls [33] as the best-known synthetic routes. Herein, we have classified the synthetic

• published in 2018, de Koning and co-workers reported a new methodology to synthesize the benzo[a]anthracene skeleton of angucycline derivatives 146 by using a multistep strategy based on Suzuki–Miyaura, isomerization, and ring-closing metathesis reactions (Scheme 33) [67]. The commercially available 2

• metathesis strategy to synthesize benz[a]anthracenes. Green synthesis of oxa-aza-benzo[a]anthracene and oxa-aza-phenanthrene derivatives. Triple benzannulation of substituted naphtalene via a 1,3,6-naphthotriyne synthetic equivalent. Zinc iodide-catalyzed Diels–Alder reactions with 1,3-dienes and aroyl

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• , several products were submitted to a subsequent metathesis mediated by Grubbs-II catalyst and a further palladium-catalyzed C=C reduction and DG-removal process, from which the desired macrocyclic peptides were obtained in good to excellent yields (Scheme 35C). Recently, again Ackermann and co-workers

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• -closing metathesis (RCM), Clauson–Kaas and Ullmann-type coupling reactions as key steps. Moreover, we have also assembled some other interesting heterocyclic systems possessing oxazole, imidazole, benzimidazole, and benzoxazole in the framework of truxene. Additionally, the preliminary photophysical

• properties (absorption and emission) for these versatile systems has been revealed. Keywords: Clauson–Kaas reaction; heterocycles; ring-closing metathesis; truxene; Ullmann-type coupling; Van Leusen reaction; Introduction The two-dimensional phenylene-based π-conjugated star-shaped architectures has

• metathesis, Ullmann-type coupling, Clauson–Kaas, and Van Leusen reactions as crucial transformations. Synthetic Strategy Basically, our endeavor toward the synthesis of truxene-based systems has been rooted in the development of new synthetic methodologies to assemble diverse polycyclic as well as

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

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• number of classical methodologies have been used for their synthesis, in which the key step is the generation of the six-membered ring, including the aldol reaction, the reductive amination, Mannich reaction, ring closing metathesis, Diels–Alder reaction with imines as dienophiles, aza-Prins cyclization

• products were obtained after four additional steps: cross-metathesis of allylated compounds 120 with methyl vinyl ketone, reduction of conjugated C=C double bond, removal of the sulfinyl group under acidic conditions, and final stereoselective reduction of the imine formed by intramolecular cyclization

• subsequent steps, including ring-closing metathesis [133], (−)-cermizine B (171) and (+)-serratezomine E (172) were obtained 57% and 72% yield, respectively (Scheme 43) [134][135]. Cyclizations involving a position in the attacking nucleophile Isosolenopsin (177) and solenopsin (178) are two isomeric

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• metathesis (RCM) [16], halo etherification [17], reductive etherification [18][19], and metal-mediated cyclization [20][21], etc. are the most frequent strategies utilized for THP ring construction (Scheme 1). Amongst all, the Prins reaction has proven as a powerful technique in the stereoselective synthesis