Recent advances in synthetic approaches for bioactive cinnamic acid derivatives

• Betty A. Kustiana,
• Galuh Widiyarti and
• Teni Ernawati

Beilstein J. Org. Chem. 2025, 21, 1031–1086, doi:10.3762/bjoc.21.85

• to 429 (Scheme 88A) [149]. On the other hand, Novikov and co-workers (2019) utilized Rh(II) to catalyze the [2 + 1 + 1] assembly of spiro β-lactams 431–434 from diazocarbonyl compound 430 and azirines via Rh carbenoid 435 followed by aziridine ring-opening (436 and 437) (Scheme 88B) [150]. Lv and co

Entry to new spiroheterocycles via tandem Rh(II)-catalyzed O–H insertion/base-promoted cyclization involving diazoarylidene succinimides

• Alexander Yanovich,
• Anastasia Vepreva,
• Ksenia Malkova,
• Grigory Kantin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2024, 20, 561–569, doi:10.3762/bjoc.20.48

• (namely furan-2(5H)-ones, tetrahydrofurans and pyrans spiro-conjugated with the succinimide ring) has been developed. The protocol consists of Rh(II)-catalyzed insertion of heterocyclic carbenes derived from diazoarylidene succinimides (DAS) into the O–H bond of propiolic/allenic acids or brominated

• extension of this methodology. This study is aimed at the development of convenient protocols for the synthesis of new spiroheterocycles via tandem Rh(II)-catalyzed OH insertion/base-promoted cyclization using DAS and various OH substrates containing an activated multiple bond (propiolic and allenic acids

• earlier and the synthetic methodology investigated in this work. An initial example on Rh(II)-catalyzed O–H insertion/base-promoted cyclization involving diazo compound 1a. Tandem Rh2(esp)2-catalyzed O–H insertion/base-promoted cyclization involving DAS 1 and various propiolic acids; PMP = 4-methoxyphenyl

N-Boc-α-diazo glutarimide as efficient reagent for assembling N-heterocycle-glutarimide diads via Rh(II)-catalyzed N–H insertion reaction

• Grigory Kantin,
• Pavel Golubev,
• Alexander Sapegin,
• Alexander Bunev and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2023, 19, 1841–1848, doi:10.3762/bjoc.19.136

• , including both aromatic and saturated NH-substrates. This yields structures that are appealing for generating cereblon ubiquitin-ligase ligands and for potential use in crafting PROTAC molecules. Keywords: CRBN ligands; diazocarbonyl compounds; N–H insertion reaction; N-heterocycles; Rh(II)-catalysis

• simplified the process of isolating compound 5, as compared to the prior publication [26], and notably increased its stability. Furthermore, the solubility of the new diazo reagent in non-polar solvents, particularly DCM, was significantly improved, leading to a beneficial impact on the course of Rh(II

• decreased (62% (NMR) vs 69% (isolated)). When Rh2(TFA)4 (1 mol %) was used, a reversal of the ratio of 6a/9a insertion products (1:2) was observed in the test reaction, although the total yield estimated by NMR was only 32%. Thus, in the series of tested Rh(II) catalysts Rh2(esp)2 is the most successful

A novel spirocyclic scaffold accessed via tandem Claisen rearrangement/intramolecular oxa-Michael addition

• Anastasia Vepreva,
• Alexander Yanovich,
• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1649–1655, doi:10.3762/bjoc.18.177

• ][11][12][13][14] constitutes a distinctly worthy undertaking which may as well influence the outlook of the novel medicines discovered and developed in the future. Recently, we described a novel Rh(II)-catalyzed spirocyclizations involving diazo arylidene succinimide (DAS, such as 1a) with

• impetus from the synthetic point of view. Specifically, we wanted to see if Rh(II)-catalyzed insertion of DAS-derived carbenes could be performed into the O–H bond of phenols and if the resulting phenoxy-substituted succinimides 5 could also undergo a Claisen rearrangement. The products of the latter (6

• phenolic O–H bond, the Claisen rearrangement and the base-catalyzed cyclization to the spirocyclic product, we experimented with attempts to perform all three steps in a one-pot format. This gave inferior results in terms of product yield and purity. The best result was obtained by performing the Rh(II

Unusual highly diastereoselective Rh(II)-catalyzed dimerization of 3-diazo-2-arylidenesuccinimides provides access to a new dibenzazulene scaffold

• Anastasia Vepreva,
• Alexander S. Bunev,
• Andrey Yu. Kudinov,
• Grigory Kantin,
• Mikhail Krasavin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2022, 18, 533–538, doi:10.3762/bjoc.18.55

• method for the preparation of this class of compounds [2] and showed that DAS can undergo Rh(II)-catalyzed insertion reactions into the heteroatom–H bonds [3]. In 2020, it was shown that under Rh(II) catalysis, DAS can enter insertion reactions into the C–O bond of ethers [4], a rare transformation for

• compounds (aldehydes and ketones) enable to obtain the products of formal [5 + 2] cycloaddition reactions ‒ 2-benzazepines [8] and 2-benzoxepines [9][10]. When studying the Rh(II)-catalyzed reaction of DAS with ketones [10], we attempted to involve poorly reactive fluorenone in the reaction. To our surprise

• DAS component 1 on the outcome of the Rh(II)-catalyzed decomposition. The results obtained clearly demonstrate that the nature of the substituent at the nitrogen atom in the DAS molecule has a minor effect: the substrates bearing both donor- and acceptor-substituted aryl groups form dimers 2 in high

Synthesis of N-perfluoroalkyl-3,4-disubstituted pyrroles by rhodium-catalyzed transannulation of N-fluoroalkyl-1,2,3-triazoles with terminal alkynes

• Olga Bakhanovich,
• Viktor Khutorianskyi,
• Vladimir Motornov and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 504–510, doi:10.3762/bjoc.17.44

• , conveniently prepared by [3 + 2] cycloadditions of terminal alkynes with sulfonyl azides, have been used as the precursors to N-sulfonylindoles by transition-metal-catalyzed transannulation reactions. In the presence of Rh(II) or Ni(0) catalysts the triazole ring-opening takes place and intermediate highly

Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin

• Sara Peeters,
• Linn Neerbye Berntsen,
• Pål Rongved and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2019, 15, 2156–2160, doi:10.3762/bjoc.15.212

• : catalysis; cyclopropanation; indole; norfloxacin quinoline; quinolone; Rh(II); ring expansion; Introduction The development and use of metal carbenes occupy a central part in the field of the C–H functionalization [1]. Among the metal carbenes, the transient Rh carbenes, usually made by Rh-catalyzed

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

• alkenes and alkynes [74]. Rh(I)/Rh(II)/Rh(III) catalysts have been used in asymmetric syntheses of chiral heterocycles that have been effectively reviewed by Chen and Xu in 2017 [75]. The role of ruthenium in synthetic chemistry Over the past decade, Ru and its complexes were used as a catalyst in various

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• presence of 2-indobenzoic acid anion. Recently, Shi’s group developed the first ring expansion of MCPs 63 with a nitrogen atom to furnish azetidines 64 (Scheme 14) [82]. The author proposed that Rh(II) had an effective impact on the reactions and could improve the reaction yields. Unfortunately, the MCPs

• -tethered alkylidenecyclopropanes). Rh(II)-catalyzed oxidative radical ring-opening and cyclization of MCPs. Ag(I)-catalyzed oxidative radical amination/ring-opening/cyclization of MCPs derivatives. Heating-promoted radical ring-opening and cyclization of MCP derivatives (arylvinylidenecyclopropanes) with

Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes

• Jury J. Medvedev,
• Ilya V. Efimov,
• Yuri M. Shafran,
• Vitaliy V. Suslonov,
• Vasiliy A. Bakulev and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2017, 13, 2569–2576, doi:10.3762/bjoc.13.253

• Str., 620002, Ekaterinburg, Russia Center for X-ray Diffraction Studies, St-Petersburg State University, 26 University pr., 198504, Saint-Petersburg, Russia 10.3762/bjoc.13.253 Abstract A new approach towards the synthesis of multisubstituted thiophenes is elaborated based on Rh(II)-catalyzed domino

• the same molecule. The main objective of our current research was to study Rh(II)-catalyzed reactions of diazocarbonyl compounds with α-cyanothioacetamides, bearing both thioamide and cyano groups in their structure. Based on the known literature findings [36][37][38] one might expect that a catalytic

• diazomalonate, which is unusual for Rh(II)-catalyzed reactions of this diazo compound [26]. Application of more active catalysts like dirhodium tetraoctanoate or tetrapivalate makes it possible to reduce the reaction time at reflux in benzene to 2 h (Table 1, entries 3 and 4). In the case of dirhodium

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• ]. The diazo compounds could be collected as solution in dichloromethane at the output of the flow system, and obtained sufficiently pure for further use without requiring handling or isolation. Further mixing of solutions containing diazo derivatives to a solution containing a Rh(II) catalyst, and

Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products

• Valerij A. Nikolaev,
• Jury J. Medvedev,
• Olesia S. Galkina,
• Ksenia V. Azarova and
• Christoph Schneider

Beilstein J. Org. Chem. 2016, 12, 1904–1910, doi:10.3762/bjoc.12.180

• .12.180 Abstract Rh(II)-сatalyzed reactions of aroyldiazomethanes, diazoketoesters and diazodiketones with α,β-unsaturated δ-aminoesters, in contrast to reactions of diazomalonates and other diazoesters, give rise to the Wolff rearrangement and/or oxidative cleavage of the initially formed N–H-insertion

• products. These oxidation processes are mediated by Rh(II) catalysts possessing perfluorinated ligands. The formation of pyrrolidine structures, characteristic for catalytic reactions of diazoesters, was not observed in these processes at all. Keywords: diazo compounds; N–H-insertion; oxidation cleavage

• colleagues showed that similar reactions can be extended to compounds with triple bonds and allene fragments [14]. Recently we have shown that the catalytic decomposition of diazomalonates and other diazoesters using Rh(II)- and Cu(II)-complexes in the presence of α,β-unsaturated δ-(N-aryl)amino esters 1

On the cause of low thermal stability of ethyl halodiazoacetates

• Magnus Mortén,
• Martin Hennum and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2016, 12, 1590–1597, doi:10.3762/bjoc.12.155

• briefly studied the thermal, non-catalytic cyclopropanation of styrenes and compared the results to the analogous Rh(II)-catalyzed reactions. Keywords: carbenes; catalysis; cyclopropanation; halo diazoacetates; half-lives; thermal stability; Introduction The chemistry of diazo compounds has fascinated

• halodiazoacetates 2a–c (Scheme 1) from 1 and studied their reactivity in Rh(II)-catalyzed reactions [11]. In the presence of Rh(II) catalysts the halodiazoacetates extrude N2 and form the corresponding Rh–carbenes which undergo typical carbenoid reactions such as cyclopropanation [11], cyclopropanation–ring

• expansion [12], and C–H insertion and Si–H insertion reactions [13]. Under Rh(II)-catalysis conditions, 2b extrudes N2 much faster than 1 (15 s vs 8 min to 50% conversion) [14]. The higher reaction rate implies a lower turnover limiting barrier in the catalytic cycle with 2b compared to 1. This example made

Recent advances in C(sp³)–H bond functionalization via metal–carbene insertions

• Bo Wang,
• Di Qiu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2016, 12, 796–804, doi:10.3762/bjoc.12.78

• over the decades [1][2][3][4][5][6][7][8]. Mechanistically, the C(sp3)–H bond insertion reaction is considered to follow a concerted reaction pathway with a three-center two electron transition state (Scheme 1). Since late transition metals, typically Rh(II) complexes, are most commonly employed as the

• methyl ethers [21]. The use of 2,2,2-trichloroethyl aryldiazoacetates, in combination with sterically crowded chiral Rh(II) catalysts Rh2(R-BPCP)4, enhances the site-selectivity and the enantioselectivity of the reaction. Interestingly, the C–H bonds of a methyl group show high reactivity over the

• judicious combination of reagents and catalysts. Rh(II)-catalyzed site-selective and enantioselective intramolecular carbene insertion into the C–H bond at the α-position of a tertiary amine have been previously established by Davies and co-workers [22][23][24]. Recently, this methodology has been used in

Synthesis of quinoline-3-carboxylates by a Rh(II)-catalyzed cyclopropanation-ring expansion reaction of indoles with halodiazoacetates

• Magnus Mortén,
• Martin Hennum and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2015, 11, 1944–1949, doi:10.3762/bjoc.11.210

• halodiazoacetates. The formation of the quinoline structure is probably the result of a cyclopropanation at the 2- and 3-positions of the indole followed by ring-opening of the cyclopropane and elimination of H–X. Keywords: catalysis; cyclopropanation; indole; quinoline; Rh(II); ring expansion; Introduction The

• byproducts [20][21]. In comparison, the Rh(II)-catalyzed reaction between indole and ethyl halodiazoacetates took place under mild reaction conditions and gave ethyl quinoline-3-carboxylate in good to high yields. Based on our promising results from the initial experiments we decided to investigate the scope

• with 2-methylindole and Br-EDA in the absence of the Rh(II) catalyst and found that the thermal reaction gave the corresponding quinoline structure, but the conversion of 2-methylindole was still low and the yield was poor (~15%, measured by internal standard, 1H NMR). The yields of ethyl quinoline 3

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

• -acylation of cis-4-hydroxy-D-proline (albeit not the hydrochloride salt in this case) has also been employed as a key step in the preparation of ligands for new chiral Rh(II) catalysts (Scheme 14) [74]. Extension of chemoselective acidic O-acylation reactions to other substrates and comparison with other

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

• Nikolai V. Rostovskii,
• Mikhail S. Novikov,
• Alexander F. Khlebnikov,
• Galina L. Starova and
• Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

• , Universitetskaya nab. 7–9, 199034 St. Petersburg, Russia 10.3762/bjoc.11.35 Abstract Strained azirinium ylides derived from 2H-azirines and α-diazoketones under Rh(II)-catalysis can undergo either irreversible ring opening across the N–C2 bond to 2-azabuta-1,3-dienes that further cyclize to 2H-1,4-oxazines or

• reversibly undergo a 1,5-cyclization to dihydroazireno[2,1-b]oxazoles. Dihydroazireno[2,1-b]oxazoles derived from 3-aryl-2H-azirines and 3-diazoacetylacetone or ethyl diazoacetoacetate are able to cycloadd to acetyl(methyl)ketene generated from 3-diazoacetylacetone under Rh(II) catalysis to give 4,6-dioxa-1

• . In the work reported herein we studied Rh(II)-catalyzed reactions of alkyl-, aryl-, and hetaryl-substituted 2Н-azirines with α-diazo-α-phenylacetone (2a), α-diazo-4-chloroacetophenone (2b), and 3-diazoacetylacetone (2c). A new type of transformation of azirinium ylides, specifically 1,5-cyclization

Isoxazolium N-ylides and 1-oxa-5-azahexa-1,3,5-trienes on the way from isoxazoles to 2H-1,3-oxazines

• Alexander F. Khlebnikov,
• Mikhail S. Novikov,
• Yelizaveta G. Gorbunova,
• Ekaterina E. Galenko,
• Kirill I. Mikhailov,
• Viktoriia V. Pakalnis and
• Margarita S. Avdontceva

Beilstein J. Org. Chem. 2014, 10, 1896–1905, doi:10.3762/bjoc.10.197

• obtained in 14% yield when heated under reflux in CH2Cl2 and with the use of dirhodium tetraoctanoate instead of Rh2(OAc)4 as a catalyst. This unsatisfactory result prompted us to test a carbene instead of a Rh(II) carbenoid, since it has been found [23] that carbenes can be successfully generated by

• a significantly greater influence on the stabilization than the corresponding chalcone system. Thus, there is a good correspondence between the theoretical and experimental results, both of which support that Rh(II)-catalyzed reactions of diazo compounds with isoxazoles do not involve the formation

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• Rh(II)-catalyzed C–H and OH insertion reactions (Scheme 4). The preparation of both enantiomeric furanose building blocks commenced with the Rh2(OAc)4-catalyzed OH insertion of 39, respectively 40 into the α-diazo-β-ketoester 40. A tandem [3,3]/[1,2]-rearrangement cascade, followed by reductive

Parallel and four-step synthesis of natural-product-inspired scaffolds through modular assembly and divergent cyclization

• Hiroki Oguri,
• Haruki Mizoguchi,
• Hideaki Oikawa,
• Aki Ishiyama,
• Masato Iwatsuki,
• Kazuhiko Otoguro and
• Satoshi Ōmura

Beilstein J. Org. Chem. 2012, 8, 930–940, doi:10.3762/bjoc.8.105

• precursors 36–38 based on the unified three-step protocol. The Rh(II)-catalyzed tandem cyclization–cycloaddition of the branched precursors 36–38 exclusively occurred at module 3. The cyclized products 40–42, having the indole group at module 4 intact, were obtained in good yields. It is worth noting that

• module 3, we then synthesized precursors 45 and 46 with a terminal alkyne and a furan ring, respectively, by using amine building blocks 43 and 44 according to the reported procedure [22]. The Rh(II)-catalyzed tandem reactions of 45 and 46 again proceeded at module 3 to produce cyclized products 47 and

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• , yielding either a cyclic sulfonium ylide or a six-ring carbonyl ylide. In fact, it has been found that Rh(II)-catalyzed dediazoniation of α-diazo-β-ketoesters with γ-phthalimido [18][19] or related [20] substituents gives rise to cyclic carbonyl ylides, which were trapped by intermolecular cycloaddition

• reactions. In this paper, we report that the formation of sulfonium as well as carbonyl ylides are indeed competing pathways in the Rh(II)-catalyzed dediazoniation of phthaloyl-protected γ-amino-α-diazo-β-ketoesters derived from methionine, S-benzylcysteine, and S-allylcysteine. Results and Discussion

• , reflux, 2 h; 2. N2=CHCO2Et (2 equiv), rt, 4 days. Rh(II)-catalysed carbenoid reactions of diazoesters 8a,b. Endo transition state for [3 + 3]-dimerisation of carbonyl ylide 14. Rh(II)-catalysed carbenoid reactions of diazoester 8c. Tandem cyclisation/intermolecular cycloaddition of diazoester 8a