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

• alcohols, followed by base-promoted cyclization to afford the target spirocyclic compounds in good to high yields. Keywords: diazoarylidene succinimides; intramolecular cyclization; rhodium(II) carbene O–H insertion; spirocycles; Introduction Spirocyclic motifs have emerged as auspicious frameworks for

• this protocol for spirocyclization and spiroheterocycle formation. The first step of the synthesis, the insertion of rhodium carbene into the O–H bond of 3-bromopropanol, was carried out under standard conditions in the presence of 0.05 mol % Rh2(esp)2 in dry DCM. 1H NMR spectroscopy was used to

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• , tweezers 36 bearing pyrene fluorescent groups and using either rhodium(I) or copper(I) complexes as switching units were reported [79]. Cu(I), which avoids the luminescence quenching effect of Rh(I), requires pyridine as an ancillary ligand to complex the metal center and open the tweezers. The

• higher activity and enantioselectivity due to the preorganization of the Cr(III) catalytic centers enabling bimetallic catalysis compared to the more flexible arrangement of the salen in the open form. The tweezers could be opened by breaking the thioether–rhodium bond with a combination of Cl− and CO

• dissymmetric [Rh(P,O)(P,S)] complex. This rearrangement allows access to tweezers with two different arms with two types of weak sites of different reactivities. This HRI reaction was first used to access simple dissymmetric rhodium(I) tweezers such as 38 with different aromatic arms [82], 39 with Zn/Mg

(E,Z)-1,1,1,4,4,4-Hexafluorobut-2-enes: hydrofluoroolefins halogenation/dehydrohalogenation cascade to reach new fluorinated allene

• Nataliia V. Kirij,
• Andrey A. Filatov,
• Yurii L. Yagupolskii,
• Sheng Peng and
• Lee Sprague

Beilstein J. Org. Chem. 2024, 20, 452–459, doi:10.3762/bjoc.20.40

• defluorosilylation product was obtained [11]. In a related study of the hydrosilylation reaction of olefins 1a,b, it was shown that, depending on the catalyst used, platinum or rhodium compounds, along with the products of the addition of silane to the double bond, the elimination of the fluorine atom occurs with

Unveiling the regioselectivity of rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reactions for open-cage C₇₀ production

• Cristina Castanyer,
• Anna Pla-Quintana,
• Anna Roglans,
• Albert Artigas and
• Miquel Solà

Beilstein J. Org. Chem. 2024, 20, 272–279, doi:10.3762/bjoc.20.28

• holds significant promise for applications in the fields of medicinal chemistry, materials science, and photovoltaics. In this study, we investigate the regioselectivity of the rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reactions between diynes and C70 as a novel procedure for generating C70 bis

• opening. Keywords: cycloadditions; DFT calculations; [70]fullerene; open-cage fullerenes; rhodium; Introduction The discovery of C60 (buckminsterfullerene) in 1985 [1] initiated the search for possible technological applications of fullerenes. Nowadays, applications for these carbon-based molecules have

• study, we have explored the regioselectivity of the rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reaction between two different diynes and C70 with the objective of producing C70 bis(fulleroids). Mixtures of α- and β-site isomers were obtained, with the α-adduct being the major product of the reaction

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

• . However, this does not show much advantage over Rh2(esp)2 (0.18 mol %), which gave a preparative yield of 18%. It is important to note that despite the higher cost, the rhodium catalyst offers milder reaction conditions. In the case of some electron-rich substrates, in addition to N–H insertion products 6

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• predominantly earth-abundant materials. The recycling of NADH analogues has been carried out using precious metal complexes, such as [CpRh(bpy)(H2O)]2+ [47]. This rhodium complex was adhered to a photoelectrode in a photoelectrochemical cell which also contained a second photoelectrode functionalized with a set

• of enzymes [47]. The enzymes reduce carbon dioxide to methanol and consumed NADH which was then recycled at the photoelectrode functionalized with the rhodium complex. The overall electron donor in this work was water which makes it an excellent example of in-situ recycling. Kuk et al. also noted

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• their rhodium- and copper-catalyzed reactions (Scheme 2c) [116]. These results were in stark contrast to those observed for the ylide’s diazo counterparts, which did not react without a catalyst, and which gave the opposite diastereoselectivity with copper and rhodium. Inspired by ionic pathways

• -substituted iodoarene-derived iodonium ylides for improved solubility and stability [5][6][141]. ortho-Iodoanisole-derived ylide 39 was subject to a rhodium-catalyzed cyclopropanation reaction with styrene, and the results were compared with Charette’s 2009 work on 31 (Scheme 15) [142]. While both ylides were

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

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

• % yield. Further, Shi and co-workers reported the rhodium-catalyzed directed C–H olefination of pyridines using different directing groups in 2013 [88] (Scheme 20a) and 2014 [89] (Scheme 20c), respectively. In the former study, under optimized conditions of [RhCp*Cl2]2 (5 mol %), AgSbF6 (20 mol %) in DCE

• , displaying broad substrate scope and high yields (Scheme 20c). Based on literature reports and experimental studies, a possible mechanism (Scheme 20d) was proposed in which coordination of the DG 102 to the rhodium cationic species followed by ortho-metalation and migratory insertion of 103 into the Rh–C

• pyridine directing group 170 with rhodium providing a five-membered rhodacyclic intermediate I which further forms the aryl–rhodium(III) complex II by reaction with 171. Subsequently, this intermediate undergoes reductive elimination from the rhodium(III) center to furnish the desired ortho-C–H-arylated

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• synthesis of enantiomerically enriched cyclobutanes 77 [52]. Their strategy employed a three-component process in which tert-butyl (E)-2-diazo-5-arylpent-4-enoates 74 were treated with the chiral rhodium catalyst C1 to provide enantiomerically enriched bicyclobutanes 75. These highly strained compounds then

• Phebox-based rhodium complex (C3) to catalyze the tandem conjugate addition of a terminal alkene followed by reacting the bicyclic dienol silyl ether intermediate with Michael acceptors in a one-pot procedure (Scheme 50) [92]. The bridged cyclic products 196a,b, formed by a double Michael addition

• cyclization (Scheme 51A) [93]. The reaction starts with the coordination of the Rh catalyst to the propargyl alcohol 198. In the presence of a base, the rhodium–alkynyl reagent is generated with the concomitant extrusion of benzophenone. Finally, the alkynylation of the enone is followed by the cyclization

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

• sketched in red, with newly formed cyclic structures being highlighted. Review Earth-abundant metals Among the transition metal used in organic synthesis, the late transition metals like rhodium, palladium, and iridium have taken center stage when it comes to methodology development. Although these late

• phenanthridinones produced, the authors were able to quickly afford novel fagaronine 117j and nitidine 117k derivatives. Rhodium-catalyzed reactions In 2002, the Lautens laboratory reported a tandem cyclization of arylboronate esters 118 with a variety of bicyclic alkenes 15 using a water-soluble Rh-catalytic

• previously been a challenging transformation due to the propensity of these systems to produce non-cyclized hydroarylation products due to an unproductive rhodium 1,4-migration on heteroaromatic moieties. The use of benzothiophene, benzofurans, and benzopyrrole boronate esters in this investigation prevented

Transition-metal-catalyzed C–H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

• Louis Monsigny,
• Floriane Doche and
• Tatiana Besset

Beilstein J. Org. Chem. 2023, 19, 448–473, doi:10.3762/bjoc.19.35

• polysubstituted derivative 21g was also functionalized in high yield (71%). Pleasingly, other metals have been also successfully applied for the trifluoromethylthiolation of aromatic derivatives by C(sp2)–H bond activation such as Rh(III) and Co(III)-based catalysts as depicted below. Rhodium catalysis: In 2015

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

• allowed the functionalization for each natural product. Their general method consisted in using an intramolecular Pauson–Khand reaction catalyzed by a rhodium complex from an allene-yne substrate to build the eight-membered ring, which was quite challenging. Starting from commercial (R)-limonene (51), Li

• rhodium-based catalysts and 5% of [Rh(CO)2Cl]2 were found to be the best catalyst loading (28% yield). The addition of a silver additive, to make the reaction quicker and to remove a CO ligand, appeared to be useless in this case, with no reaction, and the use of 50% dppp as ligand allowed the formation

Practical synthesis of isocoumarins via Rh(III)-catalyzed C–H activation/annulation cascade

• Qian-Ci Gao,
• Yi-Fei Li,
• Jun Xuan and
• Xiao-Qiang Hu

Beilstein J. Org. Chem. 2023, 19, 100–106, doi:10.3762/bjoc.19.10

• . The success of gram-scale reaction and diverse functionalization of isocoumarins demonstrated the synthetic utility of this protocol. Keywords: C–H activation; enaminone; iodonium ylide; isocoumarin; rhodium catalysis; Introduction Isocoumarins are an important structural motif in many naturally

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

• arylidene succinimides; intramolecular oxa-Michael addition; rhodium(II) carbene O–H insertion; spirocycles; Introduction Spirocycles undoubtedly occupy a special place in drug design [1] and, in general, spirocyclic compounds intended for the interrogation of biological targets have been associated with

• cyclohexanone (as well as other cyclic ketones) which delivered spiro-annulated 2-benzoxepines (such as 2a) along with a minor byproduct 3a identified by 1H NMR as the product of formal insertion of the rhodium(II) carbene species into the O–H bond of cyclohexanone enol form. This minor byproduct, on heating at

Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone

• Motoyuki Isoda,
• Kazuyuki Sato,
• Kenta Kameda,
• Kana Wakabayashi,
• Ryota Sato,
• Hideki Minami,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1642–1648, doi:10.3762/bjoc.18.176

• , Setsunan University, 45-1, Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan, Faculty of Pharmaceutical Sciences, Hiroshima International University, 5-1-1 Hirokoshingai, Kure, Hiroshima 737-0112, Japan 10.3762/bjoc.18.176 Abstract A rhodium-catalyzed intramolecular reductive aldol-type cyclization is

• structural component of the pyrrolizidine alkaloid monocrotaline. Keywords: β-hydroxylactone; intramolecular reductive aldol cyclization; necic acid lactone; rhodium catalyst; Introduction Carbon–carbon bond-forming reactions are among the most important reactions in the synthetic chemistry toolbox and the

• such as Co [19][20][21], Cu [22][23][24][25], and others [26][27][28][29][30][31][32] with hydrosilanes (R3Si-H) or hydrogen as the reductant. In this area, rhodium catalysis has received significant attention [33][34][35][36][37][38][39][40], and we have also reported reductive α-acylations, reductive

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

• -phenylphosphonamidates 240a (R’ = OEt) and diaryl-N-phenylphosphinamides 240b–d (R’ = Ar), respectively, with methyl acrylate (241) via the rhodium-catalyzed oxidative coupling and subsequent intramolecular aza-Michael addition. Methyl acrylate (241) could be replaced by various electron-deficient olefins 244, including

• ]azaphosphole 1-oxides from aryl/vinyl-N-phenylphosphonamidates and aryl-N-phenylphosphinamides with electron-withdrawing ethenes via the rhodium-catalyzed oxidative coupling and subsequent intramolecular aza-Michael addition. Synthesis of 1,3-dihydro-[1,2]azaphospholo[5,4-b]pyridine 2-oxides. Funding The

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• metal–ligand motifs often center about iridium, ruthenium, rhodium etc. [25], the dynamic ones are constructed using copper(I), zinc(II), cadmium(II), iron(II), palladium(II), etc. as metal ions due to their more rapid ligand exchange rates [24][25][26]. The strategies to prepare inert vs dynamic

• . Transition-metal catalysts play an important role for the development of intricate pharmaceutical drugs. Although transition-metal catalysts based on rhodium, cobalt, and palladium have been intensively studied, gold catalysis has received encouraging attention only recently [67][68]. Since selectivity of

• final catalyst. In the next step, a transition-metal-ion based catalyst was prepared in situ by addition of one equiv of [Rh(acac)(CO)2], which generated the monoligated rhodium complex. Finally, catalysis was carried out at 5 bar of H2/CO (1:1) that converted the [Rh(acac)(CO)2] complex into the active

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

• at the double bond underwent cyclization as the result of intramolecular interception of the rhodium carbene, which led to the formation of indolizine [6] or 2H-chromene [7] derivatives, respectively (Figure 1). At the same time, Rh2(esp)2-catalyzed reactions of DAS with nitriles and carbonyl

• analysis (see Supporting Information File 1). A plausible mechanism of the observed transformations of DAS (shown for 1a) is presented in Scheme 2. The initially formed rhodium carbene A undergoes 1,5-electrocyclization to form intermediate B which turns into indene C as the result of a 1,5-suprafacial

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

• unit (12, used in both enantiomeric forms) or two BINOL units (26) were used for the construction of the rotaxane. The subsequent rhodium-catalyzed polymerization gave the corresponding polymers 32 in high yields of 89–98%. Here, the BINOL-based macrocycle is localized at the ammonium functionality of

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• studied rhodium complexes as catalysts for the arylation and alkylation of benzo- and naphthoquinones [83]. They synthesized menadione (10) (Scheme 3) by reacting 1,4-naphthoquinone (1) with methylboronic acid in the presence of [Cp*RhCl2]2 as catalyst for 10 h, in 31% isolated yield. Later in 2019, Yang

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• hydrogenation reaction mediated by a supramolecular catalyst was reported by Raymond, Bergman and Toste in 2019 (Figure 7) [64]. In this example, the supramolecular catalyst was prepared in situ by mixing a rhodium complex with the Ga4L612− cage host G, which had a relatively larger size with pyrene-walled

• achieved with just the rhodium catalyst, by which in contrast, the fully hydrogenated product was obtained. Other series of intermolecular comparative experiments also showed the selectivity of the hydrogenation for the sterically accessible alkene over other sites and even in the presence of inherently

• by water-soluble cavitands E and F. Site-selective hydrogenation of polyenols mediated by supramolecular encapsulated rhodium catalyst. Site-selective oxidation of steroids using cyclodextrin as the anchoring template. Site-selective oxidations of linear diterpenoids with the help of cage host A

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• greatly differ, as described by Allen and co-workers in their 2007 report on rhodium-catalyzed cyclodimerization reactions [59]. Moreover, desymmetrization of OBD produces more unique sites of reactivity allowing for the production of regioisomeric products. In 2019, Deng et al. described syn

• catalyzed by rhodium/diene to afford the 1,2,4-trisubstituted naphthalene framework 8 with complete regio- and stereocontrol (Scheme 1) [62][63]. In 2015, the Nishimura group reported the first iridium-catalyzed addition of salicylaldehydes 14 to bicyclic alkenes 11 (Scheme 1) [64]. Although a variety of

• independently studied the rhodium-catalyzed intermolecular hydroacylation reaction of salicylaldehydes with norbornadiene derivatives. It was found that electron-donating moieties at the C1-position were well tolerated in the hydroacylation reaction giving methyl- (15b), ethyl- (15c), and t-Bu- (15d) adducts in

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

• these indisputable advances, this approach has, thus far, predominantly relied on precious, often toxic, 4d and 5d transition metals, most prominently palladium, rhodium and iridium. In sharp contrast, the use of less expensive and less toxic Earth-abundant 3d transition metals continues to be

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

• products and processes that reduce or eliminate the use and generation of hazardous substances, as well as increase the atom economy of the reaction [9]. Among the transition-metal (TM) catalysts often used, the late transition metals like rhodium [10][11][12][13][14], palladium [15][16][17][18][19