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

• with sodium tetraarylboronates 64 was found to proceed with high diastereoselectivity under rhodium catalysis. Reddy and co-workers applied this methodology to the synthesis of 2-substituted pyrrolidines 66 [95]. The arylation of chlorinated imine (RS)-63 was performed with 2 mol % of an air-stable

• rhodium catalyst in dioxane, in the presence of 2 equivalents of MeOH, at 65 °C, leading to compounds 65 with high diastereomeric ratio. Crude amides 65 were converted into the corresponding pyrrolidines 66 in high yield by stirring at room temperature for 1 h in presence of 2.0 equivalents of LiHMDS

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• successful transition-metal catalysts are those based on rhodium, as evidenced by the number of reports that deal with the issue. The rhodium-catalysed addition of various boronic acids to conjugated cyclic enones (the so-called Hayashi–Miyaura reaction) is a well-established method for 3-unsubstituted

• substrates as well as for 2-unsubstituted chromones [17][18][19][21][22][23][24]. On the other hand, there is only one example of the usage of a rhodium-based catalyst for the addition of arylboronic acid to 3-substituted enones. The olefino-oxazoline ligand L18 has been used for the rhodium-catalysed

• is another challenging task. Nevertheless, it should be noted at this point that in the case of rhodium complex catalysis, the asymmetric addition of phenylboronic acid to enones in continuous flow has been successful [24]. In 2021, Walhers et al. presented a theoretical study based on the Q2MM

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• compounds as binucleophiles for the construction of various carbocycles, heterocycles as well as in asymmetric catalysis [44][45][46][47][48][49][50]. Our initial objective to trap the aza vinyl rhodium carbenoid using 1,3-dicarbonyl compounds to form pyrazolone was unsuccessful which instead led to the

• an easy pathway to synthesize such triazolylenones. Inspired by this result, we proceeded to optimize the reaction conditions to further improve the yield. Replacement of rhodium by copper (II) acetate slowed down the reaction with a marginal change in the yield of the product 3a (Table 1, entry 2

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• trans-12b can be also easily deprotected by a rhodium-catalyzed isomerization to the corresponding N-propenyl lactam followed by osmium tetroxide-catalyzed oxidative cleavage, providing lactam trans-17 in 62% yield. Additionally, the diastereomeric mixture of lactam 12o was subjected to oxidative N–O

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

• Prague, Czech Republic 10.3762/bjoc.17.44 Abstract The rhodium-catalyzed transannulation of N-perfluoroalkyl-1,2,3-triazoles with aromatic and aliphatic terminal alkynes under microwave heating conditions afforded N-perfluoroalkyl-3,4-disubstituted pyrroles (major products) and N-fluoroalkyl-2,4

• -disubstituted pyrroles (minor products). The observed selectivities in the case of the reactions with aliphatic alkynes were high. Keywords: pyrrole; transannulation; rhodium carbene; triazole; Introduction Pyrroles are known to be important structural moieties appearing in natural products, synthetic drugs

• -sulfonyl-1,2,3-triazoles (Scheme 1) [11][12][13][14][15][16][17]. We have recently reported that N-perfluoroalkyl-1,2,3-triazoles [18] undergo rhodium-catalyzed transannulation reactions leading to various nitrogen heterocycles, such as imidazoles, pyrrolones, imidazolones, oxazoles, azepines [19][20][21

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• penicillopepsin. Synthesis of phosphonodepsipeptides as prodrugs. Synthesis of phosphonodepsithioxopeptides 198. Synthesis of phosphonodepsipeptides. Synthesis of phosphonodepsipeptides with C-1-hydroxyalkylphosphonic acid. Synthesis of phosphonodepsipeptides with C-1-hydroxyalkylphosphonate via the rhodium

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• synthesis of inthomycin A ((+)-1). In the beginning, conversion of enyne 127 to the corresponding (Z,E)-dienylboronic ester 128 was investigated in the presence of rhodium(I)-catalyzed anti-selective hydroboration [72] under several conditions. Unfortunately, the yield of the desired (Z,E)-128 was found to

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

• as the phosphine-catalyzed [3 + 2] cycloaddition [17], platinum-catalyzed [3 + 2] cycloaddition [18], and Rhodium-catalyzed [3 + 2] cycloaddition [12], were invented and have been extensively used in natural product synthesis in the last decade. Many reviews focusing the method development of the all

• steps. A two-step synthesis from 108 produced 109, which was converted to (−)-ditryptophenaline (12) by using Overman’s protocol [48]. Rhodium-catalyzed [3 + 2] cycloaddition In 2014, Yang and co-workers reported an efficient rhodium-catalyzed intramolecular [3 + 2] cycloaddition of 110 to give [3.3.0

• ] and [3.4.0] bicyclic systems bearing two quaternary atoms at the bridgehead position [49]. For instance, enynol 110 was treated with 5 mol % of [RhCl(CO)2]2 and carbon monoxide to afford a [3.3.0] bicycle 111 in 87% yield (Scheme 8A). The proposed catalytic cycle of this elegant rhodium-catalyzed

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• reversibility was achieved by the addition of the rhodium porphyrin 19 that reversed the system reviving the state SelfSORT-I. Since both self-sorted states exhibited a distinct fluorescence due to the changes at the zinc porphyrin sites, luminescence was used for the selective detection of DABCO in a mixture

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• described the combination of rhodium and photoredox catalysis for the direct C–H ortho-olefination of arylamides (Figure 7) [74]. The procedure was performed under air at 80 °C and turned out to be efficient using a low loading of a Ru-based photosensitizer. A broad range of DGs could be installed on the

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• described, including the use of metals other than cobalt (such as rhodium, iridium, titanium, ruthenium, nickel, and palladium), or the use of CO surrogates such as aldehydes, alcohols and formates. Recently, its utility in flow chemistry has also been described [42]. Intramolecular Pauson–Khand reactions

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• functionalized thietanes, electron-deficient sulfur ylides were investigated in the ring expansion of thiiranes. However, the reactions failed due to the poor nucleophilicity of the electron-deficient sulfur ylides. However, in the presence of rhodium catalysts, the electron-deficient sulfur ylides were

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• HEH were used as H donors for both the benzyl and thiyl radicals, respectively. The HEH was needed to avoid the dimerization of the thiophenol to the disulfide (Scheme 11). Fu and co-workers have demonstrated the huge versatility of rhodium porphyrins for photocatalysis. In 2015, they showed that the

• hydration of terminal alkynes to ketones can be photocatalyzed by rhodium(III) tetrakis(p-sulfonylphenyl)porphyrin (RhIIITSPP) [37]. The coupling between RhIII(TSPP) and terminal alkynes produced the β-carbonylalkylrhodium porphyrin as a photoactive intermediate, whose irradiation produced the PhCOCH2

• highly regioselective photoinduced hydro-defluorination of perfluoroarenes with RhIII(TSPP) [38]. The oxidative addition of the perfluoroarene to the metal complex furnished the active rhodium aryl complex intermediate, which led to the product after visible light irradiation. The hydro-defluorination

Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas

• Zhenghui Liu,
• Peng Wang,
• Zhenzhong Yan,
• Suqing Chen,
• Dongkun Yu,
• Xinhui Zhao and
• Tiancheng Mu

Beilstein J. Org. Chem. 2020, 16, 645–656, doi:10.3762/bjoc.16.61

• pressure, cheap ligand and low metal dosage could significantly improve the practicability in both chemical researches and industrial applications. Keywords: cost-effective ligand; industrial catalysis; reductive carbonylation; rhodium catalyst; syngas; Introduction The exploration of environmentally

• chemical industry by offering a practical synthetic tool for the conversion of aryl iodides to arylaldehydes. Results and Discussion Effects of Rh species Rhodium salts coordinated with proper ligands have been reported to be able to realize the activation of CO and H2 and thus might achieve the reductive

• all with halogen anions), but also structural differences (e.g., crystal water, RhCl3 vs RhCl3·3H2O) of analogous Rh salts played an important role in the catalytic synthesis of benzaldehyde. Among all tested rhodium salts, RhCl3·3H2O afforded benzaldehyde in the highest yield and was chosen as the

Preparation and in situ use of unstable N-alkyl α-diazo-γ-butyrolactams in Rh^II-catalyzed X–H insertion reactions

• Maria Eremeyeva,
• Daniil Zhukovsky,
• Dmitry Dar’in and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2020, 16, 607–610, doi:10.3762/bjoc.16.55

• formation, in various RhII-catalyzed X–H insertion reactions, particularly the recently described rhodium carbene insertion into O–H [1], N–H [2] and S–H [3] bonds of alcohols, aromatic amines, and thiols, respectively. Herein, we report the results of these studies. Results and Discussion Three N-alkyl-α

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• dependence on external oxidants and harsh reaction conditions [83][84]. In this context, in 2014, Fabry et al. reported the use of novel dual photoredox catalytic systems made up of photoredox catalyst 11 and a rhodium catalyst to carry out the Weinreb amide C–H olefination shown in Scheme 1 [85]. By using

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

• Zachary Lee,
• Brandon R. Jones,
• Nyochembeng Nkengbeza,
• Michael Phillips,
• Kayla Valentine,
• Alexis Stewart,
• Brandon Sellers,
• Nicholas Shuber and
• Karelle S. Aiken

Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265

• extremely harmful to environmental and biological systems [3]. In light of mercury’s toxicity, the synthetic community has given much attention to the use of less harmful reagents. Success has been obtained with many other transition metal salts, for example, palladium(II) [4][5], rhodium(III) [6], copper

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• rhodium(III)-catalyzed intermolecular annulation has been established for the preparation of tetrazole-isoquinolone/pyridone hybrids. Several N-acylaminomethyltetrazoles were reacted with arylacetylenes to form the hybrid products in moderate to very good yields. The method relies on the capacity of the

• rhodium catalyst to promote C(sp2)–H activation in the presence of a suitable directing group. The Ugi-azide reaction provides broad molecular diversity and enables the introduction of the tetrazole moiety, which may further assist the catalytic reaction by coordinating the metal center. The scope of the

• activation of the N-benzamidomethyltetrazole core followed by isoquinolone-ring formation to furnish 4a. We endeavored two catalytic systems based on ruthenium and rhodium, which in our laboratory have proven success in this type of cyclization [32][48]. First, the alkynylation protocol was attempted using

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• their complexes with rhodium(I) [18], platinum(II) [30], and iridium(III) [31] were reported. In contrast, in our work, the 2-(imidazol-2-yl)pyridine unit is used as a heterocyclic moiety of diarylethenes with cyclopentenone, cyclopentene, and cyclohexenone ethene bridges. The novel ligands have been

Attempted synthesis of a meta-metalated calix[4]arene

• Christopher D. Jurisch and
• Gareth E. Arnott

Beilstein J. Org. Chem. 2019, 15, 1996–2002, doi:10.3762/bjoc.15.195

• ) and rhodium(III) complexes underwent spontaneous, chemoselective cyclometalation via C–H bond activation of the N-bound phenyl group (see Figure 2) [19]. Incorporation of a mesoionic carbene directing group onto the upper rim of a calix[4]arene therefore offered potential for a new route to calix[4

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• -ring system; palladium-catalyzed carbonylation and in situ lactone formation, and rhodium(II)-catalyzed double bond migration to construct the D-ring; and palladium-catalyzed Csp2–H oxygenation to install the C-14 hydroxy group. In 2016, Qin and co-workers developed a catalytic asymmetric route toward

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

• associated with the reported methodologies. Amongst various reported TMs, the participation of copper as the catalyst has been used in the largest number of cases followed by the use of palladium, rhodium, and others. It has been further observed that lanthanum, scandium, and vanadium have been very seldomly

• easy recovery and reusability [69]. The role of rhodium in synthetic chemistry Rhodium in the form of Wilkinsons catalyst [RhCl(PPh3)3] played a major role in the field of catalysis [70]. Rhodium is capable of catalyzing a number of organic reactions viz., heterocyclic alkylation and arylation with a

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• isocyanides and sulfur [76] can be enhanced using various catalysts such as selenium, molybdenum, copper, rhodium [77][78][79][80][81][82] or tellurium [83] providing the isothiocyanates in excellent yields. These approaches on the other hand suffer from the use of heavy metals, toxic chalcogens and/or long

Selective detection of DABCO using a supramolecular interconversion as fluorescence reporter

• Indrajit Paul,
• Debabrata Samanta,
• Sudhakar Gaikwad and
• Michael Schmittel

Beilstein J. Org. Chem. 2019, 15, 1371–1378, doi:10.3762/bjoc.15.137

• Information File 1, Figure S21) to satisfy maximum site occupancy. Upon the addition of 2 equiv of rhodium porphyrin 3 [37], DABCO was selectively removed from complex 12 [38] affording the sandwich complex 7 = [(3)2(4)] leaving complex 11 untouched and liberating two equiv of 10 (incomplete self-sorting

• , Scheme 2). This phenomenon is readily explained considering the stronger binding of rhodium porphyrin 3 to DABCO (Δlog β = 2.40) compared with zinc porphyrin (Supporting Information File 1, Figure S22). With this ligand shuffling in mind, we wanted to probe the guest-induced double self-sorting depicted

• , DABCO is a highly selective trigger for the structural rearrangement of rectangle 5 to sandwich complex 6. Finally, we tested the reversibility of the system by addition and removal of DABCO using rhodium porphyrin 3 as scavenger of DABCO. In line with the results of the model self-sorting scenarios in