Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• new C-centered radical. The first possible pathway relied on a rebound cycle where this radical recombined with the [Cu(II)] complex to generate a [Cu(III)] species. Then, a reductive elimination closes the catalytic cycle, delivering the product and regenerating the catalyst, along with an exchange

• can deliver the product through a reductive elimination, along with the [Cu(I)] species in the ground state. 1.2 Reduction reactions In 2013, Fensterbank, Goddard, and Ollivier reported the use of the homoleptic complex [Cu(I)(dpp)2]PF6 for the reduction of symmetrical diaryliodonium salts (Scheme 8

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• in the reaction, resulting from an oxidative addition of the trifluoromethylselenolated copper(I) complex to the α-brominated unsaturated carbonyl compound. Afterwards, a reductive elimination would take place to afford the α-trifluoromethylselenylated α,β-unsaturated carbonyl compound and copper(I

• reacted with the copper(II) complex, forming a new copper(III) intermediate. After reductive elimination, the desired difunctionalized compounds were formed. Tetramethylammonium trifluoromethylselenolate salt (Me4NSeCF3) Tetramethylammonium trifluoromethylselenolate was reported by the group of Tyrra in

Allylic cross-coupling using aromatic aldehydes as α-alkoxyalkyl anions

• Akihiro Yuasa,
• Kazunori Nagao and
• Hirohisa Ohmiya

Beilstein J. Org. Chem. 2020, 16, 185–189, doi:10.3762/bjoc.16.21

• allylpalladium(II) species F that is generated through the oxidative addition of an allylic carbonate 2 across a palladium(0)–DPPF complex E, followed by reductive elimination from G produces the homoallylic alcohol 3 and then regenerate A and E for the next catalytic cycle [20][21][22][23]. Conclusion In

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• and the new bond formation through reductive elimination should be less hindered, but remarkably, no reaction was observed either with the methyl ester 26b or the free acid 27b (Table 2, entries 6 and 7). Next we explored if amino-substituted silicon rhodamine 28c is accessible via Pd-catalysis. The

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

• using a secondary amide as directing group (Scheme 1C) [32][48]. In these protocols, the amide group plays a dual behavior of directing group and reaction center, as it participates in the final ring-closing reductive elimination. Herein, we report the synthesis of a new class of tetrazolo-isoquinolone

• subsequent migratory insertion furnishes the seven-membered metallacycle D. Finally, reductive elimination leads to compounds 4a and the concomitant reoxidation of Rh(I) to Rh(III) by the Cu(II) salt completes the catalytic cycle. Conclusion In conclusion, we have developed a versatile method for the

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• intermediate B through the C–H bond-activation process. Oxidative addition of the intermediate B with Selectfluor affords the palladium(IV) species C, followed by reductive elimination and ligand dissociation to give the final product. Similar to these publications in strategy and products, in the same year

• transformation employed Pd2(dba)3/t-BuBrettPhos and CsF to convert aryl alcohols to aryl fluorides at 180 °C under microwave conditions (Scheme 14). The proposed catalytic cycle of this aryl fluorination is also shown. Only reductive elimination was investigated by Larhed, because this reaction step is crucial

• NFSI to give the highly reactive species F–Pd(IV)1a)2-N(SO2Ph)2 (C), which produces the product 2a and reductive elimination intermediate 1a-Pd(II)-N(SO2Ph)2 (D). Finally, intermediate A regenerates from intermediate D by aid of the catalytic amount of HNO3 released during the C–H activation step. In

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

• literature report [32]). This was presumably due to ruthenium undergoing a reductive elimination and the chloride remaining on the triazolium moiety. Crystallization also proved to be futile after many attempts under many different conditions. The only crystals that formed were either found to be the

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

• 2-AP to Cu(OTf)2, forming an intermediate 7, that was followed by migratory insertion by haloalkyne (Scheme 4). The organocopper species 8 thus formed would undergo deprotonation/oxidation and finally reductive elimination to give the cyclized product 6 (Scheme 4). Along with the unprecedented

• generation of iminyl radical intermediate 31 by homolytic cleavage of the C–N bond which was followed by reductive elimination and oxidation to yield final compound 21. Inspired by the work of Wang et al. [15] who have exploited a Cu(II)-catalyst for the construction of pyrido[1,2-a]benzimidazoles Li and Xie

• abstraction from the sp3 carbon atom leading to the formation of six-membered Cu(III) species 42. Furthermore, consecutive isomerization/oxidation/reductive elimination leads to the generation of final compound 37 with regeneration of the Cu(I) catalyst (Scheme 14). The presence of EDGs as compared to EWGs on

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• furnishes an acylpalladium complex 65, which, after elimination of hydrogen bromide and subsequent reductive elimination of palladium from intermediate 66, affords 57 with regeneration of Pd(0). 2-Vinylbenzoic acids 67 are also appropriate substrates for the preparation of isoindolinones 71 through a four

Intramolecular cascade annulation triggered by rhodium(III)-catalyzed sequential C(sp²)–H activation and C(sp³)–H amination

• Liangliang Song,
• Guilong Tian,
• Johan Van der Eycken and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 571–576, doi:10.3762/bjoc.15.52

• intramolecular migratory insertion affords intermediate C. Reductive elimination and subsequent oxidative addition give intermediate D. Then two pathways are involved in the following steps. In the main pathway (path a), intermediate D undergoes β-H elimination and tandem cyclization to give product 3a and Rh–H

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• undergoes fast decomposition as a result of β-transfer of the silyl group in the appropriate β-(silyl)rutenacyclobutane complex to ruthenium followed by reductive elimination of the corresponding propene derivative (Scheme 1c). The transformation resulted in complexes that do not contain a carbene ligand

A novel and efficient synthesis of phenanthrene derivatives via palladium/norbornadiene-catalyzed domino one-pot reaction

• Yue Zhong,
• Wen-Yu Wu,
• Shao-Peng Yu,
• Tian-Yuan Fan,
• Hai-Tao Yu,
• Nian-Guang Li,
• Zhi-Hao Shi,
• Yu-Ping Tang and
• Jin-Ao Duan

Beilstein J. Org. Chem. 2019, 15, 291–298, doi:10.3762/bjoc.15.26

• compound C with a five-membered palladacycle. C undergoes the process of oxidative addition with ortho-bromobenzoyl chloride to give the PdIV intermediate D, and E can be obtained via a reductive elimination reaction. A novel aryl-PdII species F is formed through removing carbon monoxide from E. Ultimately

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

• 106. The Togni reagent (105) reacts with CuCl to generate Cu(III) complex 108. Then, the intermediated 109 is generated from the electrophilic attack of copper(III) 108 with cyclopropanol 91. Finally, the desired product 106 is formed through reductive elimination of CuCl in intermediated 109. On the

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• a). Subsequently, the reductive elimination of methane from B yields the low-valent allyl-Co(I) species C (step b). Then, C–C bond formation at the γ-position occurs via a reaction with CO2, affording the carboxylate Co species D (step c). Finally, a linear carboxylated product is obtained by the

• bond, affording Rh(III) species B (step a). Subsequently, the reductive elimination of methane from B affords the low-valent Rh(I) species C. Then, C–C bond formation with CO2 proceeds, and Rh carboxylate D is formed. Finally, the carboxylated product is obtained by the transmetalation between D and

• this transformation, the reaction pathways depicted in Scheme 41 can be envisaged. The Rh(I) species A reacts with a diyne to afford rhodacycle B (step a). Then, the reaction of B with CO2 produces the seven-membered rhodium intermediate C (step b), from which reductive elimination occurs to yield its

Synthesis of indolo[1,2-c]quinazolines from 2-alkynylaniline derivatives through Pd-catalyzed indole formation/cyclization with N,N-dimethylformamide dimethyl acetal

• Antonio Arcadi,
• Sandro Cacchi,
• Giancarlo Fabrizi,
• Francesca Ghirga,
• Antonella Goggiamani,
• Antonia Iazzetti and
• Fabio Marinelli

Beilstein J. Org. Chem. 2018, 14, 2411–2417, doi:10.3762/bjoc.14.218

• )acetylene (1) with aryl or vinyl halides and triflates followed by cyclization reactions (Scheme 1) [19]. The reaction, which tolerates a variety of important functional groups, likely involves the formation of the indole intermediates 2 (through aminopalladation/reductive elimination) [20][21] followed by

• )anilines 15 (see below). Results and Discussion We have previously reported that arylboronic acids 12 can be used in place of aryl halides in the Pd-catalyzed synthesis of indoles through aminopalladation/reductive elimination reaction from 2-alkynyltrifluoroacetanilides [24]. This reaction is carried out

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

• Ken Tamamoto,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2018, 14, 2375–2383, doi:10.3762/bjoc.14.213

• to the corresponding Cu(I) species, (ii) oxidative addition of a CAr–I bond to the Cu(I) atomic center to generate Cu(III) species, and (iii) reductive elimination of the product 4a along with the regeneration of the Cu(I) salt. When the initial transmetallation from 2-Zn to the reactive Cu(I

• facilitates the subsequent reductive elimination to form the desired coupling product. This acceleration effect of the ester functional group at the ortho-position led to a reduction in the chemical substances used. That is to say, the product 4j was obtained in a quantitative manner even when the reaction of

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• or a C–H activation with high-valent cobalt to give A2 via deprotonation, followed by migratory insertion and reductive elimination or protonation (Scheme 3). We believe that this review will be helpful to the researchers for their future research on hydroarylation using earth-abundant metal

• found intermolecular kinetic isotope effect (KIE) of kH/kD = 2.1 and H/D crossover studies strongly suggest that the reaction proceeds through an oxidative addition of a C–H bond to low-valent cobalt followed by alkyne insertion and reductive elimination. Furthermore, the new C–C bond formation occurred

• -products. Then, coordination of the alkyne with the cobalt catalyst afforded B1 and the oxidative addition of C–H gave the cobalt complex B2. Intramolecular insertion of the Co–H bond into the alkyne and subsequent reductive elimination of the less-hindered alkenyl carbon with aryl group in B3 provides the

Cobalt-catalyzed nucleophilic addition of the allylic C(sp³)–H bond of simple alkenes to ketones

• Tsuyoshi Mita,
• Masashi Uchiyama,
• Kenichi Michigami and
• Yoshihiro Sato

Beilstein J. Org. Chem. 2018, 14, 2012–2017, doi:10.3762/bjoc.14.176

• to the case of nucleophilic η1-allylpalladium species [31][32][33][34][35][36][37][38][39]), whereas the cobalt atom preferred to reside at the internal position when allylarenes and 1,4-dienes were employed in our previous studies [28][29]. Subsequently, reductive elimination of methane from III

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• intermediate 75. Subsequently, this intermediate is attacked by the palladium catalyst under a CO atmosphere to form the alkyl palladium species 76. Finally, the reductive elimination at the iodine(III) center and CO insertion into the newly formed C–Pd bond, affords the oxycarbonylation products 74 (Scheme 21

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• (Scheme 4b). The intermediate Cu–Bpin, then, could undergo an oxidative addition into the CF3–I bond to give 8 that, after a CF3 radical transfer, would afford the radicals 9 and 10. Radical recombination followed by reductive elimination would finally lead to the E-product and regenerate the Cu–Bpin

• to the triple bond of 22 to give the intermediate 26, followed by the reductive elimination of the trivalent iodine motif to afford the palladium-vinylidene 27. This would undergo a nucleophilic addition of the imine and a subsequent proto-demetallation to give enamine 29. A series of rearrangements

• and migratory addition into the proximal alkyne. Transmetalation of the vinylpalladium with the boronic acid and reductive elimination finally leads to alkylidenefluorenes 49. This multicomponent strategy allows the variation of the alkyne, the boronic acid and the diaryliodonium salts, but the use of

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• potassium salt D upon treatment with KOt-Bu. Reductive elimination from C produces the product 7, under regeneration of the Cu(I) species. The released aryl iodide 2 on the other hand then undergoes oxidative addition forming the Cu(III) species E, which can provide intermediate F upon reaction with the

• potassium salt D and the release of potassium iodide. Reductive elimination then affords the second S-aryl dithiocarbamate 7’. If both aryl groups are not transferred to the same reaction centre in metal-mediated diarylations when unsymmetrical diaryliodonium salts are used as aryl-transfer reagents, poor

• deprotonation of the imidazolyl group to give betain A, which binds to a Cu(I)-OTf fragment leading to complex B. Next, the aryl group is transferred from the iodine to the copper atom leading to the Cu(III) complex D via a five-membered transition state C. Reductive elimination through transition state E

Iodine(III)-mediated halogenations of acyclic monoterpenoids

• Laure Peilleron,
• Tatyana D. Grayfer,
• Joëlle Dubois,
• Robert H. Dodd and
• Kevin Cariou

Beilstein J. Org. Chem. 2018, 14, 1103–1111, doi:10.3762/bjoc.14.96

• (Scheme 7a) [12]. We ruled out a possible direct reaction between the olefin and the hypervalent iodine(III) reagent as in the absence of any halide no reaction occurred within 1 h (Scheme 7b). A reductive elimination would then generate hypohalite R’OX which is presumably the active electrophilic species

• . If the reductive elimination only occurred after a second ligand exchange it would then give X2 which is generally a less efficient electrophilic species than the corresponding acetoxyhypohalite, especially trifluoroacetoxyhypohalites [26]. Indeed, when we reacted geranyl acetate 1a with bromine we

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• radical to give a diorganocobalt intermediate C. The C–C-bond rotation of the radical anion 2•− or the transiently formed alkenyl radical might be responsible for the stereochemical mutation of the C=C bond observed in some cases. The reductive elimination of C and subsequent transmetalation with the

Palladium-catalyzed ortho-halogenations of acetanilides with N-halosuccinimides via direct sp² C–H bond activation in ball mills

• Zi Liu,
• Hui Xu and
• Guan-Wu Wang

Beilstein J. Org. Chem. 2018, 14, 430–435, doi:10.3762/bjoc.14.31

• inserts into the ortho C–H bond of the anilides after coordination to the oxygen atom of the amide moiety, affording the species A. Oxidative addition of the species A with NIS generates the Pd(IV) complex B. Finally, the iodinated product is provided by reductive elimination along with regeneration of Pd

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• trifluoroacetate (Scheme 6), followed by oxidative addition with aryl iodides and the trifluoromethylated products were delivered through reductive elimination. Later, Buchwald and co-worker [19] firstly developed an efficient, scalable technique to introduce a trifluoromethyl group into aryl iodides with CF3CO2K

• . Finally, reductive elimination of the intermediate D would afford the desired product and regenerate Cu(I) catalyst to restart the catalytic cycle. Direct trifluoromethylation of C(sp2)–H with a radical trifluoromethylation reagent (CF3SO2Na): The radical trifluoromethylation via direct C(sp2)–H

• species B is formed through the coordination/deprotonation of the alkyne in the presence of base, followed by oxidative addition of CF3+ and reductive elimination providing the desired product. The copper complex A was regenerated to complete the catalytic cycle. In the same year, the group of Fu and Guo