Palladium-catalyzed regio- and stereoselective synthesis of aryl and 3-indolyl-substituted 4-methylene-3,4-dihydroisoquinolin-1(2H)-ones

• Valeria Nori,
• Antonio Arcadi,
• Armando Carlone,
• Fabio Marinelli and
• Marco Chiarini

Beilstein J. Org. Chem. 2020, 16, 1084–1091, doi:10.3762/bjoc.16.95

• aminopalladation/reductive elimination. Keywords: alkynylanilines; arylboronic acids; indoles; isoquinolinones; palladium; Introduction The isoquinolinone nucleus is a key constituent of many natural products [1][2][3] and pharmaceuticals [4][5][6]. Substituted isoquinolinones have been found in biologically

• chemical and physical properties of the products. Furthermore, over the years, we have reported a general methodology for the Pd-catalyzed synthesis of 3-substituted indoles, now referred to as the “Cacchi reaction” [34], through an aminopalladation/reductive elimination sequence starting from 2

• halides [38], α-iodoenones [39], or by transmetalation of a Pd(II) species with boronic acids [33]. In this context, we decided to explore the use of substrates 2 in the reaction with 2-alkynyltrifluoroacetanilides 5 through a sequential cyclocarbopalladation/aminopalladation/reductive elimination process

Synthesis and anticancer activity of bis(2-arylimidazo[1,2-a]pyridin-3-yl) selenides and diselenides: the copper-catalyzed tandem C–H selenation of 2-arylimidazo[1,2-a]pyridine with selenium

• Mio Matsumura,
• Tsutomu Takahashi,
• Hikari Yamauchi,
• Shunsuke Sakuma,
• Yukako Hayashi,
• Tadashi Hyodo,
• Tohru Obata,
• Kentaro Yamaguchi,
• Yasuyuki Fujiwara and
• Shuji Yasuike

Beilstein J. Org. Chem. 2020, 16, 1075–1083, doi:10.3762/bjoc.16.94

• the diselenide 2. On the other hand, in the presence of excess imidazopyridine, the oxidative addition of imidazopyridine 1 to B, followed by the aromatization of C leads to the intermediate D. The intermediate D undergoes a reductive elimination to give the selenide 3, with the generation of Cu(I

• -position to form the intermediate C and the selenide anion F. The intermediate C undergoes a reductive elimination and aromatization to give the selenide 3 and Cu(I). Moreover, the Cu-mediated electrophilic addition of 3 and selenium affords G, which aromatizes to form E and then probably undergoes a

• reductive elimination to afford the diselenide 2. The anticancer activity of the novel synthesized bis(2-arylimidazo[1,2-a]pyridin-3-yl) diselenides 2 and selenides 3 was evaluated in human cervical cancer HeLa cells (Figure 5). At 25 µM, each compound significantly decreased the cell viability compared to

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• presence of the nickel catalyst and a base via a typical oxidative addition, insertion, and reductive elimination sequence to afford the desired product (Scheme 29). In the absence of K2HPO4, only traces of the desired product were detected. Other known photosensitizers, such as acetone (4), acetophenone

• formed reacts with an acyl radical 175 to give the nickel(III) complex 178, which could then undergo a reductive elimination reaction to furnish the desired ground state benzophenone product 172. The nickel(0) catalyst can then be regenerated by SET (Scheme 41). However, they suggested that the first

Synthesis of C₇₀-fragment buckybowls bearing alkoxy substituents

• Yumi Yakiyama,
• Shota Hishikawa and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2020, 16, 681–690, doi:10.3762/bjoc.16.66

• is formed. Two competitive processes, the reductive elimination from B to give the product 5b, and the 1,5-palladium migration from A to C through B, might exist, and from C, after the bond rotation, the intermediate D would form to afford the isomer 5c. The selectivity of these two processes are

Copper-catalyzed O-alkenylation of phosphonates

• Nuria Vázquez-Galiñanes,
• Mariña Andón-Rodríguez,
• Patricia Gómez-Roibás and
• Martín Fañanás-Mastral

Beilstein J. Org. Chem. 2020, 16, 611–615, doi:10.3762/bjoc.16.56

• groups, and final reductive elimination would form the new C(sp2)–O bond, providing an acyclic enol phosphonate with concomitant regeneration of the Cu(I) catalyst (Scheme 1b). Herein we report the successful realization of such a copper-catalyzed oxygen-alkenylation strategy and show that a range of

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