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

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• thiyl radical addition forms a [NiII] intermediate. A second single-electron reduction by [IrII] yields the respective [NiI] sulfide. After oxidative addition of the aryl iodide to the [NiI] sulfide complex, the respective C–S cross-coupling product is formed via reductive elimination from the [NiIII

• , yielding a [NiII] species. Single-electron reduction by 4CzIPN•− generates a [NiI] sulfide complex and closes the photocatalytic cycle. Oxidative addition of the bromoalkyne and subsequent reductive elimination forms the corresponding alkynyl sulfide and closes the [Ni]-catalyzed cycle. The reaction

Reactivity of bromoselenophenes in palladium-catalyzed direct arylations

• Aymen Skhiri,
• Ridha Ben Salem,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2017, 13, 2862–2868, doi:10.3762/bjoc.13.278

• Scheme 5 can be proposed. The first step is probably the oxidative addition of the 2-bromoselenophene to Pd(0) to afford the Pd(II) intermediate A. Then, after elimination of KBr with KOAc, a concerted metalation–deprotonation pathway involving an heteroarene gives B. Reductive elimination affords the 2

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• obtained after reductive elimination of species 18. The other envisaged pathway was the oxidation of intermediate 17 through a SET to form the cationic species 19, which would then afford the final product after a C–N bond formation. Liu and co-workers also proposed a racemic version of this reaction

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• A, transmetallation of the boronic acid with the active Cu(II) species 73 gave the arylcopper(II) complex 74, which reacted with CF3• to afford the arylcopper(III) complex 75. Next, a reductive elimination gave the trifluoromethylated product with release of the Cu(I) complex 76 that was re-oxidised

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• –89% and a high stereoselectivity (Scheme 6) [14][15]. The proposed mechanism of this reaction is as described in Scheme 7 [14][15]. Oxidative addition of the vinyl triflate to the catalyst results in complex 6 that upon reductive elimination (an added phosphine) provides the vinylphosphonium salt and

Ni nanoparticles on RGO as reusable heterogeneous catalyst: effect of Ni particle size and intermediate composite structures in C–S cross-coupling reaction

• Debasish Sengupta,
• Koushik Bhowmik,
• Goutam De and
• Basudeb Basu

Beilstein J. Org. Chem. 2017, 13, 1796–1806, doi:10.3762/bjoc.13.174

• reductive elimination. A more detailed study describing Pd- or Cu-catalyzed C–S coupling reactions as compared to Ni-catalyzed reaction has been published [7][53][54]. However, as proposed in previous investigations on the Ni-catalyzed C–S coupling reaction [15][22][23], the catalytic cycle here is likely

• , and then the reductive elimination could result in the formation of Ar–SPh (Figure 6). The resulting Ni(II) species could be converted mostly to Ni(OH)2 NPs in the presence of water during washing and subsequent recovery, as examined from the powder XRD and HRXPS of the recovered catalyst after the

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• with alkyne M. This is facilitated by coordination of L with RuII, followed by C–H activation to afford N. Migratory insertion of M on N generate O and subsequent reductive elimination of O afforded the desired compounds (Scheme 26). In another example Yuan et al. [88] demonstrated that a catalytic

• generate U which undergoes further reductive elimination to afford 90 (Scheme 33). A ferric chloride (FeCl3)-catalyzed tert-butyl hydroperoxide (TBHP)-mediated synthesis of 2-arylquinazolin-4(1H)-one 92 was reported by Zhao et al. o-Aminobenzamides are reacted with diverse alcohols with 2 mol % of ferric

Unpredictable cycloisomerization of 1,11-dien-6-ynes by a common cobalt catalyst

• Abdusalom A. Suleymanov,
• Dmitry V. Vasilyev,
• Valentin V. Novikov,
• Yulia V. Nelyubina and
• Dmitry S. Perekalin

Beilstein J. Org. Chem. 2017, 13, 639–643, doi:10.3762/bjoc.13.62

• -membered metallacycle 7, which can undergo reductive elimination to give the cyclohexene 2, or β-hydride elimination followed by the reductive elimination to give the diene 3. It may be speculated that the steric crowding in the intermediate 7 determines the direction of the reaction. In contrast to the

• relatively small dppe ligand, two large Ph3P ligands hinder the β-elimination (which requires proximal syn-position of metal and hydrogen) and therefore push reaction towards direct reductive elimination to give 2. Alternatively, β-hydride elimination can proceed in the intermediate 6 to give the hydride

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• formation of a copper(I) complex from the 1,2-ketone and the hydroxy group, which further coupled with aryl iodides through oxidative addition to generate a copper(III) complex. Phenols were liberated by the following reductive elimination [29]. You and co-workers used the same copper catalyst and reported

Direct arylation catalysis with chloro[8-(dimesitylboryl)quinoline-κN]copper(I)

• Sem Raj Tamang and
• James D. Hoefelmeyer

Beilstein J. Org. Chem. 2016, 12, 2757–2762, doi:10.3762/bjoc.12.272

• ]. Recently, we reported the Pd(II) complex catalyzed Heck-type C–C coupling [51]. The observation may implicate reductive elimination and oxidative addition can cycle repeatedly on the palladium center coordinated to 1. With this in mind, we sought to utilize the Cu(I) complex, chloro[8-(dimesitylboryl

• reactions and, more specifically, direct arylation have been the subject of intense interest. Mechanistic models appear to diverge along those favoring oxidative addition/reductive elimination via Cu(I)/Cu(III) versus proposals favoring a single electron transfer (SET) pathway [55][56]. In the base-promoted

• -enediol in situ as an electron donor [62]. While the SET mechanism has drawn much interest, our observation of large rate enhancement upon addition of the preformed catalyst 2 may be better described with a metalation–deprotonation step followed by oxidative addition/reductive elimination (Scheme 2) [63

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• a cyclic enamine followed by reductive elimination of the amine moiety using lithium in liquid ammonia [150]. We may be able to repeat the exercise now using all possible 3-partition target bond dissection maps shown in Figure 6. For brevity the results are given in Supporting Information File 1 in

Enantioconvergent catalysis

• Justin T. Mohr,
• Jared T. Moore and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2016, 12, 2038–2045, doi:10.3762/bjoc.12.192

• these two complexes was not observed directly for this system, extrapolation from related systems gives a rate more than 105 times greater than the observable rates of C–P reductive elimination. Since the rate of inversion is much greater than the rate of bond formation, Curtin–Hammett/Winstein–Holness

Catalytic Chan–Lam coupling using a ‘tube-in-tube’ reactor to deliver molecular oxygen as an oxidant

• Carl J. Mallia,
• Paul M. Burton,
• Alexander M. R. Smith,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1598–1607, doi:10.3762/bjoc.12.156

• more atom economical way of catalysing the Chan–Lam reaction using a sub-stoichiometric amount of copper and oxygen gas as the oxidant. The use of oxygen provides the necessary oxidant to reoxidise the Cu(I) that forms after the C–N reductive elimination back to Cu(II), allowing for sub-stoichiometric

A T-shape diphosphinoborane palladium(0) complex

• Patrick Steinhoff and
• Michael E. Tauchert

Beilstein J. Org. Chem. 2016, 12, 1573–1576, doi:10.3762/bjoc.12.152

• between the oxidations states Pd(0)/Pd(II) is of potential interest for organometallic transformations involved in homogeneous catalysis, such as the reductive elimination. Here we report the synthesis of the diphosphinoborane (o-PCy2-C6H4)2BPh ligand CyDPBPh. CyDPBPh reacts with CpPd(η3-C3H5) yielding