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

Methylpalladium complexes with pyrimidine-functionalized N-heterocyclic carbene ligands

• Dirk Meyer and
• Thomas Strassner

Beilstein J. Org. Chem. 2016, 12, 1557–1565, doi:10.3762/bjoc.12.150

• like the bis(1,1'-dimethyl-3,3'-methylenediimidazoline-2,2'-diylidene)palladium(II) dibromide [L2PdBr2] consists of three steps: electrophilic substitution, oxidation and reductive elimination involving a palladium(IV) intermediate [26]. But we also experimentally set out to investigate potential

• (see experimental details). The result indicates that an oxidation/reductive elimination cycle took place (Scheme 3, upper pathway). The direct reductive elimination of methyl trifluoroacetate from complex 13 by heating complex 13 in DMSO-d6 up to 90 °C in the presence of sodium trifluoroacetate [30

• bistrifluoroacetate complex 14 from this complex under oxidizing reaction conditions points to a Pd(II)/Pd(IV)-mechanism for the reductive elimination of the observed product methyl trifluoroacetate. The dimethyl complex [((pym)^(NHC-DIPP))PdII(CH3)2] 15 could be synthesized to demonstrate the accessibility of these

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• dissociation, followed by an oxidative addition/pseudorotation/reductive elimination pathway with short-lived, elusive seven-coordinate hydrido tungsten(II) intermediates cis(N,H)-W(CO)4(H)(Z-15) and cis(C,H)-W(CO)4(H)(Z-15). Keywords: carbene complexes; ferrocene; imine; mechanism; tungsten; Introduction

• (pathway 3a and 3b, Scheme 4) giving W(CO)4(E-3) or W(CO)4(Z-3), respectively. Furthermore, the free coordination site in W(CO)4(E-2) or W(CO)4(Z-2) offers an oxidative addition/pseudorotation/reductive elimination pathway via the hydrido tungsten(II) complexes W(CO)4(H)(Z-15) with the formally anionic

• (H)(Z-15) (ΔG‡ = 86 kJ mol−1) enables a low-energy reductive elimination (ΔG‡ = 40 kJ mol−1) to give the imine complex W(CO)4(Z-3) (Figure 1). The overall Gibbs free energy of activation amounts to only ΔG‡total = 183 kJ mol−1 with the RDI W(CO)4(E-2) and the RDTS TS(W(CO)4(Z-2) → cis(N,H)-W(CO)4(H

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• phosphorylated quinazoline 203 through reductive elimination. A silver-catalyzed three-component reaction of α-isocyanophosphonates 206, ketones 205 and amines 204 under microwave irradiation to afford (2-imidazolin-4-yl)phosphonates 210 has recently been reported (Scheme 43) [81]. The yields of the products

Palladium-catalyzed picolinamide-directed iodination of remote ortho-C−H bonds of arenes: Synthesis of tetrahydroquinolines

• William A. Nack,
• Xinmou Wang,
• Bo Wang,
• Gang He and
• Gong Chen

Beilstein J. Org. Chem. 2016, 12, 1243–1249, doi:10.3762/bjoc.12.119

• , entries 9 and 10) [34][35]. By analogy with similar Pd-catalyzed directed C–H halogenation reactions, we speculate that the catalytic cycle follows a sequence of C−H palladation, oxidative addition and reductive elimination [36][37]. With the best conditions in hand (Table 1, entries 9 and 10), we then

Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• the product from their 5-membered isoxazoline-containing palladacycle [160][168][225]. Although BQ is sometimes used as a ligand for palladium to accelerate reductive elimination [103][226][227][228][229][230], its presence was not necessary in our stoichiometric reaction of a cationic 6-membered ring

• hydroquinone as a byproduct. For the Fujiwara–Moritani coupling, addition of the palladacycle 6 to an acrylate followed by β-hydride elimination and reductive elimination of HPd+BF4− would result in a Pd(0) species unable to participate in palladacycle formation until it is oxidized by BQ to Pd2+(BF4)2

• presumably starts from the generation of a cationic palladacycle, which may undergo a facile transmetalation with an arylboronic acid without prior activation by base (Scheme 24) [241][242][243][244][245][246][247][248]. This step is followed by reductive elimination of a diarylpalladium(II) species

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• alkoxide species C. Reductive elimination of species C gave the product and regenerated the active iridium catalyst. Recently, Qiu and co-workers developed a novel chiral ligand L5 based on a chiral-bridged biphenyl backbone and successfully achieved the asymmetric addition of arylboronic acids to N

• protonolysis of I by adamantanecarboxylic acid, followed by exchange of the carboxylate II with 3-hydroxy-2-oxindole (rapid). β-Hydride elimination of III generated ruthenium hydride IV and N-benzylisatin. Subsequent C–H reductive elimination of IV produced the product and regenerated the ruthenium(0) complex

Pyridylidene ligand facilitates gold-catalyzed oxidative C–H arylation of heterocycles

• Kazuhiro Hata,
• Hideto Ito,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2015, 11, 2737–2746, doi:10.3762/bjoc.11.295

• be a key step in the catalytic cycle consisting of transmetalation with arylsilane, C–H activation and reductive elimination [69]. While gold(I) complexes bearing various ligands are used as gold(III) precursors, it remains unclear whether ligands can still coordinate to the gold center or not under

• electrophilic metalation of heteroarene 1 with C with concurrent generation of an acid (HX) produces diarylated gold(III) species D. Finally, the reductive elimination from D releases the coupling product 3 along with the regeneration of gold(I) species A. The side reaction leading to the homocoupling product

• calculations on the oxidation process of the AuCl(ligand) to AuCl3(ligand) also clarified the advantage of the PyC ligand over IPr by 3.6 kcal mol–1 (see Supporting Information File 1 for details). While it still remains unclear how the PyC ligand affects the transmetalation, C–H metalation and reductive

Copper-catalyzed aminooxygenation of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives

• Yan Li,
• Xue Zhou,
• Guangfan Zheng and
• Qian Zhang

Beilstein J. Org. Chem. 2015, 11, 2721–2726, doi:10.3762/bjoc.11.293

• (II)–F species IV. The combination of the intermediates III and IV gave the Cu(III) species V having a C–Cu bond, which reacted with 2a to generate Cu(III)–O species VI, along with the loss of HF. Finally, the reductive elimination of VI afforded aminooxygenation product 3g. Finally, we tried to

Recent advances in copper-catalyzed C–H bond amidation

• Jie-Ping Wan and
• Yanfeng Jing

Beilstein J. Org. Chem. 2015, 11, 2209–2222, doi:10.3762/bjoc.11.240

• applicable for the synthesis of 2-amino-1-methylindoles 37 via C–H amidation of indoles 36 by employing benzene as the medium (Scheme 11). While the authors proposed that the mechanism in the selective C-2 amidation of N-methylindoles resulted from a classical oxidative addition/reductive elimination Cu(III

Coupling of α,α-difluoro-substituted organozinc reagents with 1-bromoalkynes

• Artem A. Zemtsov,
• Alexander D. Volodin,
• Vitalij V. Levin,
• Marina I. Struchkova and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2015, 11, 2145–2149, doi:10.3762/bjoc.11.231

• interacts with bromoalkyne 3 either by oxidative addition generating copper(III) intermediate 6 or by triple bond carbometallation [38] generating copper(I) intermediate 7. Subsequent reductive elimination (from 6) or β-elimination (from 7) leads to the product and regenerates the copper(I) catalyst

The facile construction of the phthalazin-1(2H)-one scaffold via copper-mediated C–H(sp²)/C–H(sp) coupling under mild conditions

• Wei Zhu,
• Bao Wang,
• Shengbin Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2015, 11, 1624–1631, doi:10.3762/bjoc.11.177

• organocopper(II) complex M2, which undergoes Cu(OAc)2-promoted oxidation and intramolecular C–H cupration to deliver chelated organocopper(III) intermediate M4. The corresponding product 3a is formed by the subsequent reductive elimination and intramolecular annulation. Conclusion In conclusion, we have