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

Pd(OAc)₂-catalyzed dehydrogenative C–H activation: An expedient synthesis of uracil-annulated β-carbolinones

• Biplab Mondal,
• Somjit Hazra,
• Tarun K. Panda and
• Brindaban Roy

Beilstein J. Org. Chem. 2015, 11, 1360–1366, doi:10.3762/bjoc.11.146

• a seven membered palladacycle B which in turn produces the product β-carbolinones after reductive elimination from the 7-membered palladacycle B. The catalytic cycle is completed by AgOAc. Conclusion In conclusion we have developed an elegant method for the preparation of uracil annulated β

Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• situ to the transient diene by reductive elimination using naked iodide [37][38][39] or the iodo-ionic liquid 1-butyl-3-methylimidazolium iodide [40]. After purification by column chromatography on silica gel, we noted that complete aromatization has occurred concomitantly and molecular clip 4 was

Hydrogenation of unactivated enamines to tertiary amines: rhodium complexes of fluorinated phosphines give marked improvements in catalytic activity

• Sergey Tin,
• Tamara Fanjul and
• Matthew L. Clarke

Beilstein J. Org. Chem. 2015, 11, 622–627, doi:10.3762/bjoc.11.70

• significantly [14]. DFT calculations revealed that in the hydrogenation of these aldehyde-derived enamines, the final stage of hydrogenation, reductive elimination was the rate-determining step. This is in contrast to nearly all studies on homogeneous hydrogenation of alkenes where oxidative addition, and

• hydrogenated faster. A possible reason for the enamine 1f being reduced slower than 1g may come from the fact that 1f is a much more stable enamine (see enamine synthesis section, Supporting Information File 1). It is well known that the reductive elimination is sped up with more bulky ligands – i.e., when the

• issue with the strong π-acceptor ligand triphenylphosphite. We note here that an earlier attempt by some of us using chiral phosphites in this type of reaction gave very low conversions to product under these conditions. The ligand electronic effect clearly supports our earlier proposal of the reductive

Weakly nucleophilic potassium aryltrifluoroborates in palladium-catalyzed Suzuki–Miyaura reactions: relative reactivity of K[4-RC₆F₄BF₃] and the role of silver-assistance in acceleration of transmetallation

• Vadim V. Bardin,
• Anton Yu. Shabalin and
• Nicolay Yu. Adonin

Beilstein J. Org. Chem. 2015, 11, 608–616, doi:10.3762/bjoc.11.68

• undergoes transmetallation with 4-MeOC6H4B(OH)2 [21]. The subsequent reductive elimination leads to the corresponding polyfluorobiphenyl. In contrary, the reaction of trans-C6F5Pd(PEt3)2I with 2,4,6-C6F3H2B(OH)2 and Ag2O leads to an unsymmetrical diarylpalladium complex trans-(C6F5)Pd(PEt3)2(2,4,6-C6F3H2

• neutral complex ArPdX by the oxidative addition of ArX to Pd(0) species. This step precedes the subsequent transformation of ArPdX and does not influence the reactivity of organoboron partner K[4-RC6F4BF3] as well as its behavior in transmetallation and/or reductive elimination steps. For the further

• . There is a popular notion that the transmetallation gives both cis- and trans-ArPdLnAr'. First of them is low stable and undergoes easy reductive elimination to biphenyl. trans-ArPdLnAr' can react only after transformation to the corresponding cis-isomer [40][41]. Complexes with polyfluorinated aryl

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• (II) complex is oxidized by silver(I) ions to Cu(III) complex 18, and the C–O bond is formed via reductive elimination. The drawbacks of this method are the use of large amounts of silver triflate and alcohol and the high temperature of the reaction. The Pd(OAc)2/persulfate system was used in the

• reductive elimination to give product 235 (Scheme 49) [217]. The Pd(OAc)2·[1,2-bis(phenylsulfinyl)ethane]-catalyzed enantioselective acetoxylation of terminal alkenes was accomplished in the presence of a chiral Lewis acid; ee = 45–63%; the reaction was performed with a small excess of AcOH (1.1 equiv) in

• ligand facilitates the reductive elimination of the allyl ester from the π-allyl–palladium intermediate [220]. Linear E-allyl acetates were synthesized also by the acetoxylation of terminal alkenes with the PdCl2/NaOAc/AcOH/O2 system (5 atm) in N,N-dimethylacetamide [221]. The Wacker reaction giving

Sequential decarboxylative azide–alkyne cycloaddition and dehydrogenative coupling reactions: one-pot synthesis of polycyclic fused triazoles

• Kuppusamy Bharathimohan,
• Thanasekaran Ponpandian,
• A. Jafar Ahamed and
• Nattamai Bhuvanesh

Beilstein J. Org. Chem. 2014, 10, 3031–3037, doi:10.3762/bjoc.10.321

• reductive elimination reaction yields the polycyclic triazoles 4. Conclusion In summary, we have successfully developed an efficient and convenient one-pot protocol for the synthesis of novel benzimidazole and imidazole-fused 1,2,3-triazoloquinoxaline derivatives. The key finding of this work is the

Palladium-catalysed cyclisation of alkenols: Synthesis of oxaheterocycles as core intermediates of natural compounds

• Miroslav Palík,
• Jozef Kožíšek,
• Peter Koóš and
• Tibor Gracza

Beilstein J. Org. Chem. 2014, 10, 2077–2086, doi:10.3762/bjoc.10.216

• formed from σ-alkyl PdII-complexes F and G by reductive elimination of Pd0 (Scheme 6). Additionally, the X-ray analysis [44] of 53 confirmed the absolute configuration and structure of the six-membered heterocycle (Figure 4). Recently, Wolfe reported a tetrahydrofuran-forming reaction via Pd-catalysed

Synthesis of ethoxy dibenzooxaphosphorin oxides through palladium-catalyzed C(sp²)–H activation/C–O formation

• Seohyun Shin,
• Dongjin Kang,
• Woo Hyung Jeon and
• Phil Ho Lee

Beilstein J. Org. Chem. 2014, 10, 1220–1227, doi:10.3762/bjoc.10.120

• PhI(OAc)2. However, no cyclized product was observed. This result indicates that the C–O reductive elimination from Pd(II) is not favorable. Because both the intermolecular and intramolecular competition experiments exhibited no significant kinetic isotope effect (kH/kD = 1.0 and 0.6; Scheme 8), we

• hypothesize that the C–O reductive elimination step is the rate-determining step. A feasible mechanism involving the Pd(II)/Pd(IV) catalytic cycle is described in Scheme 9. The C–H activation might be efficiently accelerated by the N–H activation propelled by N-Ac-L-Leu-OH (L9) as a ligand [53][54][55

• ], resulting in the formation of palladacycle III. Thereafter, ethoxy dibenzooxaphosphorin oxide 2a is obtained from the oxidation of the Pd(II) to Pd(IV) species IV and the subsequent C–O reductive elimination. Conclusion In this paper, we have developed an efficient synthetic method for a wide range of

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• diphenylphosphine to α,β-unsaturated ketones [127][128], esters [129], sulfonic esters [130] or to dienones [131]. The proposed mechanism is ubiquitous in metal-catalyzed hydrophosphination involving a P–H oxidative addition, insertion of the olefin into the Pd–H bond and reductive elimination. In 2007 several

Synthesis of (2S,3R)-3-amino-2-hydroxydecanoic acid and its enantiomer: a non-proteinogenic amino acid segment of the linear pentapeptide microginin

• Rajendra S. Rohokale and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2014, 10, 667–671, doi:10.3762/bjoc.10.59

• multicomponent condensation reactions of aldehyde, an amine and ketene silyl acetal derivatives to get the vicinal hydroxylamino acids [17]. In addition, a few strategies employ a chiral pool approach. For example, Wee et al. utilized the zinc-silver-mediated reductive elimination of α-D-lyxofuranosyl

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• moiety, which is coupled by transmetallation with the alkyne 6 and reductive elimination to give the ynylideneindolone intermediate 11. The ynylideneindolone 11 is a vinylogous Michael system, and therefore, it is reasonable to assume a 1,4-addition of the nucleophilic enamine 12, which is employed

Zirconoarylation of alkynes through p-chloranil-promoted reductive elimination of arylzirconates

• Xiaoyu Yan,
• Chao Chen and
• Chanjuan Xi

Beilstein J. Org. Chem. 2014, 10, 528–534, doi:10.3762/bjoc.10.48

• /bjoc.10.48 Abstract A novel method for the zirconoarylation of alkynes was developed. TCQ-promoted reductive elimination of arylzirconate [LiCp2ZrAr(RC≡CR)], which was prepared by the reaction of zirconocene–alkyne complexes with aryllithium compounds, afforded trisubstituted alkenylzirconocenes. This

• reaction can afford multi-substituted olefins with high stereoselectivity. Keywords: alkyne; multicomponent; reductive elimination; zirconate; zirconoarylation; Introduction The controlled synthesis of multi-substituted olefins is one of the most challenging tasks in organic synthesis [1][2]. A series of

• to fulfill arylzirconation of alkynes (Scheme 2). Recently, we have reported a p-chloranil (TCQ)-promoted reductive elimination reaction of the zirconate complex Li[Cp2Zr(C≡CR)3] toward geminal enediynes [44]. As part of our ongoing project on organozirconate chemistry [45][46][47][48], we envisioned

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

Practical synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides via conventional and decarboxylative copper-free Sonogashira coupling reactions

• Andrea Caporale,
• Stefano Tartaggia,
• Andrea Castellin and
• Ottorino De Lucchi

Beilstein J. Org. Chem. 2014, 10, 384–393, doi:10.3762/bjoc.10.36

• acetylene after reductive elimination. The activated acetylide species for the coupling process is generated from the reaction of a terminal alkyne with copper in the presence of a base and is transferred on the palladium site via transmetallation. In order to improve the efficacy of the reaction, several