Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• ) intermediate XII. The subsequent selective coordination of the arene generates the complex XIII, which in turn undergoes reductive elimination providing the final product and a Pd(0) species. The reoxidation of the latter giving the active Pd(II) catalyst completes the catalytic cycle. In addition to the

• agent in the presence of different nucleophiles suitable to generate the σ-alkyl-palladium complexes, which give the final products 54 by reductive elimination. The amide of 2-indolecarboxylic acid bearing two allylic groups (55) undergoes a domino process with generation of the tetracyclic product 56

Metal–ligand multiple bonds as frustrated Lewis pairs for C–H functionalization

• Matthew T. Whited

Beilstein J. Org. Chem. 2012, 8, 1554–1563, doi:10.3762/bjoc.8.177

• eliminations frequently utilized to generate such multiply bonded units. The limitations of these sorts of reactions in terms of potential catalytic applications are largely related to the reluctance of the metal center to undergo redox chemistry (e.g., N–C reductive elimination to generate an amine). The

• systems are constructed to favor high oxidation states, so reductive elimination is quite unfavorable relative to other non-redox processes, and insertion of unsaturated bonds is generally not observed. In a sense, this limitation is similar to what is encountered in attempts to use σ-bond metathesis

• the types of reactivity discussed thus far, there are several distinct routes to the functionalization of C–H (or E–H) bonds using metal–ligand multiply bonded FLPs. If C–H activation is effected by 1,2-addition across a M═E bond, then reductive elimination could result in a net C–H insertion of

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• by the isonitrile function, leading to the ring-close aryloxazol-2-yl palladium complex delivering products after a final reductive elimination step (Scheme 3). Catalytic direct (hetero)arylation of (benz)oxazoles Palladium- and/or copper-catalyzed direct (hetero)arylation with halides: Synthetic

• -arylated benzoxazole after a reductive elimination step (Scheme 19a). Deuterium-incorporation experiments and DFT calculations highly support this pathway as well as the successful palladium-catalyzed arylation of the O-silylated 2-isonitrilephenolate (Scheme 19b). Last year, Strotman and Chobanian

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• characterized. When vinyltributyltin was added as a third component in the reaction medium, a transmetallation step occurred, followed by a reductive elimination step, furnishing amides 2 in good to excellent yields [2]. This reaction tolerated various functional groups on the imine moiety, such as ether

• species with a boronic acid or triethylborane, followed by a reductive elimination, afforded the indenamine core in good to excellent yields. However, this Pd-catalyzed cyclization was only effective for aldehydes since ketones did not participate in the process (Scheme 6). Tsukamato extended this

• cyclofunctionalization of the allyl moiety by carbopalladation/reductive elimination [22]. It is interesting to note that 3-sulfonylpyrolidin-2-ones (γ-lactams) 48 may also be accessed in high yield as single trans-diastereomers upon simple treatment of N-allyl- or N-methylpyrrolidines with 2-mercaptobenzoic acid in

Combination of gold catalysis and Selectfluor for the synthesis of fluorinated nitrogen heterocycles

• Antoine Simonneau,
• Pierre Garcia,
• Jean-Philippe Goddard,
• Virginie Mouriès-Mansuy,
• Max Malacria and
• Louis Fensterbank

Beilstein J. Org. Chem. 2011, 7, 1379–1386, doi:10.3762/bjoc.7.162

• explained either by direct fluorination of the enamine resulting from the gold-promoted alkyne hydroamination or by oxidation of the intermediate vinyl gold(I) complex by Selectfluor into a gold(III) fluoride species followed by a reductive elimination. Moreover, the formation of C(sp2)–F bonds, either by

• on compounds 1a,b in a 5- and 6-exo-dig manner, respectively, and reductive elimination occurring at a vinyl gold(III) fluoride species or bimolecular fluorodeauration (Scheme 2). We also anticipated from this study to gain more insight into the reactivity of gold catalysts/Selectfluor combinations

• nucleophilic attack by the NH moiety. The resulting σ-vinyl Au(III) intermediate C could undergo a reductive elimination of its σ-vinyl and F ligands to give 2a, or a protodeauration leading to pyrrolidine 6, which would also rapidly isomerize into 7. Both 6 and 7 under the given reaction conditions would

A practical microreactor for electrochemistry in flow

• Kevin Watts,
• William Gattrell and
• Thomas Wirth

Beilstein J. Org. Chem. 2011, 7, 1108–1114, doi:10.3762/bjoc.7.127

• , be used in similar reaction pathways, and are beneficial for organic synthesis due to their low toxicity and cost [20]. Iodonium salts are currently being used in three main types of reactions, namely ligand exchange, reductive elimination and ligand coupling. This is due to their highly electron

Homocoupling of aryl halides in flow: Space integration of lithiation and FeCl₃ promoted homocoupling

• Aiichiro Nagaki,
• Yuki Uesugi,
• Yutaka Tomida and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2011, 7, 1064–1069, doi:10.3762/bjoc.7.122

• transmetalation of the aryl group from lithium to iron followed by reductive elimination of the homo-coupling product seems to be plausible, while a similar mechanism is proposed for homo-coupling of organomagnesium compounds with FeCl3 [19][20]. The regiospecificity of the coupling is consistent with this

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• for the addition to alkenes. The experimental studies suggest that the C–C bond-forming reaction occurs through a bimolecular reductive elimination. Furthermore, a gold-catalyzed three-component coupling was also developed for the oxidative oxyarylation of alkenes 358 via a similar strategy [170

Au(I)/Au(III)-catalyzed Sonogashira-type reactions of functionalized terminal alkynes with arylboronic acids under mild conditions

• Deyun Qian and
• Junliang Zhang

Beilstein J. Org. Chem. 2011, 7, 808–812, doi:10.3762/bjoc.7.92

• ]. Finally, D undergoes reductive elimination to give the desired product and gold(I) species A. In addition, C also could experience a five-centered transition state D', which leads to the C–C bond-forming reaction through a bimolecular reductive elimination [30][31][32]. Notably, we believed that the key

Synthesis of cross-conjugated trienes by rhodium-catalyzed dimerization of monosubstituted allenes

• Tomoya Miura,
• Tsuneaki Biyajima,
• Takeharu Toyoshima and
• Masahiro Murakami

Beilstein J. Org. Chem. 2011, 7, 578–581, doi:10.3762/bjoc.7.67

• -head manner to form the five-membered rhodacyclic intermediate A [22][23][24][25], which is in equilibrium with another rhodacyclic intermediate B via σ–π–σ isomerization. Then, β-hydride elimination takes place with B to form rhodium hydride C stereoselectively. Finally, reductive elimination from C

• reductive elimination. Under the optimized reaction conditions using dppe as the ligand, various monosubstituted allenes 1b–j were subjected to the catalytic dimerization reaction (Table 2). In most cases, essentially one isomer 3 was formed, and the other isomer 2 was barely detectable in the 1H NMR

Rh(I)-catalyzed intramolecular [2 + 2 + 1] cycloaddition of allenenes: Construction of bicyclo[4.3.0]nonenones with an angular methyl group and tricyclo[6.4.0.0^1,5]dodecenone

• Fuyuhiko Inagaki,
• Naoya Itoh,
• Yujiro Hayashi,
• Yumi Matsui and
• Chisato Mukai

Beilstein J. Org. Chem. 2011, 7, 404–409, doi:10.3762/bjoc.7.52

• spiro[4.5]deca-1,6-diene system via β-elimination and subsequent reductive elimination [31][32]. In summary, we have developed the intramolecular Rh(I)-catalyzed PKTR between 1,1-disubstituted allene and 1,1-disubstituted alkene functionalities, which leads to the facile formation of bicyclo[4.3.0

C–C (alkynylation) vs C–O (ether) bond formation under Pd/C–Cu catalysis: synthesis and pharmacological evaluation of 4-alkynylthieno[2,3-d]pyrimidines

• Dhilli Rao Gorja,
• K. Shiva Kumar,
• K. Mukkanti and
• Manojit Pal

Beilstein J. Org. Chem. 2011, 7, 338–345, doi:10.3762/bjoc.7.44

• on the surface of the charcoal. Once generated, the organo-Pd(II) species E then facilitates the stepwise formation of C–C bond via (i) trans organometallation with copper acetylide generated in situ from CuI and the terminal alkyne followed by (ii) reductive elimination of Pd(0) to afford 4

Rh-Catalyzed rearrangement of vinylcyclopropane to 1,3-diene units attached to N-heterocycles

• Franca M. Cordero,
• Carolina Vurchio,
• Stefano Cicchi,
• Armin de Meijere and
• Alberto Brandi

Beilstein J. Org. Chem. 2011, 7, 298–303, doi:10.3762/bjoc.7.39

• bond to form the intermediates C which can undergo metal hydride elimination or 1,3-hydride migration to the rhodium to give, respectively, the allyl- and alkylrhodium(III) hydride complexes D and F. Metal extrusion by reductive elimination leads to the observed dienes and regeneration of the catalyst

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• • radical generated from CF3I [40]. However, the reaction with bench-stable Togni’s reagent is mechanistically distinct from the previous radical approach (Scheme 34). In accord with a similar mechanism proposed by Togni [37], the resulting λ3-iodane species 40 undergo rapid reductive elimination with

C-Arylation reactions catalyzed by CuO-nanoparticles under ligand free conditions

• Mazaahir Kidwai,
• Saurav Bhardwaj and
• Roona Poddar

Beilstein J. Org. Chem. 2010, 6, No. 35, doi:10.3762/bjoc.6.35

• . The observed decrease in reactivity in the order p-nitroiodobenzene > iodobenzene > p-methyliodobenzene > 1-iodo-4-methoxybenzene suggests that the reaction proceeds by oxidative addition followed by reductive elimination. In addition to this, the order of reactivity suggests that aryl halides having

An exceptional P-H phosphonite: Biphenyl- 2,2'-bisfenchylchlorophosphite and derived ligands (BIFOPs) in enantioselective copper- catalyzed 1,4-additions

• T. Kop-Weiershausen,
• J. Lex,
• J.-M. Neudörfl and
• B. Goldfuss

Beilstein J. Org. Chem. 2005, 1, No. 6, doi:10.1186/1860-5397-1-6

• ligands (L*) exhibit large steric demands and good metal to ligand back bonding abilities. Such ligands generate active R-CuI-L* catalysts and support the rate determining reductive elimination in the catalytic cycle (Scheme 1). [42][43][44][45][46][47] Common basis for diol-based phosphoramidites and

• -rich transition metals, such as CuI. The rate determining reductive elimination was expected to be favored by the good metal to ligand back bonding properties of the σ*(P-Cl) acceptor as is well established in phosphites, i.e. σ*(P-OR), and phosphoramidites, i.e. σ*(P-NR2). Computed anharmonic CO