Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• indanones (Scheme 4) [59]. Phenylrhodation of 1g first proceeds to form 1A. A subsequent intramolecular 1,4-hydrogen shift gives 1B, which smoothly undergoes an intramolecular 1,4-addition to yield 1C. Finally, transmetalation from the phenylzinc reagent to rhodium enolate 1C affords zinc enolate 1h, which

• afford 2B or 2C (Scheme 8). Further transmetalation of vinyliron intermediate 2B or 2C with R′MgBr yielded the corresponding vinylmagnesium intermediate 2D. Therefore, selective synthesis of both regioisomers of allylic alcohols can be accomplished by simply choosing transition-metal catalysts (Cu or Fe

• exchange and the subsequent transmetalation to zinc, and then used directly in one pot (Table 3). Lautens reported enantioselective carbozincation of alkenes using a palladium catalyst with a chiral ligand (Scheme 23) [93]. Treatment of 3g with diethylzinc in the presence of catalytic amounts of palladium

Stereoselective synthesis of tetrasubstituted alkenes via a sequential carbocupration and a new sulfur–lithium exchange

• Andreas Unsinn,
• Cora Dunst and
• Paul Knochel

Beilstein J. Org. Chem. 2012, 8, 2202–2206, doi:10.3762/bjoc.8.248

• iodolysis leading to the iodide 10 in 93% yield. Treatment of 1,2-dibromobenzene with iPrMgCl·LiCl at −15 °C for 2 h followed by a transmetalation with ZnCl2 gives the required zinc reagent 11, which undergoes a Negishi cross-coupling with the iodide 10 at 50 °C (5 h) leading to the alkynyl thioether 1a in

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

• favours the formation of the 2-stannyloxazole, which is isolated as the major product and then successfully engaged in Stille cross-coupling reactions with various (hetero)aryliodides and bromides [28][29][30]. The subsequent transmetalation reaction following lithiation with zinc dichloride also favours

• analysis [35]. Nevertheless, subsequent cross-coupling reactions under palladium catalysis were successfully achieved. Similarly to the Passerini reaction, it was hypothesized that the crucial transmetalation step proceeds throught a nucleophilic displacement of the halogen from the σ-arylpalladium complex

• ]. The resulting C2-carbanion may be in equilibrium with a stabilized carbene intermediate and finally reacts with copper iodide to give the organocopper intermediate. Bellina and Rossi also noted that this last transmetalation step may be complicated by a second, well-known equilibrium of the 2

Pseudo five-component synthesis of 2,5-di(hetero)arylthiophenes via a one-pot Sonogashira–Glaser cyclization sequence

• Dominik Urselmann,
• Dragutin Antovic and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2011, 7, 1499–1503, doi:10.3762/bjoc.7.174

• halogen–metal exchange, transmetalation and isolation occasionally turns out to be tedious and in many cases the use of polar functionality in the substrate is considerably restricted. In recent years interesting examples of palladium-catalyzed direct C–H activation and arylation of (hetero)aromatics have

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

• block the ring closure (Scheme 12) [11]. Homoallylic amines and α-aminoesters 24 were prepared by Malinakova and coworkers, by a palladium(II)-catalyzed coupling of boronic acids, 1,2-nonadiene, and aliphatic, aromatic or heteroaromatic imines [12]. The authors postulated a transmetalation step between

• another allenic unit. After a new transmetalation step with the boronic acid, the active catalytic species can be released and entered into a new catalytic cycle (Scheme 13). Imine as a nucleophilic partner A tandem four-component reaction allowing access to 1,2-dihydroisoquinolin-1-ylphosphonates 26 was

Directed ortho,ortho'-dimetalation of hydrobenzoin: Rapid access to hydrobenzoin derivatives useful for asymmetric synthesis

• Inhee Cho,
• Labros Meimetis,
• Lee Belding,
• Michael J. Katz,
• Travis Dudding and
• Robert Britton

Beilstein J. Org. Chem. 2011, 7, 1315–1322, doi:10.3762/bjoc.7.154

• copper or iron halides [31], or palladium(II)chloride [32] were unsuccessful. In an effort to fine-tune the procedure by attenuating the reactivity of the tetralithio intermediate 8, transmetalation with ZnCl2 or MgBr2 followed by treatment with various electrophiles was also investigated

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• iPrMgCl·LiCl (64) at −40 °C for 1 h leading to an intermediate magnesium reagent, which after transmetalation to the corresponding zinc reagent using ZnBr2 provides, after Negishi cross-coupling reaction with the bromoquinoline 80, the polyfunctinal triazene 81 in 75% yield. The conversion of the triazene

• preparation of a CDK inhibitor, purvalanol A (84). Thus, an I/Mg-exchange on the purine 85 with iPrMgCl·LiCl (64), followed by the transmetalation to the corresponding copper derivative with CuCl·2LiCl, and the addition of the lithiated aniline derivative 86, furnishes the amidocuprate 87. In the presence of

• reaction of these Grignard reagents and transmetalation to zinc organometallics with ZnCl2 affords the expected products 101, 104 and 107 in 69–82% (Scheme 17 and Supporting Information File 1, Procedure 6) [9][22]. 2.3 Preparation of polyfunctional heterocyclic magnesium reagents by directed magnesation

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

The role of silver additives in gold-mediated C–H functionalisation

• Scott R. Patrick,
• Ine I. F. Boogaerts,
• Sylvain Gaillard,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2011, 7, 892–896, doi:10.3762/bjoc.7.102

• achieved. The high electronegativity of the silver counter ion is of great importance. Finally, evidence of an interaction between silver salts and the substrate suggests that silver activates the aryl C–H bond and is then implicated in a transmetalation reaction with gold to provide the product. The value

Homoallylic amines by reductive inter- and intramolecular coupling of allenes and nitriles

• Peter Wipf and
• Marija D. Manojlovic

Beilstein J. Org. Chem. 2011, 7, 824–830, doi:10.3762/bjoc.7.94

• Peter Wipf Marija D. Manojlovic Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA 15260, USA 10.3762/bjoc.7.94 Abstract The one-pot hydrozirconation of allenes and nitriles followed by an in situ transmetalation of the allylzirconocene with dimethylzinc or zinc

• chloride provides functionalized homoallylic amines. An intramolecular version of this process leads to 3-aminotetrahydrofurans and 3-aminotetrahydropyrans. Keywords: allene; 3-aminotetrahydrofurans; 3- and 4-aminotetrahydropyrans; hydrozirconation; nitrile; transmetalation; Introduction The reversible

• ][9]. Similar to the related alkyl- and alkenyl- zirconocenes [1][2][3][6], this limitation of sterically hindered allylzirconocene complexes can be overcome by selective transmetalation of zirconium to other metals. Suzuki and co-workers treated allylzirconocenes with methylaluminoxane (MAO) in order

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• in quantitative yields with an excellent regioisomeric ratio (8a/8b = 98/2, Scheme 5). The nature of the alkyl group of the dialkylzinc species can be broadened since it could also be prepared in-situ by a transmetalation reaction of RMgX with half equivalent of a zinc salt. The scope of the reaction

• (−40 instead of −78 °C), which can be attributed to a slow copper to magnesium contrathermodynamic transmetalation reaction, probably due to a strong intramolecular chelation of the sp2 organometallic derivative by the carbamate moiety. N-substituted alkynes Nitrogen-substituted alkynes (ynamine

A short and efficient synthesis of valsartan via a Negishi reaction

• Samir Ghosh,
• A. Sanjeev Kumar and
• G. N. Mehta

Beilstein J. Org. Chem. 2010, 6, No. 27, doi:10.3762/bjoc.6.27

• , the use of organozinc compounds provides better transmetalation activity than that obtained by the use of organoboron reagents as well as good chemoselectivity since most common functional groups are not attacked by organozinc species. Although preparations of several biphenyl ring systems related to

Mechanistic aspects of the isomerization of Z-vinylic tellurides double bonds in the synthesis of potassium Z-vinyltrifluoroborate salts

• Hélio A. Stefani,
• Rafael C. Guadagnin,
• Artur F. Keppler,
• Giancarlo V. Botteselle,
• João V. Comasseto and
• Carlos A. Suganuma

Beilstein J. Org. Chem. 2008, 4, No. 9, doi:10.1186/1860-5397-4-9

• , Universidade de São Paulo, São Paulo, Brazil 10.1186/1860-5397-4-9 Abstract Through direct transmetalation reaction of Z-vinylic tellurides with nBuLi was observed the unexpected isomerization of double bonds leading to potassium E-vinyltrifluoroborates salts in low to moderate yields. Using EPR spin trapping

A convenient catalyst system for microwave accelerated cross- coupling of a range of aryl boronic acids with aryl chlorides

• Matthew L. Clarke,
• Marcia B. France,
• Jose A. Fuentes,
• Edward J. Milton and
• Geoffrey J. Roff

Beilstein J. Org. Chem. 2007, 3, No. 18, doi:10.1186/1860-5397-3-18

• ). Buchwald and co-workers have previously noted the failure of 2,4,6-trifluorophenyl boronic acid to react with aryl chlorides, although the origin of this effect was not identified. The origin of this low reactivity could be due to slow transmetalation, [35][36][37][38] homo-coupling problems,[39] or Pd

• understanding, stoichiometric experiments between [Pd(dppf)Cl2] and boronic acids were carried out (Scheme 4). Given that [Pd(dppf)(Ar)2] species rapidly reductively eliminate,[41] successful transmetalation should result in significant amounts of the symmetrical biaryl (alongside a number of other species such