Copper-mediated arylation with arylboronic acids: Facile and modular synthesis of triarylmethanes

• H. Surya Prakash Rao and
• A. Veera Bhadra Rao

Beilstein J. Org. Chem. 2016, 12, 496–504, doi:10.3762/bjoc.12.49

• above observations, we propose a mechanism for the copper-mediated coupling of phenylboronic acid with diphenylmethanol, leading to triphenylmethane and boric acid (Scheme 3). At the start of the cascade, the first step is the transmetallation of the copper(II) into phenylboronic acid to form reactive

Synthesis and structures of ruthenium–NHC complexes and their catalysis in hydrogen transfer reaction

• Chao Chen,
• Chunxin Lu,
• Qing Zheng,
• Shengliang Ni,
• Min Zhang and
• Wanzhi Chen

Beilstein J. Org. Chem. 2015, 11, 1786–1795, doi:10.3762/bjoc.11.194

• , China 10.3762/bjoc.11.194 Abstract Ruthenium complexes [Ru(L1)2(CH3CN)2](PF6)2 (1), [RuL1(CH3CN)4](PF6)2 (2) and [RuL2(CH3CN)3](PF6)2 (3) (L1= 3-methyl-1-(pyrimidine-2-yl)imidazolylidene, L2 = 1,3-bis(pyridin-2-ylmethyl)benzimidazolylidene) were obtained through a transmetallation reaction of the

Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF₅-substituted phenylboronic esters and iodobenzenes

• George Iakobson,
• Junyi Du,
• Alexandra M. Z. Slawin and
• Petr Beier

Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162

• proceeded in satisfactory yields considering the electron-deficient character of the boronates and consequently less efficient transmetallation step (Scheme 4). Transformation to SF5-phenylboronic acid 8b and potassium trifluoroborates 9 was straightforward under standard conditions (Scheme 5). Similar

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

• with the generation of the related transition state or formation of [ArPdLn][XAgmY] with a highly electrophilic cation and subsequent transmetallation with the weakly nucleophilic borate. Efficiency of AgmY as a polarizing agent decreases in order Ag2O > AgNO3 ≈ Ag2SO4 > Ag[BF4] > AgF. No clear

• Ag2O and assumed the generation of a hydroxy–palladium complex with higher ability to transmetallation under the action of the corresponding organoboron reagent than ArPdL2X. For example, complex trans-C6F5Pd(PEt3)2OH is formed in the reaction of trans-C6F5Pd(PEt3)2I with Ag2O in toluene–water and

• 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

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• by the addition of an aqueous base. According to their discussion, the aqueous base converted the Rh(acac) complex to the corresponding RhOH complex. Such RhOH complexes have been proposed in the literature as active intermediates in the transmetallation of organoboronic acids [122][144][145]. Scheme

(2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-Mono(di,tri)fluoromethylcyclopropyl]alanines and their incorporation into hormaomycin analogues

• Armin de Meijere,
• Sergei I. Kozhushkov,
• Dmitrii S. Yufit,
• Christian Grosse,
• Marcel Kaiser and
• Vitaly A. Raev

Beilstein J. Org. Chem. 2014, 10, 2844–2857, doi:10.3762/bjoc.10.302

• (including a transmetallation), the (2S,3R)-3-methyl-3-phenylalanine required for hormaomycin and its analogues, has previously been utilized [9][54][55]. In view of the good performance of the Belokoń protocol for various electrophilic reagents it appeared attractive to apply it for the synthesis of β

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

• substitution patterns were used, giving access to a variety of alkenylphosphines 71a via this method. If a more sterically hindered substrate ((α-substituted alkenyl)zirconocene) or reagent (iPr2PCl) is used, a transmetallation of Zr(IV) to Cu(I) is necessary for the reaction in order to proceed (Scheme 18

• , under similar conditions (Scheme 25) [53]. The reaction was catalyzed by NiCl2(dppe) in the presence of zinc. The role of zinc was to reduce Ni(II) to Ni(0) and to form Ph2PZnCl for the transmetallation step. Kazankova and co-workers have explored the catalysts (Ph3P)2NiCl2 and Ni(acac)2 for the

Molecular recognition of isomeric protonated amino acid esters monitored by ESI-mass spectrometry

• Andrea Liesenfeld and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 825–831, doi:10.3762/bjoc.10.78

• started from 1-bromo-4-methoxybenzene which was transferred into 2-bromo-4’-methoxybiphenyl (3) in 92% yield via lithiation with t-BuLi, transmetallation with zinc(II) bromide, and subsequent Negishi cross-coupling reaction with 1-bromo-2-iodobenzene [14][15]. 3 was then transformed into the corresponding

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

A new manganese-mediated, cobalt-catalyzed three-component synthesis of (diarylmethyl)sulfonamides

• Antoine Pignon,
• Erwan Le Gall and
• Thierry Martens

Beilstein J. Org. Chem. 2014, 10, 425–431, doi:10.3762/bjoc.10.39

• was previously established that zinc is able to reduce cobalt(II) in the presence of an aryl halide to promote the formation of a transient arylcobalt(II) species, which undergoes a fast transmetallation with zinc to furnish an organozinc species [39]. It can thus be assumed that a reductive metal

• other than zinc, e.g., manganese, can also promote a similar process. The first reaction step is the manganese-mediated formation of the organocobalt intermediate I. Depending on the kinetics of the transmetallation of I by manganese salts, two different scenarios may be envisaged featuring either an

• organocobalt or an organomanganese species as the key organometallic II. In the first scenario, manganese undergoes a slow transmetallation with the organocobalt species I. It has been shown earlier that zinc salts undergo rapid transmetallations with organocobalt(II) species to furnish organozinc compounds

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

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

• Mikko Passiniemi and
• Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

• diastereoselectivity was observed. Peter Wipf has done pioneering work on the hydrozirconation–transmetallation sequence [78][79]. Murakami used this information when investigating the reaction of transmetallated 1-(E)-pentadecenylzirconocene chloride with (S)-1 [46][47]. When the reaction was performed in THF at 0 °C

• inverted, and the anti-adduct 49 was favoured (12:1 anti/syn). We have also been interested in the use of hydrozirconation–transmetallation process while working on the synthesis of galactonojirimycin (Scheme 21) [48]. We used the TBS-protected propargyl alcohol 31 as the nucleophile, which had been

• investigated by Negishi for the hydrozirconation–transmetallation process [80]. Our findings were in agreement with the results of Murakami. High syn-selectivity (>1:20 anti/syn) was achieved in CH2Cl2 with Et2Zn as the transmetallating agent. The reaction could also be performed in toluene, but the

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• reacted with Selectfluor and PhB(OH)2 (ii). Moreover, Ph3PAuCl and PhB(OH)2 were mixed together, no formation of Ph3PAuPh was detected ruling out the transmetallation as initial stage of the catalytic cycle (iii). In addition, Ph3PAuPh proved to be a competent catalyst of the process but only in the

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• mechanism remains to be elucidated, the authors presume that the reaction proceeds via generation of CuCF3 followed by transmetallation with the arylboronic acid. The diamine stabilizes the CuCF3 species. This facilitates the oxidation to Cu(II) or Cu(III) species which undergo facile reductive elimination

• Cu(I) to Cu(II) under photoexcitation. Both products then combine to afford a Cu(III)CF3 species, which undergoes transmetallation with the arylboronic acid. Finally, reductive elimination from Cu(III)(aryl)(CF3) affords the desired aryl-CF3 product (Figure 11 and Table 26). M. Beller et al

• . investigated the copper-catalyzed trifluoromethylation of aryl and vinyl boronic acids with in situ generated CF3-radicals using NaSO2CF3 (Table 27 and Table 28) [97]. The CF3 radical is generated from the reaction of TBHP (t-BuOOH) with NaSO2CF3. Transmetallation of the arylboronic acid with the Cu(II

Cu-catalyzed trifluoromethylation of aryl iodides with trifluoromethylzinc reagent prepared in situ from trifluoromethyl iodide

• Yuzo Nakamura,
• Motohiro Fujiu,
• Tatsuya Murase,
• Yoshimitsu Itoh,
• Hiroki Serizawa,
• Kohsuke Aikawa and
• Koichi Mikami

Beilstein J. Org. Chem. 2013, 9, 2404–2409, doi:10.3762/bjoc.9.277

• products in moderate to high yields. The advantage of this method is that additives such as metal fluoride (MF), which are indispensable to activate silyl groups for transmetallation in the corresponding reactions catalyzed by copper salt by using the Ruppert–Prakash reagents (CF3SiR3), are not required

• solid, can also be used for the trifluoromethylation of aryl iodides, while stoichiometric amounts of copper(I) bromide are required to afford the more reactive trifluoromethyl copper (CuCF3) species by transmetallation [13][14]. However, these reagents are generally prepared from trifluoromethyl

• Schlenk equilibrium with Zn(CF3)2 and ZnI2 [14][24] was prepared in situ from CF3I and Zn dust in 60–80% yields in both solvents. The addition of CuI (0.2 equiv) to a DMPU solution of Zn(CF3)I led to the transmetallation of the CF3 group from zinc to copper even at room temperature. Two singlet peaks of

Synthesis, characterization and luminescence studies of gold(I)–NHC amide complexes

• Adrián Gómez-Suárez,
• David J. Nelson,
• David G. Thompson,
• David B. Cordes,
• Duncan Graham,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2013, 9, 2216–2223, doi:10.3762/bjoc.9.260

• for the synthesis of such species using hydroxide 1: a) via transmetallation from either boronic acids or siloxides, or b) via deprotonation reactions of suitable substrates. We have applied the latter methodology to the synthesis of organogold–NHC complexes bearing several trans-ligands, such as

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• of alkyne 50 with Schwartz’s reagent [54][55] was followed by transmetallation to zinc and nonselective addition into aldehyde 47. Oxidation of the resulting allylic alcohol mixture afforded the enone 53. Prior to the key oxy-Michael addition, it was necessary to remove the tert-butyldimethylsilyl

Coupling of C-nitro-NH-azoles with arylboronic acids. A route to N-aryl-C-nitroazoles

• Marta K. Kurpet,
• Aleksandra Dąbrowska,
• Małgorzata M. Jarosz,
• Katarzyna Kajewska-Kania,
• Nikodem Kuźnik and
• Jerzy W. Suwiński

Beilstein J. Org. Chem. 2013, 9, 1517–1525, doi:10.3762/bjoc.9.173

• ]. It involves several steps: transmetallation of boronic acid with a catalyst, coordination of the azole molecule to the Cu(II) species followed by oxidation of copper(II) into copper(III) in the presence of oxygen, and then reductive elimination releasing the product and Cu(I) complex. A regeneration

Regio- and stereoselective carbometallation reactions of N-alkynylamides and sulfonamides

• Yury Minko,
• Morgane Pasco,
• Helena Chechik and
• Ilan Marek

Beilstein J. Org. Chem. 2013, 9, 526–532, doi:10.3762/bjoc.9.57

• species. To improve the chemical yield of this transformation, we considered the copper-catalyzed carbomagnesiation reaction. However, such catalytic reaction requires a transmetallation reaction of the intermediate vinylcopper into vinylmagnesium halide, and due to the intramolecular chelation, it is

Radical zinc-atom-transfer-based carbozincation of haloalkynes with dialkylzincs

• Fabrice Chemla,
• Florian Dulong,
• Franck Ferreira and
• Alejandro Pérez-Luna

Beilstein J. Org. Chem. 2013, 9, 236–245, doi:10.3762/bjoc.9.28

• carbenoids are multipurpose reagents [47] that are typically prepared from 1,1'-dihaloalkenes, either by lithium/halogen exchange followed by transmetallation with zinc salts or by direct zinc/halogen exchange [48][49][50]. Alternatively, they can also be prepared efficiently by selective monohalogenation of

Intramolecular carbolithiation of N-allyl-ynamides: an efficient entry to 1,4-dihydropyridines and pyridines – application to a formal synthesis of sarizotan

• Wafa Gati,
• Mohamed M. Rammah,
• Mohamed B. Rammah and
• Gwilherm Evano

Beilstein J. Org. Chem. 2012, 8, 2214–2222, doi:10.3762/bjoc.8.250

• isolated in modest yields (30–33%), even in the presence of additional HMPA, which might may constitute the major limitation of our process. Other attempts involving electrophiles such as acid chlorides and allyl bromide or transmetallation with zinc chloride and Negishi cross-coupling were unsuccessful

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

• ]. Various chloroformates and imines can participate in this reaction, stannanes being limited to aryl, benzyl or ethyl ones. When vinylstannane was used, the transmetallation step was more rapid than the CO insertion, giving instead substituted carbamates. After removal of the solvents in vacuo, the

• novel strategy, dedicated to the synthesis of indenamines 14, involves addition of an electron-rich palladium/phosphine complex to a triple bond, followed by nucleophilic addition to an iminium ion generated in situ by addition of a secondary amine to an aldehyde. Transmetallation of the resulting

Selectivity in C-alkylation of dianions of protected 6-methyluridine

• Ngoc Hoa Nguyen,
• Christophe Len,
• Anne-Sophie Castanet and
• Jacques Mortier

Beilstein J. Org. Chem. 2011, 7, 1228–1233, doi:10.3762/bjoc.7.143

• (evaluated by NMR) with exclusive deuterium incorporation at the C6 position. However, almost complete recovery of the starting material was observed when dianion 11 was allowed to react with 4-bromobut-1-ene [15]. Lithium–copper transmetallation was also attempted. Unfortunately, addition of 0.25 equiv of

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

• equatorial position, placing the electronegative carbamate substituent and the C–O bond in the tetrahydropyran ring into a gauche orientation (Figure 1). We propose a chelated transition state for the formation of 19, 21, and 23 (Scheme 3). After the initial hydrozirconation and transmetallation with

Continuous flow enantioselective arylation of aldehydes with ArZnEt using triarylboroxins as the ultimate source of aryl groups

• Julien Rolland,
• Xacobe C. Cambeiro,
• Carles Rodríguez-Escrich and
• Miquel A. Pericàs

Beilstein J. Org. Chem. 2009, 5, No. 56, doi:10.3762/bjoc.5.56

• flow system for the synthesis of enantioenriched diarylmethanols from aldehydes is described. The system uses an amino alcohol-functionalized polystyrene resin as the catalyst, and the arylating agent is conveniently prepared by transmetallation of triarylboroxins with diethylzinc. Keywords

• have been explored as the ultimate source of aryl groups [24][25][26][27][28][29]. In these approaches generally good results have been obtained, but at the expense of using a large excess of diethylzinc for the transmetallation step, since two non-productive equivalents of the reagent are consumed in

• to be used in the reaction [30][31][32] (Scheme 2). This represents a highly atom-economical approach since, in principle, no sacrificial excess of diethylzinc is needed for the transmetallation process and up to a 74% of the molecular mass of triphenylboroxin (the less favourable example) can be