- Solvent coordination to palladium can invert the selectivity of oxidative addition
-
Reaction solvent was previously shown to influence the selectivity of Pd/PtBu3-catalyzed Suzuki-Miyaura cross-couplings of chloroaryl triflates. The role of solvents has been hypothesized to relate to their polarity, whereby polar solvents stabilize anionic transition states involving [Pd(PtBu3)(X)]- (X = anionic ligand) and nonpolar solvents do not. However, here we report detailed studies that reveal a more complicated mechanistic picture. In particular, these results suggest that the selectivity change observed in certain solvents is primarily due to solvent coordination to palladium. Polar coordinating and polar noncoordinating solvents lead to dramatically different selectivity. In coordinating solvents, preferential reaction at triflate is likely catalyzed by Pd(PtBu3)(solv), whereas noncoordinating solvents lead to reaction at chloride through monoligated Pd(PtBu3). The role of solvent coordination is supported by stoichiometric oxidative addition experiments, density functional theory (DFT) calculations, and catalytic cross-coupling studies. Additional results suggest that anionic [Pd(PtBu3)(X)]- is also relevant to triflate selectivity in certain scenarios, particularly when halide anions are available in high concentrations.
- Elias, Emily K.,Neufeldt, Sharon R.,Rehbein, Steven M.
-
p. 1618 - 1628
(2022/02/21)
-
- Dual Photoredox-/Palladium-Catalyzed Cross-Electrophile Couplings of Polyfluoroarenes with Aryl Halides and Triflates
-
A visible-light photoredox-/Pd-catalyzed cross-electrophile arylation of polyfluoroarenes with aryl halides and triflates in the presence of dialkylamines is reported for the first time. This synergistic protocol affords access to a series of fluorodiaryls from easily available starting materials under mild and operationally simple conditions. A series of mechanistic experiments, including the stoichiometric reactions of a ligated (aryl)Pd complex, Stern-Volmer fluorescence quenching studies, cyclic voltammetry studies, and UV-vis spectroscopy, were performed to elucidate the potential catalytic pathway in this synergistic process.
- Qin, Jian,Zhu, Shengqing,Chu, Lingling
-
supporting information
p. 2246 - 2252
(2021/04/02)
-
- Nickel-Catalyzed Arylation/Alkenylation of tert-Cyclobutanols with Aryl/Alkenyl Triflates via a C - C Bond Cleavage
-
Herein, we first present a nickel-catalyzed arylation and alkenylation of tert-cyclobutanols with aryl/alkenyl triflates via a C-C bond cleavage. An array of γ-substituted ketones was obtained in moderate-to-good yields, thus featuring earth-abundant nick
- Wang, Zhen,Hu, Yuanyuan,Jin, Hongwei,Liu, Yunkui,Zhou, Bingwei
-
p. 466 - 474
(2020/12/22)
-
- Dynamic Kinetic Cross-Electrophile Arylation of Benzyl Alcohols by Nickel Catalysis
-
Catalytic transformation of alcohols via metal-catalyzed cross-coupling reactions is very important, but it typically relies on a multistep procedure. We here report a dynamic kinetic cross-coupling approach for the direct functionalization of alcohols. The feasibility of this strategy is demonstrated by a nickel-catalyzed cross-electrophile arylation reaction of benzyl alcohols with (hetero)aryl electrophiles. The reaction proceeds with a broad substrate scope of both coupling partners. The electron-rich, electron-poor, and ortho-/meta-/para-substituted (hetero)aryl electrophiles (e.g., Ar-OTf, Ar-I, Ar-Br, and inert Ar-Cl) all coupled well. Most of the functionalities, including aldehyde, ketone, amide, ester, nitrile, sulfone, furan, thiophene, benzothiophene, pyridine, quinolone, Ar-SiMe3, Ar-Bpin, and Ar-SnBu3, were tolerated. The dynamic nature of this method enables the direct arylation of benzylic alcohol in the presence of various nucleophilic groups, including nonactivated primary/secondary/tertiary alcohols, phenols, and free indoles. It thus offers a robust alternative to existing methods for the precise construction of diarylmethanes. The synthetic utility of the method was demonstrated by a concise synthesis of biologically active molecules and by its application to peptide modification and conjugation. Preliminary mechanistic studies revealed that the reaction of in situ formed benzyl oxalates with nickel, possibly via a radical process, is an initial step in the reaction with aryl electrophiles.
- Guo, Peng,Wang, Ke,Jin, Wen-Jie,Xie, Hao,Qi, Liangliang,Liu, Xue-Yuan,Shu, Xing-Zhong
-
supporting information
p. 513 - 523
(2021/01/12)
-
- Ni-Catalyzed Cross-Electrophile Coupling of Aryl Triflates with Thiocarbonates via C-O/C-O Bond Cleavage
-
A nickel-catalyzed reductive coupling of aryl triflates with thiocarbonates is reported here. Both electron-rich and -deficient aryl C(sp2)-O electrophiles as well as a class of O-tBu S-alkyl thiocarbonates are compatible with the optimized reaction conditions, as evidenced by 49 examples. The reaction also proceeds with good chemoselective cleavage of the C-O bond with regard to thioesters. This work broadens the scope of nickel-catalyzed reductive cross-electrophile coupling reactions.
- Zhu, Zhaodong,Gong, Yuxin,Tong, Weiqi,Xue, Weichao,Gong, Hegui
-
supporting information
p. 2158 - 2163
(2021/04/05)
-
- Palladium-Catalyzed Synthesis of N, N-Dimethylanilines via Buchwald-Hartwig Amination of (Hetero)aryl Triflates
-
This work delineates the synthesis of N,N-dimethylaniline derivatives from dimethylamines and aryl triflates. The palladium-catalyzed C-N bond formation proceeds in excellent yields, using an unsophisticated catalytic system, a mild base, and triflates as electrophiles, which are readily available from inexpensive phenols. N,N-Dimethylanilines are multifunctional reaction partners and represent useful but underutilized building blocks in organic synthesis.
- Pospech, Jola,Taeufer, Tobias
-
p. 7097 - 7111
(2020/06/27)
-
- Base-promoted selective O-phosphorylation of aryl triflates with P(O)-H compounds
-
Compared to previous transition metal-catalyzed C-phosphorylation reactions for constructing C–P bonds, in the absence of transition metal catalysts and ligands, a direct O-phosphorylation of aryl triflates selectively occurred with P(O)-H compounds in the presence of a base via the construction of O–P bonds. This transformation proceeds under simple and mild conditions, and provides a new method for the preparation of valuable organophosphoryl compounds from readily available P(O)-H compounds and triflates.
- Wang, Mingyue,Yang, Jia,Wang, Shuai,Zhong, Hong
-
supporting information
(2020/05/05)
-
- Palladium-Catalyzed Cyanation under Mild Conditions: A Case Study to Discover Appropriate Substrates among Halides and Pseudohalides
-
A case study has been effectively carried out to identify a suitable substrate among halides and pseudohalides for the palladium-catalyzed cyanation reactions under mild conditions. Among the various substrates considered for evaluation, aryl pentafluorobenzenesulfonates and nonaflates were identified to be the best substrates when compared to corresponding halides and pseudohalides. The substoichiometric use of nontoxic, environmentally benign potassium hexacyanoferrate as a cyanide source and exceptionally milder conditions further highlights the significance of the protocol developed. A wide range of electronically biased and sterically challenging substrates provided the corresponding the nitriles in good to excellent yields.
- Rajendra, Merla Arjuna,Sunil,Sajith, Ayyiliath Meleveetil,Joy, Muthipeedika Nibin,Bakulev, Vasiliy A.,Haridas, Karickal Raman
-
p. 1629 - 1633
(2020/09/15)
-
- Bismuth-Catalyzed Oxidative Coupling of Arylboronic Acids with Triflate and Nonaflate Salts
-
Herein we present a Bi-catalyzed cross-coupling of arylboronic acids with perfluoroalkyl sulfonate salts based on a Bi(III)/Bi(V) redox cycle. An electron-deficient sulfone ligand proved to be key for the successful implementation of this protocol, which allows the unusual construction of C(sp2)-O bonds using commercially available NaOTf and KONf as coupling partners. Preliminary mechanistic studies as well as theoretical investigations reveal the intermediacy of a highly electrophilic Bi(V) species, which rapidly eliminates phenyl triflate.
- Cornella, Josep,Peciukenas, Vytautas,Planas, Oriol
-
supporting information
p. 11382 - 11387
(2020/07/14)
-
- Reductive Coupling between C-N and C-O Electrophiles
-
The cross-electrophile reaction is a promising strategy for C-C bond formation. Recent studies have focused mainly on reactions with organic halides. Here we report a coupling reaction between C-N and C-O electrophiles that demonstrates the possibility of constructing a C-C bond via C-N and C-O cleavage. Several reactions between benzyl/aryl ammonium salts and vinyl/aryl C-O electrophiles have been studied. Preliminary mechanistic studies revealed that the benzyl ammoniums were activated through a radical mechanism.
- He, Rong-De,Li, Chun-Ling,Pan, Qiu-Quan,Guo, Peng,Liu, Xue-Yuan,Shu, Xing-Zhong
-
supporting information
p. 12481 - 12486
(2019/09/04)
-
- Transition-Metal-Free C-C, C-O, and C-N Cross-Couplings Enabled by Light
-
Transition-metal-catalyzed cross-couplings to construct C-C, C-O, and C-N bonds have revolutionized chemical science. Despite great achievements, these metal catalysts also raise certain issues including their high cost, requirement of specialized ligands, sensitivity to air and moisture, and so-called "transition-metal-residue issue". Complementary strategy, which does not rely on the well-established oxidative addition, transmetalation, and reductive elimination mechanistic paradigm, would potentially eliminate all of these metal-related issues. Herein, we show that aryl triflates can be coupled with potassium aryl trifluoroborates, aliphatic alcohols, and nitriles without the assistance of metal catalysts empowered by photoenergy. Control experiments reveal that among all common aryl electrophiles only aryl triflates are competent in these couplings whereas aryl iodides and bromides cannot serve as the coupling partners. DFT calculation reveals that once converted to the aryl radical cation, aryl triflate would be more favorable to ipso substitution. Fluorescence spectroscopy and cyclic voltammetry investigations suggest that the interaction between excited acetone and aryl triflate is essential to these couplings. The results in this report are anticipated to provide new opportunities to perform cross-couplings.
- Liu, Wenbo,Li, Jianbin,Querard, Pierre,Li, Chao-Jun
-
supporting information
p. 6755 - 6764
(2019/05/06)
-
- Palladium-Catalyzed Chemoselective Negishi Cross-Coupling of Bis[(pinacolato)boryl]methylzinc Halides with Aryl (Pseudo)Halides
-
We describe a palladium-catalyzed chemoselective Negishi cross-coupling of a bis[(pinacolato)boryl]methylzinc halide with aryl (pseudo)halides. This reaction affords an array of benzylic 1,1-diboronate esters, which can serve as useful synthetic handles f
- Lee, Hyojae,Lee, Yeosan,Cho, Seung Hwan
-
supporting information
p. 5912 - 5916
(2019/08/20)
-
- Synthesis of 2,2,5-Trisubstituted 2 H-Pyrroles and 2,3,5-Trisubstituted 1 H-Pyrroles by Ligand-Controlled Site-Selective Dearomative C2-Arylation and Direct C3-Arylation
-
Palladium-catalyzed site-selective dearomative C2-arylation of 2,5-diaryl-1H-pyrroles with aryl chlorides was accomplished, and a series of 2,2,5-triaryl-2H-pyrroles were synthesized. In addition, the site selectivity of the reaction was switched by simply changing the ligand, and the direct C3-arylated 2,3,5-triaryl-1H-pyrroles were prepared. The obtained 2,2,5-triaryl-2H-pyrroles could be further transformed into 2,2,5,5-tetraarylpyrrolidines.
- Yamaguchi, Miyuki,Fujiwara, Sakiko,Manabe, Kei
-
supporting information
p. 6972 - 6977
(2019/09/03)
-
- Reactions of Arylsulfonate Electrophiles with NMe4F: Mechanistic Insight, Reactivity, and Scope
-
This paper describes a detailed study of the deoxyfluorination of aryl fluorosulfonates with tetramethylammonium fluoride (NMe4F) and ultimately identifies other sulfonate electrophiles that participate in this transformation. 19F NMR spectroscopic monitoring of the deoxyfluorination of aryl fluorosulfonates revealed the rapid formation of diaryl sulfates under the reaction conditions. These intermediates can proceed to fluorinated products; however, diaryl sulfate derivatives bearing electron-donating substituents react very slowly with NMe4F. Based on these findings, aryl triflate and aryl nonaflate derivatives were explored, since these cannot react to form diaryl sulfates. Aryl triflates were found to be particularly effective electrophiles for deoxyfluorination with NMe4F, and certain derivatives (i.e., those bearing electron-neutral/donating substituents) afforded higher yields than their aryl fluorosulfonate counterparts. Computational studies implicate a similar mechanism for deoxyfluorination of all the sulfonate electrophiles.
- Schimler, Sydonie D.,Froese, Robert D. J.,Bland, Douglas C.,Sanford, Melanie S.
-
p. 11178 - 11190
(2018/09/12)
-
- Catalytic Alkyne Arylation Using Traceless Directing Groups
-
By using Pd0/Mandyphos, we achieved a three-component aminoarylation of alkynes to generate enamines, which are then hydrolyzed to either α-arylphenones or α,α-diarylketones. This Pd-catalyzed method overcomes established known pathways to enable the use of amines as traceless directing groups for C?C bond formation.
- Park, Jung-Woo,Kang, Bubwoong,Dong, Vy M.
-
supporting information
p. 13598 - 13602
(2018/09/25)
-
- A simple route to 1,4-addition reactions by Co-catalyzed reductive coupling of organic tosylates and triflates with activated alkenes
-
An efficient Co-catalyzed 1,4-addition reaction of alkyl/aryl triflates and tosylates with activated alkenes is described. In this reaction, an air-stable cobalt(ii) complex, a mild reducing agent Zn and a simple proton source (H2O) are used. A radical mechanism for the addition of alkyl tosylates to activated alkenes is likely involved.
- Hsieh, Jen-Chieh,Chu, Yi-Hua,Muralirajan, Krishnamoorthy,Cheng, Chien-Hong
-
supporting information
p. 11584 - 11587
(2017/10/27)
-
- Copper-Catalyzed C-S Bond Formation via the Cleavage of C-O Bonds in the Presence of S8 as the Sulfur Source
-
Useful and applicable methods for one-pot and odorless synthesis of unsymmetrical and symmetrical diaryl sulfides via C-O bond activation are presented. First, a new efficient procedure for the synthesis of unsymmetrical sulfides using the cross-coupling reaction of phenolic esters such as acetates, tosylates, and triflates and with arylboronic acid or triphenyltin chloride as the coupling partners is reported. Depending on the reaction, S 8 /KF or S 8 /NaO t -Bu system is found to be an effective source of sulfur in the presence of copper salts and in poly(ethylene glycol) as a green solvent. Then, the synthesis of symmetrical diaryl sulfides from phenolic compounds by using S 8 as the sulfur source and NaO t -Bu in anhydrous DMF at 120 °C under N 2 is described. By these protocols, the synthesis of a variety of unsymmetrical and symmetrical sulfides become easier than the available protocols in which thiols and aryl halides are directly used for the preparation of the sulfides.
- Rostami, Abed,Rostami, Amin,Ghaderi, Arash,Gholinejad, Mohammad,Gheisarzadeh, Sajedeh
-
p. 5025 - 5038
(2017/10/06)
-
- Copper-Catalyzed Regioselective C-H Sulfonyloxylation of Electron-Rich Arenes with p-Toluenesulfonic Acid and Sulfonyloxylation of Aryl(mesityl)iodonium Sulfonates
-
Copper-catalyzed regioselective C-H sulfonyloxylation of electron-rich arenes with p-toluenesulfonic acid has been developed. Electron-rich benzene derivatives and heteroarenes can undergo this C-H sulfonyloxylation reaction to generate aryl tosylates. Furthermore, sulfonyloxylation of aryl(mesityl)iodonium sulfonates has also been investigated. Both aryl(mesityl)iodonium tosylates and triflates can react smoothly to get aryl sulfonates. The formed aryl sulfonates can be converted to phenols, as well as used as good partners of cross-coupling reactions.
- Huang, He,Wu, Yang,Zhang, Wen,Feng, Chun,Wang, Bi-Qin,Cai, Wan-Fei,Hu, Ping,Zhao, Ke-Qing,Xiang, Shi-Kai
-
p. 3094 - 3101
(2017/03/23)
-
- Nickel-catalyzed phosphorylation of aryl triflates with P([Formula presented] compounds
-
A nickel-catalyzed phosphorylation of aryl triflates with P([Formula presented] compounds is disclosed. This reaction can proceed smoothly under a mild reaction condition, producing the corresponding aryl phosphorus compounds in good to high yields.
- Yang, Jia,Xiao, Jing,Chen, Tieqiao,Han, Li-Biao
-
p. 120 - 124
(2016/08/23)
-
- Copper-Catalyzed Enantioselective 1,6-Boration of para-Quinone Methides and Efficient Transformation of gem-Diarylmethine Boronates to Triarylmethanes
-
Presented is the first enantioselective copper-catalyzed 1,6-conjugate addition of bis(pinacolato)diboron to para-quinone methides. The reaction proceeds with excellent yields and good to excellent enantioselectivities, and provides an attractive approach to the construction of optically active gem-diarylmehtine boronic esters. Additionally, the subsequent conversion of the derived potassium trifluoroborates into triarylmethanes with highly enantiospecificity was realized.
- Lou, Yazhou,Cao, Peng,Jia, Tao,Zhang, Yongling,Wang, Min,Liao, Jian
-
supporting information
p. 12134 - 12138
(2015/10/12)
-
- Selective arylation and vinylation at the α position of vinylarenes
-
In intermolecular Heck reactions of styrene and vinylarenes, the aryl and vinyl groups routinely insert at the β position. However, selective insertion at the α position has been very rare. Herein, we provide a missing piece in the palette of Heck reaction, which gave >20:1 α selectivity. The key to our success is a new ferrocene 1,1′-bisphosphane (dnpf) that carries 1-naphthyl groups. Our mechanistic studies revealed that the high α selectivity is partly attributable to the steric effect of dnpf. The rigid and bulky 1-naphthyl groups of dnpf sterically disfavor β insertion. What the Heck! In intermolecular Heck reactions, insertion at the β position of aromatic olefins is very common, but reversal of the selectivity for selective α insertion has been a longstanding problem. A general method to couple aryl and vinyl triflates with aromatic olefins in >20:1 α selectivity is presented. The key to this successful approach is a new ferrocene bisphosphane with naphthyl groups on the phosphorus atom (see scheme; OTf=triflate). Copyright
- Zou, Yinjun,Qin, Liena,Ren, Xinfeng,Lu, Yunpeng,Li, Yongxin,Zhou, Jianrong
-
supporting information
p. 3504 - 3511
(2013/07/05)
-
- Achieving vinylic selectivity in Mizoroki-heck reaction of cyclic olefins
-
In Heck reactions of cyclic olefins, the products usually have aryl groups that end up at the allylic and/or homoallylic position. We herein report new selectivity that adds aryl groups to the vinylic position. Cyclic olefins of various ring size worked well. The desired isomers were produced by palladium-hydride-catalyzed isomerization of the initial products. Thus, a specific catalyst must be used so that it can perform two jobs under one set of reaction conditions. Copyright
- Wu, Xiaojin,Lu, Yunpeng,Hirao, Hajime,Zhou, Jianrong
-
supporting information
p. 6014 - 6020
(2013/06/26)
-
- Scope of direct arylation of fluorinated aromatics with aryl sulfonates
-
The scope and limitations of direct arylation of fluorinated aromatics with aryl sulfonates was examined. Pd(OAc)2, in the presence of MePhos and KOAc in THF, efficiently catalyzed the direct arylation of fluoro aromatics with aryl triflates un
- Chang, Joyce Wei Wei,Chia, Eugene Yurong,Chai, Christina Li Lin,Seayad, Jayasree
-
supporting information; experimental part
p. 2289 - 2299
(2012/04/10)
-
- Regioselectivity switch achieved in the palladium catalyzed α-arylation of enones by employing the modified Kuwajima-Urabe conditions
-
A new regioselective approach to the synthesis of α-aryl enones is reported. This represents an important application of the Kuwajima-Urabe protocol toward the synthesis of this simple albeit complex functional array. Several α-aryl enones were synthesized by the palladium catalyzed arylation of triethylsilylenol ethers of enones with high regioselectivity and broad scope, utilizing sterically encumbered electron-rich phosphine ligands to drive the reaction.
- Kale, Ajit Prabhakar,Pawar, Govind Goroba,Kapur, Manmohan
-
supporting information; experimental part
p. 1808 - 1811
(2012/06/18)
-
- Low-Temperature Ag/Pd-catalyzed decarboxylative cross-coupling of aryl trflates with aromatic carboxylate salts
-
Chemical Equation Presented At 50°C lower than the best known copper catalysts, a catalytic silver(I)/ palladium(II) system allows the decarboxylative cross-coupling of arenecarboxylates with aryl triflates at temper-atures as low as 120°C. Remarkably, polychlorinated and many heterocyclic arenecarboxylates are converted for the first time in high yields. FG = functional group.
- Goossen, Lukas J.,Lange, Paul P.,Rodriguez, Nuria,Linder, Christophe
-
supporting information; experimental part
p. 3906 - 3909
(2010/07/03)
-
- Biaryl and aryl ketone synthesis via Pd-catalyzed decarboxylase coupling of carboxylate salts with aryl triflates
-
A bimetallic catalyst system has been developed that for the first time allows the decarboxylative crosscoupling of aryl and acyl carboxylates with aryl triflates. In contrast to aryl halides, these electrophiles give rise to non-coordinating anions as byproducts, which do not interfere with the decarboxylation step that leads to the generation of the carbon nucleophilic crosscoupling partner. As a result, the scope of carboxylate substrates usable in this transformation was extended from ortho-substituted or otherwise activated derivatives to a broad range of ortho-, meta-, and para-substituted aromatic carboxylates. Two alternative protocols have been optimized, one involving heating the substrates in the presence of CuI/1,10- phenanthroline (10-15 mol %) and PdI2/phosphine (23 mol%) in NMP for 1-24 h, the other involving CuI/l,10-phenanthroline (615mol%) and PdBr2/Tol-BINAP (2 mol % ) in NMP using microwave heating for 5-10 min. While most products are accessible using standard heating, the use of microwave irradiation was found to be beneficial especially for the conversion of non-activated carboxylates with functionalized aryl triflates. The synthetic utility of the transformation is demonstrated with 48 examples showing the scope and limitations of both protocols. In mechanistic studies, the special role of microwave irradiation is elucidated, and further perspectives of decarboxylase crosscouplings are discussed.
- Goossen, Lukas J.,Linder, Christophe,Rodriguez, Nuria,Lange, Paul P.
-
supporting information; experimental part
p. 9336 - 9349
(2010/04/03)
-
- Decarboxylative biaryl synthesis from aromatic carboxylates and aryl triflates
-
A new catalyst system, generated in situ from Cu2O, 1,10-phenanthroline, PdI2, and Tol-BINAP, for the first time allows the decarboxylative coupling of carboxylic acids with aryl triflates. In contrast to previous decarboxylative couplings that remained limited to certain activated carboxylates, e.g., ortho-substituted benzoates, this halide-free protocol is generally applicable to aromatic carboxylic acid salts regardless of their substitution pattern. Copyright
- Goossen, Lukas J.,Rodriguez, Nuria,Linder, Christophe
-
supporting information; experimental part
p. 15248 - 15249
(2009/03/11)
-
- The conversion of phenols to the corresponding aryl halides under mild conditions
-
Mild, novel procedures have been developed for the syntheses of aryl halides from the corresponding phenols in modest to good yields via boronate ester intermediates.
- Thompson, Alicia L. S.,Kabalka, George W.,Akula, Murthy R.,Huffman, John W.
-
p. 547 - 550
(2007/10/03)
-
- A polystyrene-supported triflating reagent for the synthesis of aryl triflates
-
An insoluble polystyrene-supported triflating reagent has been prepared by suspension co-polymerization of N-(4-vinylphenyl)trifluoromethanesulphonimide, styrene and the JandaJel cross-linker. This reagent, in the presence of triethylamine, allows for the efficient synthesis of aryl triflates from a wide range of phenols in a process that permits the desired product to be isolated from the reaction mixture in essentially pure form via several filtration and concentration operations. Adding to the utility of this reagent is its ability to be easily recovered, regenerated and reused. Both soluble and insoluble bifunctional polymers containing trialkylamine moieties in addition to triflimide groups were also prepared and examined as triflating reagents. Unfortunately these reagents afforded only modest yields of the desired products in representative reactions. Graphical Abstract.
- Chung, Cecilia Wan Ying,Toy, Patrick H.
-
p. 709 - 715
(2007/10/03)
-
- The sequel to a carbocyclic nucleoside synthesis: A divergent access to both arenediazonium ions and aryl triflates
-
Depending on the amount of acid used, treating aryl-dialkyl triazenes of general structure 3 with triflic acid resulted in the formation of either the corresponding arenediazonium triflates 4 or aryl triflates 8 apparently by two different pathways, the latter conversion being favoured at high acid concentration.
- Picherit,Wagner,Uguen
-
p. 2579 - 2583
(2007/10/03)
-
- Practical Synthesis of Aryl Triflates under Aqueous Conditions
-
A practical and efficient synthesis of aryl triflates under biphasic basic aqueous conditions is described. The current methodology provides entry into these valuable substrates that omits the use of amine bases and allows facile isolation by s
- Frantz, Doug E.,Weaver, Damian G.,Carey, James P.,Kress, Michael H.,Dolling, Ulf H.
-
p. 4717 - 4718
(2007/10/03)
-
- Hypervalent silane and siloxane derivatives and the use thereof
-
Hypervalent silane and siloxane reagents (preformed or generated in situ) for transmetalation in palladium catalyzed reactions with derivatives of allylic alcohols, aryl halides, electron-withdrawing aryl bromides, and aryl triflates derived from phenols are disclosed. Also disclosed are methods of preparing glycosyl azides by reaction of an azide with a silyl ester in the presence of a phoshine.
- -
-
-
- Fluorination of aromatic compounds from 1-aryl-3,3-dimethyltriazenes and fluoride anions in acidic medium: 1. A model for 18F labelling
-
Decomposition of 1-aryl-3,3-dialkyltriazenes by strong and non-nucleophilic acids (CF3SO3H, H2SO4) can be achieved at 90°C in carbon tetrachloride, in the presence of sub-stoichiometric amounts of fluoride anions. Yields of fluoroarenes up to 39% (versus F-) can be reached under these conditions, within 15-30min and without contamination of the fluorinated compounds by inseparable by-products. Such conditions and results enable an adaptation to radiofluorination with 18F-.
- Pages, Thierry,Langlois, Bernard R.
-
p. 321 - 327
(2007/10/03)
-
- Synthesis of unsymmetrical biaryls by palladium-catalyzed cross coupling reactions of arenes with tetrabutylammonium triphenyldifluorosilicate, a hypervalent silicon reagent
-
Palladium-catalyzed cross coupling of arenes with tetrabutylammonium triphenyldifluorosilicate, a hypervalent silicon reagent, to give unsymmetrical biaryls is reported. The Pd(0)-catalyzed process proceeds in good yield with aryl iodides, most aryl trifiates, and electron-deficient aryl bromides.
- Mowery, Molly E.,DeShong, Philip
-
p. 3266 - 3270
(2007/10/03)
-
- Nickel- and Palladium-Catalyzed Homocoupling of Aryl Triflates. Scope, Limitation, and Mechanistic Aspects
-
Whereas the direct reduction of aryl triflates affords mainly phenols and some arenes, the presence of a catalytic amount of palladium or nickel results in the formation of biaryls. The homocoupling is performed in the presence of an electron source, either a cathode or zinc powder. A judicious choice of the metal (nickel or palladium), the ligand (monodentate or bidentate phosphine), and the reduction process (electrochemical or chemical) allows the synthesis of functional symmetrical biaryls. Nickel and palladium complexes ligated by bidentate ligands such as NiCl2(dppf) and Pd(OAc)2 + 1 BINAP are very efficient for the homocoupling of 1-naphthyl triflate, since the dimer was obtained in almost quantitative yield. However, the homocoupling is sensitive to steric hindrance, excluding for the moment the synthesis of atropisomers. The homocoupling proceeds via an activation of the C - O bond of the aryl triflate by a palladium(0) (or a nickel(0)) complex, providing an intermediate arylpalladium(II) (or nickel(II)) complex that after activation by electron transfer affords a new complex able to undergo a second oxidative addition with the aryl triflates.
- Jutand, Anny,Mosleh, Adil
-
p. 261 - 274
(2007/10/03)
-
- New multi-coupling benzylic zinc reagents for the preparation of flexible aromatic compounds
-
The benzylic zinc reagents 3a-c bearing a triflate group in o-, m- or p-position are new efficient multi-coupling reagents reacting stepwise with an aryl iodide (Ar1-I) and an arylzinc bromide (Ar2ZnBr) in the presence of the appropriate palladium catalyst and the suitable phosphine ligand leading to polyfunctional flexible aromatic products of type 5. This methodology is appropriate for applications in combinatorial chemistry.
- Rottlaender, Mario,Knochel, Paul
-
p. 1749 - 1752
(2007/10/03)
-
- A Facile Preparation of Aryl Triflates. Decomposition of Arenediazonium Tetrafluoroborate Salts in Trifluoromethanesulfonic Acid
-
The thermal or photochemical decomposition of arenediazonium tetrafluoroborate salts n trifluoromethanesulfonic acid, with or without organic bases such as pyridine, provides aryl triflates in high yields.
- Yoneda, Norihiko,Fukuhara, Tsuyoshi,Mizokami, Takao,Suzuki, Akira
-
p. 459 - 460
(2007/10/02)
-
- Palladium Catalysed Alkoxycarbonylation of Phenols to Benzoate Esters
-
The methoxycarbonylation of aryl trifluoromethanesulphonates with CO and aliphatic alcohols is catalysed by Pd(OAc)2-1,3-bis(diphenylphosphino)propane in high yield at 70 deg C and ambient CO pressure.
- Dolle, Roland E.,Schmidt, Stanley J.,Kruse, Lawrence I.
-
p. 904 - 905
(2007/10/02)
-
- Reaction of Triflates with Potassium Diethyl Phosphite. Formation of Phosphate Esters
-
Phenyl triflate and substituted analogues react with potassium diethyl phosphite in liquid ammonia to form aryl diethyl phosphate esters.The reaction formally involves loss of trifluoromethanesulfinate ion from the triflate and concomitant oxidation of phosphorus to the phosphate stage.Preliminary data suggest that, in a series of triflates, reactivity follows the order aryl > cyclohexenyl > cyclopropyl > alkyl.Studies on aryl triflates with added labeled phenoxide rule out a mechanism involving free phenoxide ion, i.e., displacement of phenoxide by nucleophilic attack of diethyl phosphite ion on sulfur followed by phosphorylation of displaced phenoxide.Three potential mechanisms, including one involving initial attack of phosphorus at sulfur, a biphilic insertion mechanism, and one involving nucleophilic attack on oxygen, are suggested, all of which could account for these observations.
- Creary, Xavier,Benage, Brigitte,Hilton, Kathryn
-
p. 2887 - 2891
(2007/10/02)
-