- Lewis Acidity Scale of Diaryliodonium Ions toward Oxygen, Nitrogen, and Halogen Lewis Bases
-
Equilibrium constants for the associations of 17 diaryliodonium salts Ar2I+X- with 11 different Lewis bases (halide ions, carboxylates, p-nitrophenolate, amines, and tris(p-anisyl)phosphine) have been investigated by titrations followed by photometric or conductometric methods as well as by isothermal titration calorimetry (ITC) in acetonitrile at 20 °C. The resulting set of equilibrium constants KI covers 6 orders of magnitude and can be expressed by the linear free-energy relationship lg KI = sI LAI + LBI, which characterizes iodonium ions by the Lewis acidity parameter LAI, as well as the iodonium-specific affinities of Lewis bases by the Lewis basicity parameter LBI and the susceptibility sI. Least squares minimization with the definition LAI = 0 for Ph2I+ and sI = 1.00 for the benzoate ion provides Lewis acidities LAI for 17 iodonium ions and Lewis basicities LBI and sI for 10 Lewis bases. The lack of a general correlation between the Lewis basicities LBI (with respect to Ar2I+) and LB (with respect to Ar2CH+) indicates that different factors control the thermodynamics of Lewis adduct formation for iodonium ions and carbenium ions. Analysis of temperature-dependent equilibrium measurements as well as ITC experiments reveal a large entropic contribution to the observed Gibbs reaction energies for the Lewis adduct formations from iodonium ions and Lewis bases originating from solvation effects. The kinetics of the benzoate transfer from the bis(4-dimethylamino)-substituted benzhydryl benzoate Ar2CH-OBz to the phenyl(perfluorophenyl)iodonium ion was found to follow a first-order rate law. The first-order rate constant kobs was not affected by the concentration of Ph(C6F5)I+ indicating that the benzoate release from Ar2CH-OBz proceeds via an unassisted SN1-type mechanism followed by interception of the released benzoate ions by Ph(C6F5)I+ ions.
- Legault, Claude Y.,Mayer, Robert J.,Mayr, Herbert,Ofial, Armin R.
-
supporting information
(2020/03/13)
-
- Cu(II)-catalyzed C-N coupling of (hetero)aryl halides and N-Nucleophiles promoted by α-benzoin oxime
-
We first reported the new application of a translate metal chelating ligand α-benzoin oxime for improving Cu-catalyzed C-N coupling reactions. The system could catalyse coupling reactions of (hetero)aryl halides with a wide of nucleophiles (e.g., azoles, piperidine, pyrrolidine and amino acids) in moderate to excellent yields. The protocol allows rapid access to the most common scaαolds found in FDA-approved pharmaceuticals.
- Yuan, Chunling,Zhang, Lei,Zhao, Yingdai
-
-
- Methyl-α-d-glucopyranoside as Green Ligand for Selective Copper-Catalyzed N-Arylation
-
In the selective N-arylation of amines or azoles with aryl halidesa-, methyl-α-d-glucopyranoside (MG) was found to function as a green ligand of copper powder. In addition, nitrogen heterocyclic amine compounds can also undergo the N-arylation coupling with heterocyclic aryl chlorides. This process allows access to a variety of aromatic amines and aryl azoles under mild reaction conditions, has good tolerance, and proceeds in moderate to high yield.
- Chen, Fengyang,Chen, Guoliang,Chen, Yuanguang,Du, Fangyu,Zhou, Qifan
-
p. 4590 - 4600
(2019/12/11)
-
- Structures, Lewis Acidities, Electrophilicities, and Protecting Group Abilities of Phenylfluorenylium and Tritylium Ions
-
The isolation, characterization, and the first X-ray structures of a fluorenylium ion and its Lewis adducts with nitrogen- and phosphorus-centered Lewis bases are reported. Kinetics of the reactions of a series of fluorenylium ions with reference π-, σ-, and n-nucleophiles of various sizes and nucleophilicities allowed the interplay between electronic and structural parameters on the electrophilicities of these planarized tertiary carbenium ions to be elucidated. Structure–reactivity correlations and extensive comparisons of their reactivities with those of di- and triarylcarbenium ions are described. Quantitative determination of the electrofugalities of fluorenylium ions revealed to which extent they are complementing tritylium ions as protecting groups and how their tuning is possible. Determination of the equilibrium constants of the Lewis adducts formation between pyridines of calibrated Lewis basicities and phenylfluorenylium and tritylium ions allowed the determination of their Lewis acidities and to showcase the potential of these carbon-centered Lewis acids in catalysis.
- Follet, Elsa,Mayer, Peter,Berionni, Guillaume
-
supporting information
p. 623 - 630
(2017/01/18)
-
- Lewis acid activation of pyridines for nucleophilic aromatic substitution and conjugate addition
-
A clean, mild and sustainable method for the functionalization of pyridines and their analogues is reported. A zinc-based Lewis acid is used to activate pyridine and its analogues towards nucleophilic aromatic substitution, conjugate addition, and cyclization reactions by binding to the nitrogen on the pyridine ring and activating the pyridine ring core towards further functionalization.
- Abou-Shehada, Sarah,Teasdale, Matthew C.,Bull, Steven D.,Wade, Charles E.,Williams, Jonathan M. J.
-
p. 1083 - 1087
(2015/03/30)
-
- Room-temperature dissociation of 1,2-dibromodisilenes to bromosilylenes
-
A room-temperature dynamic equilibrium between dibromodisilenes and bromosilylenes has been demonstrated by taking advantage of the steric protection using the fused-ring bulky 1,1,3,3,5,5,7,7-octa-R-s-hydrindacen-4-yl (Rind) groups. Although the bromosilylenes cannot be directly observed by spectroscopic methods, the thermal homolytic cleavage of the Si=Si double bond has been confirmed by a pseudo-first-order kinetics for the trapping with bis(trimethylsilyl)acetylene and a crossover reaction using two kinds of Rind-substituted dibromodisilenes. The addition of 4-pyrrolidinopyridine (PPy) to the dibromodisilene leads to an equilibrium mixture between the dibromodisilene and a PPy adduct of bromosilylene, the latter being isolated and characterized. The substitution of the bromine atom in the dibromodisilene by the Grignard reagent is significantly accelerated by the addition of PPy.
- Suzuki, Katsunori,Matsuo, Tsukasa,Hashizume, Daisuke,Tamao, Kohei
-
supporting information; experimental part
p. 19710 - 19713
(2012/01/13)
-
- Structure-activity relationship study of EphB3 receptor tyrosine kinase inhibitors
-
A structure-activity relationship study for a 2-chloroanilide derivative of pyrazolo[1,5-a]pyridine revealed that increased EphB3 kinase inhibitory activity could be accomplished by retaining the 2-chloroanilide and introducing a phenyl or small electron donating substituents to the 5-position of the pyrazolo[1,5-a]pyridine. In addition, replacement of the pyrazolo[1,5-a]pyridine with imidazo[1,2-a]pyridine was well tolerated and resulted in enhanced mouse liver microsome stability. The structure-activity relationship for EphB3 inhibition of both heterocyclic series was similar. Kinase inhibitory activity was also demonstrated for representative analogs in cell culture. An analog (32, LDN-211904) was also profiled for inhibitory activity against a panel of 288 kinases and found to be quite selective for tyrosine kinases. Overall, these studies provide useful molecular probes for examining the in vitro, cellular and potentially in vivo kinase-dependent function of EphB3 receptor.
- Qiao, Lixin,Choi, Sungwoon,Case, April,Gainer, Thomas G.,Seyb, Kathleen,Glicksman, Marcie A.,Lo, Donald C.,Stein, Ross L.,Cuny, Gregory D.
-
supporting information; experimental part
p. 6122 - 6126
(2010/06/16)
-
- Synthesis of aminopyridines via an unprecedented nucleophilic aromatic substitution of cyanopyridines
-
The direct reaction of 2- and 4-cyanopyridines with lithium amides affords good yields of the corresponding aminopyridines via displacement of cyanide. Addition of CsF accelerates the reaction and can lead to significantly higher yields.
- Penney, Jonathan M.
-
p. 2667 - 2669
(2007/10/03)
-
- Microwave assisted solvent free amination of halo-(pyridine or pyrimidine) without transition metal catalyst
-
A solvent free direct amination of halo-(pyridine or pyrimidine) has been developed in good to high yields under computer-controlled microwave irradiation without transition metal catalyst. This reaction is a solvent and metal free, useful method for coupling of halo-(pyridine or pyrimidine) with pyrrolidine and piperidine derivatives by nucleophilic aromatic substitution (SNAr).
- Narayan, Sanjay,Seelhammer, Troy,Gawley, Robert E.
-
p. 757 - 759
(2007/10/03)
-
- Nickel-catalysed amination of aryl chlorides using a dihydroimidazoline carbene ligand
-
A new arylamination protocol has been developed using a catalyst combination prepared from Ni(acac)2 associated to a sterically hindered dihydroimidazoline carbene ligand. A high efficiency was attained using, in most cases, only 2 mol% Ni/carbene clusters.
- Gradel, Benot,Brenner, Eric,Schneider, Rapha?l,Fort, Yves
-
p. 5689 - 5692
(2007/10/03)
-
- A new facile method for the synthesis of 4-dialkylaminopyridine derivatives by high-pressure-promoted amination of 4-chloropyridine
-
A new method for synthesizing 4-(di)alkylaminopyridine derivatives in high yield was established by the high-pressure-promoted nucleophilic aromatic substitution of 4-chloropyridine with various primary/secondary amines.
- Kotsuki, Hiyoshizo,Sakai, Hiromitsu,Shinohara, Toshio
-
p. 116 - 118
(2007/10/03)
-
- NEW APPLICATION OF COMPLEX BASES: NUCLEOPHILIC CONDENSATIONS OF PYRIDINE
-
3,4-Dehydropyridine can be easily generated from 3-bromopyridine by complex bases.Nucleophilic condensations of amines, ketones and nitrile enolates are thus performed for the first time in good to very good yields.
- Jamart-Gregoire, Brigitte,Leger, Christian,Caubere, Paul
-
p. 7599 - 7602
(2007/10/02)
-
- Borane-Methyl Sulfide Reductive Cyclization of ω-Ester Alkylamides: A Convenient Synthesis of N-Substituted Cyclic Amines
-
Borane-methyl sulfide (BMS) reduction of variously N-substituted succinamic and glutaramic esters affords the corresponding N-substituted pyrrolidines and piperidines in high yields.The limitations, mainly caused by steric hinderance around the amine nitrogen, and putative intermediates involved in this conversion, as detected by incomplete reaction and/or synthesis followed by BMS reduction, indicate that cyclization and amide reduction successfully compete with ester reduction to afford the N-substituted cyclized amines.
- Venuti, Michael C.,Ort, Oswald
-
p. 985 - 988
(2007/10/02)
-
- Preparation of 4-substituted pyridines using quaternary pyridine salts
-
A process for preparing a 4-substituted pyridine product from a starting pyridine substituted in the 4-position by a leaving group susceptible to nucleophilic displacement when the starting pyridine is in quaternized form, comprises, quaternizing the starting pyridine under effective acidic conditions with acrylamide, N-monoalkylacrylamide or N-dialkylacrylamide, subjecting the resultant, corresponding quaternized starting pyridine, to a nucleophilic displacement reaction with a reagent which reacts with it to produce the corresponding quaternary salt of the 4-substituted pyridine product, and dequaternizing the latter under effective basic conditions to liberate the 4-substituted pyridine product.
- -
-
-
- Method for making aromatic ethers using diorganoamino pyridinum salt catalyst
-
A method is provided for making aromatic ethers by effecting the displacement of reactive radicals on an activated aromatic nucleus such as a phthalimide with a mono or bisalkali metal phenoxide in the presence of an organic solvent and a dialkylamino branched alkyl substituted pyridinium salt as a phase transfer catalyst. Improved yields of bis(aromatic ethers) are achieved without the production of undesirable by-products, such as alkylated phenols.
- -
-
-
- Amination, III. Trimethylsilanol as Leaving Group, V. Silylation - Amination of Hydroxy N-Heterocycles
-
Hydroxy N-heterocycles such as 18, 21, 26, and others are efficiently aminated in a one-step/one-pot procedure by silylation-amination to give 20, 23 - 25 etc.Silylation converts aromatic hydroxy N-heterocycles into activated and lipophilic intermediates of type 3, 8 which react in situ with ammonia, primary or secondary amines to form the corresponding mono-, bis- or tris-aminated products (5, 10).This addition-elimination of amines to O-silylated heterocycles is Lewis acid-catalysed and proceeds usually in high yields if the leaving group trimethylsilanol is converted in situ by excess silylated agent into hexamethyldisiloxane.Scope and limitations of this simple procedure are discussed.
- Vorbrueggen, Helmut,Krolikiewicz, Konrad
-
p. 1523 - 1541
(2007/10/02)
-
