scholarly journals Trialkylammonium Salt Degradation: Implications for Methylation and Cross-coupling

2021 ◽  
Author(s):  
Jack Brandon Washington ◽  
Michele Assante ◽  
Chunhui Yan ◽  
David R McKinney ◽  
Vanessa Juba ◽  
...  
Keyword(s):  
Cross Coupling ◽  
Methyl Groups ◽  
Dual Reactivity ◽  
Aryl Group

Trialkylammonium (most notably N,N,N-trimethylanilinium) salts are known to display dual reactivity through both the aryl group and the N-methyl groups. These salts have thus been widely applied in cross-coupling, aryl...

scholarly journals A Mechanistic Analysis of Trimethylanilinium Salt Degradation: Implications for Methylation and Cross-coupling Applications

2021 ◽  
Author(s):  
Jack B. Washington ◽  
Michele Assante ◽  
Chunhui Yan ◽  
David McKinney ◽  
Vanessa Juba ◽  
...  
Keyword(s):  
Methyl Iodide ◽  
Phase Transfer ◽  
Cross Coupling ◽  
Closed Shell ◽  
Dual Reactivity ◽  
Aryl Group ◽  
H Nmr ◽  
Mechanistic Analysis ◽  
Degradation Analysis ◽  
Physical And Chemical

<i>N,N,N</i>-trimethylanilinium salts are known to display dual reactivity through both the aryl group and the <i>N</i>-methyl groups. These salts have thus been widely applied in cross-coupling, aryl etherification, fluorine radiolabelling, phase-transfer catalysis, supramolecular recognition, polymer design, and (more recently) methylation. However, their application as electrophilic methylating reagents remains somewhat underexplored, and an understanding of their arylation versus methylation reactivities is lacking. This study presents a mechanistic degradation analysis of <i>N,N,N</i>-trimethylanilinium salts and highlights the implications for synthetic applications of this important class of salts. Kinetic degradation studies, in both solid state and solution phases, have delivered insights into the physical and chemical parameters affecting anilinium salt stability. <sup>1</sup>H NMR kinetic analysis of salt degradation has evidenced thermal degradation to methyl iodide and the parent aniline, consistent with a closed-shell S<sub>N</sub>2-centred degradative pathway, and methyl iodide being the key reactive species in applied methylation procedures. Furthermore, the effect of halide and non-nucleophilic counterions on salt degradation has been investigated, along with deuterium isotope and solvent effects. Finally, new mechanistic insights have enabled the investigation of the use of trimethylanilinium salts in O-methylation and in improved cross-coupling strategies.

scholarly journals A Mechanistic Analysis of Trimethylanilinium Salt Degradation: Implications for Methylation and Cross-coupling Applications

2021 ◽  
Author(s):  
Jack B. Washington ◽  
Michele Assante ◽  
Chunhui Yan ◽  
David McKinney ◽  
Vanessa Juba ◽  
...  
Keyword(s):  
Methyl Iodide ◽  
Phase Transfer ◽  
Cross Coupling ◽  
Closed Shell ◽  
Dual Reactivity ◽  
Aryl Group ◽  
H Nmr ◽  
Mechanistic Analysis ◽  
Degradation Analysis ◽  
Physical And Chemical

<i>N,N,N</i>-trimethylanilinium salts are known to display dual reactivity through both the aryl group and the <i>N</i>-methyl groups. These salts have thus been widely applied in cross-coupling, aryl etherification, fluorine radiolabelling, phase-transfer catalysis, supramolecular recognition, polymer design, and (more recently) methylation. However, their application as electrophilic methylating reagents remains somewhat underexplored, and an understanding of their arylation versus methylation reactivities is lacking. This study presents a mechanistic degradation analysis of <i>N,N,N</i>-trimethylanilinium salts and highlights the implications for synthetic applications of this important class of salts. Kinetic degradation studies, in both solid state and solution phases, have delivered insights into the physical and chemical parameters affecting anilinium salt stability. <sup>1</sup>H NMR kinetic analysis of salt degradation has evidenced thermal degradation to methyl iodide and the parent aniline, consistent with a closed-shell S<sub>N</sub>2-centred degradative pathway, and methyl iodide being the key reactive species in applied methylation procedures. Furthermore, the effect of halide and non-nucleophilic counterions on salt degradation has been investigated, along with deuterium isotope and solvent effects. Finally, new mechanistic insights have enabled the investigation of the use of trimethylanilinium salts in O-methylation and in improved cross-coupling strategies.

scholarly journals 1,3-Bis{[(2,6-dimethylphenyl)sulfanyl]methyl}benzene

IUCrData ◽  
2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Bruno Garita-Salazar ◽  
Leslie W. Pineda
Keyword(s):  
Spatial Orientation ◽  
Title Compound ◽  
Steric Effects ◽  
Dihedral Angles ◽  
Methyl Groups ◽  
Pincer Ligand ◽  
Aryl Group ◽  
Compound C ◽  
Methyl Benzene

The structure of the title compound, C24H26S2, an example of a pincer ligand with an SCS-chelation motif, illustrates the steric effects of the methyl groups in the thiophenyl rings at the 2- and 6-positions, forcing a dissimilar spatial orientation of the thiophenyl rings relative to the central aryl group [dihedral angles = 33.58 (7) and 40.49 (7)°]. In the crystal, weak S...S contacts [3.4009 (7) Å] link the molecules into inversion dimers.

Optical limiting properties of D-π-A BODIPY dyes in the presence and absence of methyl groups at the 1,7-positions

2020 ◽  
Vol 24 (09) ◽  
pp. 1129-1137 ◽  
Author(s):  
Aviwe May ◽  
John Mack ◽  
Tebello Nyokong
Keyword(s):  
Dipole Moment ◽  
Optical Limiting ◽  
Second Order ◽  
Methyl Groups ◽  
Free Rotation ◽  
Aryl Group ◽  
Order Of Magnitude ◽  
Meso Position ◽  
Presence And Absence

The optical limiting properties of three meso-pentafluorophenylstyrylBODIPY dyes are investigated in the presence and absence of methyl groups at the 1,7-positions that hinder free rotation of the meso-aryl group. Pentafluorophenyl groups are introduced at the meso-position, while 4-diethylaminostyryl groups are introduced at the 3- and/or 5-positions to form dyes with strong donor-[Formula: see text]-acceptor (D-[Formula: see text]-A) properties to enhance the dipole moment of the molecule. Favorable optical limiting properties are obtained for all three dyes, with the highest second-order hyperpolarizability value obtained for a monostyryl dye with no methyl groups at the 1,7-position. Bromination at the 2,6-positions of a 1,7-methyl substituted dye is found to result in second-order hyperpolarizability that is an order of magnitude lower than that calculated for the analogous non-halogenated dye.

scholarly journals Synthesis of amphiphilic asymmetrical dithienylethenes with aryl groups at the reactive carbons

2019 ◽  
Vol 97 (6) ◽  
pp. 398-405
Author(s):  
M.S. Jemeli Sang ◽  
Jianxin Cai ◽  
Yamuna S. Kandasamy ◽  
R. Scott Murphy
Keyword(s):  
Steric Hindrance ◽  
Substitution Reaction ◽  
Substituent Effect ◽  
Large Change ◽  
Molecular Geometry ◽  
Methyl Groups ◽  
Synthetic Route ◽  
Aryl Substituent ◽  
Aryl Group ◽  
Enhanced Photostability

A synthetic route for the preparation of amphiphilic asymmetrical dithienylethenes that incorporate methyl groups at the 4- and 4′-positions and an aryl group at one of the reactive carbons has been developed. The presence of a bulky aryl substituent ensures a relatively large change in molecular geometry upon photoisomerization, whereas the presence of methyl groups provide enhanced photostability. Notably, a substituent effect was systematically revealed en route to the preparation of the dithienylethene precursors. In particular, this formal substitution reaction was significantly inhibited due to steric hindrance, stemming from the presence of aryl and methyl groups at the alpha positions of the preformed thienyl carbanionic carbon, and an aryl group on the monosubstituted perfluorocyclopentene derivative.

Synthesis and investigation of BODIPYs with restricted meso-8-aryl rotation

2020 ◽  
Vol 24 (05n07) ◽  
pp. 869-877
Author(s):  
Guanyu Zhang ◽  
Maodie Wang ◽  
Caroline Ndung’U ◽  
Petia Bobadova-Parvanova ◽  
Frank R. Fronczek ◽  
...  
Keyword(s):  
Dihedral Angle ◽  
Quantum Yields ◽  
Methyl Groups ◽  
Free Rotation ◽  
Aryl Group ◽  
Chlorine Atoms ◽  
Aryl Ring ◽  
X Ray ◽  
Fluorescence Quantum Yields ◽  
High Fluorescence

Three BODIPYs bearing 1,3,5,7-tetramethyl substituents and a meso-8-aryl group were synthesized and investigated, both experimentally and computationally. The presence of the 1,7-methyl groups and of ortho-substituents on the meso-8-aryl ring prevent free rotation of the meso-8-aryl group, resulting in high fluorescence quantum yields. Substitution at the 2,6-positions of these BODIPYs with chlorine atoms causes pronounced red-shifted absorptions and emissions, and in the case of 2,6-dichloro-1,3,5,7-tetramethyl-8-(2,4,6-triphenylphenyl)-BODIPY 2c increases its fluorescence quantum yields to 0.93 in dichloromethane and 0.98 in toluene. The X-ray structure of 1,3,5,7-tetramethyl-8-(2,4,6-triphenylphenyl)-BODIPY shows increased deviation from planarity and smaller dihedral angle of the meso-8-aryl group compared with the meso-8-phenyl- and meso-8-mesityl-BODIPY analogs. The presence of 2,6-chlorine atoms was found to not significantly affect the rotational barriers of the meso-8-aryl-groups.

Synthesis and functionalization of β-alkyl-meso-triarylcorroles

2015 ◽  
Vol 19 (07) ◽  
pp. 865-873 ◽  
Author(s):  
Giuseppe Pomarico ◽  
Manuela Stefanelli ◽  
Sara Nardis ◽  
Sara Lentini ◽  
Daniel O. Cicero ◽  
...  
Keyword(s):  
Good Yield ◽  
Cross Coupling ◽  
Methyl Groups ◽  
Macrocyclic Ring ◽  
Electronic Distribution ◽  
Synthetic Routes ◽  
Definition Of ◽  
Electron Withdrawing Substituents

After the definition of efficient synthetic routes for the preparation of triarylcorroles, the functionalization of these macrocycles is becoming a necessary and challenging field of research. One important synthetic step is the introduction of substituents able to influence the electronic distribution in the macrocyclic ring. A valuable target would be a corrole macrocycle with some β-pyrrole positions occupied by methyl groups, while exploiting other positions to introduce electron-withdrawing substituents. To explore the scope of this approach, we investigated the bromination and the nitration of the corrole ring and the desired products have been obtained in moderate to good yield. The successful preparation of selectively halogenated corroles is particularly interesting since they are suitable substrates for the preparation of more complex partially alkylated structures using modern cross coupling methodologies.

Selective Preparation of C 2v -Symmetric Hexaphenylbenzene Derivatives through Sequential Suzuki Coupling

Synlett ◽  
2018 ◽  
Vol 29 (12) ◽  
pp. 1597-1600 ◽  
Author(s):  
Tatsuo Kojima ◽  
Shuichi Hiraoka ◽  
Kazuho Ogata
Keyword(s):  
Cross Coupling ◽  
Suzuki Coupling ◽  
Nickel Catalysts ◽  
Phosphine Ligands ◽  
Reaction Conditions ◽  
Aryl Group ◽  
Chloro Group ◽  
Effective Reaction

We have developed effective reaction conditions for the ­Suzuki cross-coupling of chlorinated hexaphenylbenzene derivatives. A chloro group on a hexaphenylbenzene framework exhibits a low reactivity to Suzuki cross-coupling, and only nickel catalysts bearing alkyl-substituted phosphine ligands achieved the coupling. With this as a key step, we succeeded in the selective preparation of a C 2v -symmetric hexaphenylbenzene derivative containing two kinds of aryl group.

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