- POLY(PHENYLENE) AND M-TERPHENYL AS PROTECTING GROUPS FOR BENZIMIDAZOLIUM HYDROXIDES
-
The present disclosure provides alkaline-stable m-terphenyl benzimidazolium hydroxide compounds, in which the C2-position is attached to a phenyl group having various substituents at the ortho positions. Polymers incorporating m-terphenylene repeating groups derived from these alkaline-stable benzimidazolium hydroxide compounds are also presented, along with their inclusion in ionic membranes and in electrochemical devices.
- -
-
Page/Page column 29; 34; 35
(2017/08/01)
-
- Poly(phenylene) and m-Terphenyl as Powerful Protecting Groups for the Preparation of Stable Organic Hydroxides
-
Four benzimidazolium hydroxide compounds, in which the C2-position is attached to a phenyl group possessing hydrogen, bromine, methyl groups, or phenyl groups at the ortho positions, are prepared and investigated for stability in a quantitative alkaline stability test. The differences between the stability of the various protecting groups in caustic solutions are rationalized on the basis of their crystal structures and DFT calculations. The highest stability was observed for the m-terphenyl-protected benzimidazolium, showing a half-life in 3 m NaOD/CD3OD/D2O at 80 °C of 3240 h. A high-molecular-weight polymer analogue of this model compound is prepared that exhibits excellent mechanical properties, high ionic conductivity and ion-exchange capacity, as well as remarkable hydroxide stability in alkaline solutions: only 5 % degradation after 168 h in 2 m KOH at 80 °C. This is the most stable hydroxide-conducting benzimidazolium polymer to date.
- Wright, Andrew G.,Weissbach, Thomas,Holdcroft, Steven
-
supporting information
p. 4818 - 4821
(2016/04/19)
-
- Synthesis and biological evaluation of analogues of a novel inhibitor of β-amyloid secretion
-
A drug library of 17200 compounds was screened to select small molecules that inhibit the secretion of amyloid β peptide (Aβ), the major component of Alzheimer disease senile plaques, from a human neuronal cell line. Twenty-nine hits were validated that decreased Aβ secretion by >40% at 10 μM, for a 0.17% hit rate. A lead hit was selected for further study based on its activity and low cytotoxicity, and it was found to inhibit Aβ secretion through activation of the α-secretase pathway. Twenty-four commercially available and 53 synthesized analogues were analyzed for activity. Selected analogues were evaluated for biological stability by incubation with hepatoma cells and for transcellular permeability using Caco-2 cell monolayers. The analogue with the best permeability was evaluated in 2-month old amyloid precursor protein transgenic mice and found to acutely reduce cerebral Aβ levels by 40% after a single iv administration.
- Chakrabarti, Enakshi,Ghosh, Subrata,Sadhukhan, Sushabhan,Sayre, Lawrence,Tochtrop, Gregory P.,Smith, Jonathan D.
-
body text
p. 5302 - 5319
(2010/10/20)
-
- Synthesis of pyrrolnitrin and related halogenated phenylpyrroles
-
A general approach to halogenated arylpyrroles, including the antifungal natural product pyrrolnitrin, is described using newly synthesized halogenated pyrroles and 2,6-disubstituted nitrobenzenes or 2,6-disubstituted anilines.
- Morrison, Matthew D.,Hanthorn, Jason J.,Pratt, Derek A.
-
supporting information; experimental part
p. 1051 - 1054
(2009/07/18)
-
- PdII-catalyzed monoselective ortho halogenation of C-H bonds assisted by counter cations: A complementary method to directed ortho lithiation
-
(Chemical Equation Presented) When the counterion counts: The yield and selectivity of the title transformation of benzoic acid derivatives were improved greatly by using tetraalkyl ammonium salts as additives (see scheme; monoselectivity: 5:1-18:1). These effects are attributed to the influence of counter cations. The halogenated products are versatile intermediates for the construction of substituted aromatic compounds. DMF=N,N-dimethylformamide.
- Mei, Tian-Sheng,Giri, Ramesh,Maugel, Nathan,Yu, Jin-Quan
-
supporting information; experimental part
p. 5215 - 5219
(2009/04/11)
-
- Regioselective halogen-metal exchange reaction of 3-substituted 1,2-dibromo arenes: The synthesis of 2-substituted 5-bromobenzoic acids
-
Regioselective halogen-metal exchange reactions using isopropylmagnesium chloride were carried out on 3-substituted 1,2-dibromo arenes. Eleven examples are given. Georg Thieme Verlag Stuttgart.
- Menzel, Karsten,Dimichele, Lisa,Mills, Paul,Frantz, Doug E.,Nelson, Todd D.,Kress, Michael H.
-
p. 1948 - 1952
(2008/02/08)
-
- Halogen-metal exchange of 3-substituted 1,2-dibromoarenes: The use of long-range JCH coupling constants to determine regiochemistry
-
Regioselective halogen/metal exchange reactions were carried out on a series of 3-substituted-1,2-dibromoarenes. Product mixtures were quenched with CO2 to form the corresponding benzoic acid analogs to facilitate HPLC and NMR analysis. Substitution at the 3-position could readily be assigned on the basis of 2D HMBC long-range correlations, while assignment at the 2-position was not as straightforward. The use of three-bond JCH coupling constant measurements, extracted from 1-D 1H coupled 13C experiments, were necessary to render unequivocal regio assignments. Copyright
- DiMichele, Lisa,Menzel, Karsten,Mills, Paul,Frantz, Doug,Nelson, Todd
-
p. 1041 - 1043
(2008/02/05)
-
- Selectivities in reactions of organolithium reagents with unprotected 2-halobenzoic acids
-
(Matrix presented) Exposing 2-fluorobenzoic acid (1a) to 2.2 equiv of LTMP at ca. -78°C leads to deprotonation at the 3-position whereas 2-chloro/bromobenzoic acids (1b,c) are lithiated adjacent to the carboxylate. The resulting dianions 3Li-1a and 6Li-1b
- Gohier, Frederic,Castanet, Anne-Sophie,Mortier, Jacques
-
p. 1919 - 1922
(2007/10/03)
-
- Buttressing Effects Rerouting the Deprotonation and Functionalization of 1,3-Dichloro- and 1,3-Dibromobenzene
-
A systematic comparison between 1,3-difluorobenzene, 1,3-dichlorobenzene, and 1,3-dibromobenzene did not reveal major differences in their behavior towards strong bases such as lithium diisopropylamide or lithium 2,2,6,6-tetramethyl-piperidide. Thus, all 2,6-dihalobenzoic acids 1 are directly accessible by consecutive treatment with a suitable base and dry ice. In contrast, (2,6-dichlorophenyl)- and (2,6-bromo-phenyl)triethylsilane (2a and 2b) were found to undergo deprotonation at the 5-position (affording acids 3 and, after deprotection, 4), whereas the 1,3-difluoro analog is known to react at the 4-position. The 2,4-dihalobenzoic acids 7 were selectively prepared from either the silanes 2 (by bromination at the 4-position, metalation and carboxylation of the neighboring position, followed by desilylation and debromination) or the 1,3-dihalo-2-iodobenzenes 8 (by base-promoted migration of iodine to the 4-position followed by iodine/magnesium permutation and subsequent carboxylation). Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Heiss, Christophe,Marzi, Elena,Schlosser, Manfred
-
p. 4625 - 4629
(2007/10/03)
-
- Extensive halogen scrambling and buttressing effects encountered upon treatment of oligobromoarenes with bases
-
As a rule, tri-, tetra- and pentahaloarenes readily undergo ortho-lithiation when treated with amide-type bases. However, halogen migration occurs whenever the substrate contains three or more contiguous halogen atoms, provided that at least one of them is bromine or iodine. Dismutation and reduction processes often take place concomitantly. In this manner, a variety of organometallic intermediates may be formed, the driving force always being a decrease in basicity. When no such energy gain can be achieved, a sterically crowded substrate may just turn out to be inert; this was found to be the case with 1,5-dibromo-3-fluoro-2-(trimethylsilyl)benzene, 1,5-dibromo-3-fluoro-2,4-bis(trimethylsilyl)benzene, and 1,5-dibromo-3-fluoro-2,4-diiodobenzene. Buttressing effects are apparently strong enough to prevent expedient deprotonation of those substrates.
- Mongin, Florence,Marzi, Elena,Schlosser, Manfred
-
p. 2771 - 2777
(2007/10/03)
-
- Substitution Reactions of Phenylated Aza-Heterocycles. Part 2. Bromination of Some 2,5-Diaryl-1,3,4-oxadiazoles
-
Electrophilic bromination of the title compounds may be achieved using either bromine in oleum, or bromine and potassium bromate in a sulphuric-acetic acid mixture.Under the milder reaction conditions provided by the latter, 2-(p-nitrophenyl)-5-phenyl-1,3,4-oxadiazole (2), the model compound used in this study, is mono- and di-brominated in the phenyl ring.In the first bromination step, all three monobromo-isomers are produced in appreciable amount.The orientation of the second bromination is controlled entirely by the first bromine and not by the oxadiazole substituent: this is confirmed by a separate study of the bromination of the three monobromo-compounds (3a-3c).
- Blackhall, Alexander,Brydon, Donald L.,Javaid, Khalid,Sagar, Anthony J. G.,Smith, David M.
-
p. 3485 - 3497
(2007/10/02)
-