- ESR line shape studies of N (4-n butyl benzilidine) 4-amino 2,2,6,6-tetramethyl piperidine 1-oxide (BBTMPO) in toluene
-
BBTMPO was synthesized by a condensation of 4-n butyl benzaldehyde and 4-amino 2,2,6,6- tetramethyl piperidine N oxide (4-tempamine).The shape of the resulting spin probe, estimated using the Dreiding models, is a spherocone of length 10.7 Angstroem capped by hemispheres of radii 6.6 and 4.0 Angstroem, respectively.The magnetic parameters of BBTMPO in toluene at 77 K were determined.Variable temperature ESR line shape studies in the temperature range of 142-211 K revealed that BBTMPO exhibited anisotropic rotational ditFusion in toluene along the long axis of the spherocone and in the direction parallel to the N-O bond.Rotational diffusion along the long axis was found to be 3+/-0.5 and 7+/-0.5 times faster for frozen and liquid toluene, respectively, than the other two axes.The line shapes have been simulated by using the stochastic Liouville theory of slow-motional effects on ESR spectrum.The slow tumbling spectrum (158 K) in the model-sensitive region showed good agreement for a Brownian model.The plot of τR vs 1/T over the whole temperature range yield a good linear fit with two slopes, with the activation energy for reorientation process of 4.9 kcal/mol in the liquid state, and 9.9 kcal/mol in the solid state.The higher activation energy of rotational reorientation coupled with a lower anisotropy of molecular reorientation (N) in the solid state, indicates that the rotational degrees of freedom is more restricted in the frozen state than in the liquid state.Molecular reorientation for BBTMPO in toluene was analyzed in terms of the hydrodynamic free space model for molecular relaxation in liquids.The stickiness factor S was found to be 0.6 while the anisotropic interaction parameter K which measures the coupling of rotation to translation was found to be 0.7.For perdeuterated 2,2,6,6-tetramethyl-4-piperidine N-oxide (PD-Tempone) in toluene the stickiness factor was calculated to be 0.3, and κ was 0.4.The doubling in size and weight in going from PD-Tempone to BBTMPO increases the stickiness factor and K from 0.3 to 0.6, and 0.4 to 0.7, respectively.The similarity in the structure of BBTMPO to that of liquid crystal methoxy benzilidine butyl aniline (MBBA) and its potential use as a spin probe for MBBA is discussed.
- Hwang, J. S.,Pollet, P.,Saleem, M. M.
-
-
Read Online
- Synthesis of Unbranched 4-Alkylbenzaldehydes
-
The preparation of unbranched 4-alkylbenzaldehydes free of positional and branched-chain isomers by different methods is described.A one-step preparation of the aldehydes is reported which involves the direct hydrogenation of a Friedel-Craft's complex in the presence of Pd/C catalyst.
- Osman, Maged A.
-
-
Read Online
- Scalable Negishi Coupling between Organozinc Compounds and (Hetero)Aryl Bromides under Aerobic Conditions when using Bulk Water or Deep Eutectic Solvents with no Additional Ligands
-
Pd-catalyzed Negishi cross-coupling reactions between organozinc compounds and (hetero)aryl bromides have been reported when using bulk water as the reaction medium in the presence of NaCl or the biodegradable choline chloride/urea eutectic mixture. Both C(sp3)-C(sp2) and C(sp2)-C(sp2) couplings have been found to proceed smoothly, with high chemoselectivity, under mild conditions (room temperature or 60 °C) in air, and in competition with protonolysis. Additional benefits include very short reaction times (20 s), good to excellent yields (up to 98 %), wide substrate scope, and the tolerance of a variety of functional groups. The proposed novel protocol is scalable, and the practicability of the method is further highlighted by an easy recycling of both the catalyst and the eutectic mixture or water.
- Dilauro, Giuseppe,Azzollini, Claudia S.,Vitale, Paola,Salomone, Antonio,Perna, Filippo M.,Capriati, Vito
-
supporting information
p. 10632 - 10636
(2021/04/09)
-
- The Role of LiBr and ZnBr2 on the Cross-Coupling of Aryl Bromides with Bu2Zn or BuZnBr
-
The impact of LiBr and ZnBr2 salts on the Negishi coupling of alkylZnBr and dialkylzinc nucleophiles with both electron-rich and -poor aryl electrophiles has been examined. Focusing only on the more difficult coupling of deactivated (electron-rich) oxidative addition partners, LiBr promotes coupling with BuZnBr, but does not have such an effect with Bu2Zn. The presence of exogenous ZnBr2 shuts down the coupling of both BuZnBr and Bu2Zn, which has been shown before with alkyl electrophiles. Strikingly, the addition of LiBr to Bu2Zn reactions containing exogenous ZnBr2 now fully restores coupling to levels seen without any salt present. This suggests that there is a very important interaction between LiBr and ZnBr2. It is proposed that Lewis acid adducts are forming between ZnBr2 and the electron-rich Pd0 centre and the bromide from LiBr forms inorganic zincates that prevent the catalyst from binding to ZnBr2. This idea has been supported by catalyst design as chlorinating the backbone of the NHC ring of Pd-PEPPSI-IPent to produce Pd-PEPPSI-IPentCl catalyst now gives quantitative conversion, up from a ceiling of only 50 % with the former catalyst.
- Eckert, Philip,Organ, Michael G.
-
supporting information
p. 15751 - 15754
(2019/11/16)
-
- Acceptorless Dehydrogenation of Alcohols Catalyzed by CuI N-Heterocycle Thiolate Complexes
-
CuI N-heterocycle thiolate clusters efficiently catalyze the acceptorless dehydrogenation of alcohols at 70 °C. A variety of secondary/primary benzylic, allylic, and aliphatic alcohols are dehydrogenated to the corresponding ketones and aldehydes in high yields of isolated product upon release of H2. This simple catalytic system is involved in the synthesis of imines through the one-pot reaction of alcohols and amines.
- Tan, Da-Wei,Li, Hong-Xi,Zhang, Meng-Juan,Yao, Jian-Lin,Lang, Jian-Ping
-
p. 1113 - 1118
(2017/03/27)
-
- Metal-catalyzed formal amidation of alkenes under CO-free condition
-
An effective procedure for synthesis of amides from alkenes and [Formula presented] via Pd and Fe catalysts under mild conditions is described. A series of benzamides containing various functional groups can be obtained in reasonable yield and the possible reaction pathway is proposed in this Letter.
- Zhang, Yuanyuan,Ye, Wenjing,Leng, Xue,He, Ying,Zhang, Hui,Xiao, Xiao
-
p. 4203 - 4206
(2016/08/24)
-
- Destruction and Construction: Application of Dearomatization Strategy in Aromatic Carbon-Nitrogen Bond Functionalization
-
The formation of carbon-carbon bonds through the functionalization of aromatic carbon-nitrogen bonds is a highly attractive synthetic strategy in the synthesis of aromatic molecules. In this paper, we report a novel aromatic carbon-nitrogen bond functionalization reaction by using a simple dearomatization strategy. Through this process para-substituted anilines serve as a potential aryl source in the construction of a range of functionalized aromatic molecules, such as quaternary carbon centers, α-keto esters, and aldehydes.
- Wang, Shuo-En,Wang, Linfei,He, Qiuqin,Fan, Renhua
-
p. 13655 - 13658
(2015/11/11)
-
- Reductive carbonylation of aryl halides employing a two-chamber reactor: A protocol for the synthesis of aryl aldehydes including 13C- and D-isotope labeling
-
A protocol has been developed for conducting the palladium-catalyzed reductive carbonylation of aryl iodides and bromides using 9-methylfluorene-9- carbonyl chloride (COgen) as a source of externally delivered carbon monoxide in a sealed two-chamber system (COware), and potassium formate as the in situ hydride source. The method is tolerant to a wide number of functional groups positioned on the aromatic ring, and it can be exploited for the isotope labeling of the aldehyde group. Hence, reductive carbonylations run with 13COgen provide a facile access to 13C-labeled aromatic aldehydes, whereas with DCO2K, the aldehyde is specifically labeled with deuterium. Two examples of double isotopic labeling are also demonstrated. Finally, the method was applied to the specific carbon-13 labeling of the β-amyloid binding compound, florbetaben.
- Korsager, Signe,Taaning, Rolf H.,Lindhardt, Anders T.,Skrydstrup, Troels
-
p. 6112 - 6120
(2013/07/26)
-
- Identification of Trypanosoma brucei leucyl-tRNA synthetase inhibitors by pharmacophore- and docking-based virtual screening and synthesis
-
Human African trypanosomiasis (HAT), caused by the protozoan parasite Trypanosoma brucei, is a neglected fatal disease. Leucyl-tRNA synthetase (LeuRS), which has been successfully applied in the development of antifungal agent, represents a potential antiprotozoal drug target. In this study, a 3D model of T. brucei LeuRS (TbLeuRS) synthetic active site was constructed and subjected to virtual screening using a combination of pharmacophore- and docking-based methods. A new 2-pyrrolinone scaffold was discovered and the structure-activity relationship (SAR) studies aided by the docking model and organic synthesis were carried out. Compounds with various substituents on R1, R2 and R3 were synthesized and their SAR was discussed.
- Zhao, Yaxue,Wang, Qing,Meng, Qingqing,Ding, Dazhong,Yang, Huaiyu,Gao, Guangwei,Li, Dawei,Zhu, Weiliang,Zhou, Huchen
-
experimental part
p. 1240 - 1250
(2012/03/26)
-
- Gold-catalyzed oxidation of arylallenes: Synthesis of quinoxalines and benzimidazoles
-
A gold-catalyzed oxidation of arylallenes to form α-diketones and aldehydes in good yields is presented. Further directed synthesis of quinoxalines and benzimidazoles, via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine, was achieved in high yields.
- Cui, Dong-Mei,Zhuang, Dan-Wen,Chen, Ying,Zhang, Chen
-
experimental part
p. 860 - 865
(2011/08/05)
-
- ACID-SENSITIVE LINKERS FOR DRUG DELIVERY
-
The invention is in general directed to acid-sensitive linkers, and methods of use thereof, such as, for example, in drug delivery methods.
- -
-
Page/Page column 9-11
(2011/04/14)
-
- Cross-coupling reactions through the intramolecular activation of Alkyl(triorgano)silanes
-
(Figure Presented) Cross-Si-ing the Jordan: Cross-coupling reactions of 2-(2-hydroxyprop-2-yl)phenylsubstituted alkylsilanes with a variety of aryl halides proceed in the presence of palladium and copper catalysts. The use of K3PO4 base allows for highly chemoselective alkyl coupling with both primary and secondary alkyl groups (Alk).
- Nakao, Yoshiaki,Takeda, Masahide,Matsumoto, Takuya,Hiyama, Tamejiro
-
supporting information; scheme or table
p. 4447 - 4450
(2010/08/19)
-
- Pd(PPh3)4-PEG 400 catalyzed protocol for the atom-efficient stille cross-coupling reaction of organotin with aryl bromides
-
(Chemical Equation Presented) Aryl bromides (4 equiv) were coupled efficiently with organotin (1 equiv) in an atom-efficient way using the tetra(triphenylphosphine)palladium/polyethylene glycol 400 (Pd(PPh 3)4/PEG 400) catalytic syst
- Zhou, Wen-Jun,Wang, Ke-Hu,Wang, Jin-Xian
-
supporting information; experimental part
p. 5599 - 5602
(2009/12/03)
-
- Tetraphosphine/palladium catalysed Suzuki cross-coupling reactions of aryl halides with alkylboronic acids
-
Through the use of [PdCl(C3H5)]2/cis,cis, cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane as a catalyst, a range of aryl bromides and chlorides undergoes Suzuki cross-coupling with alkylboronic acids in good yields. Several alkyl substituents such as ethyl, n-butyl, n-octyl, isobutyl or 2,2-dimethylpropyl on the alkylboronic acids have been successfully used. The functional group tolerance on the aryl halide is remarkable; substituents such as fluoro, methyl, methoxy, acetyl, formyl, benzoyl, nitro or nitrile are tolerated. Furthermore, this catalyst can be used at low loading, even for reactions of sterically hindered aryl bromides.
- Kondolff, Isabelle,Doucet, Henri,Santelli, Maurice
-
p. 3813 - 3818
(2007/10/03)
-
- Novel synthesis of arylboronic acids by electroreduction of aromatic halides in the presence of trialkyl borates
-
A novel preparation of aryl and heteroarylboronic acids by an electrochemical coupling reaction is described. It is based on the reductive coupling between aromatic or heteroaromatic halides and a trialkyl borate. The reactions are carried out in DMF or THF with the use of sacrificial aluminium or magnesium anodes in a single-compartment cell. Arylboronic acids are obtained with moderate to good selectivities and isolated yields.
- Laza, Carine,Dunach, Elisabet,Serein-Spirau, Francoise,Moreau, Joel J. E.,Vellutini, Luc
-
p. 373 - 375
(2007/10/03)
-
- Manganese-catalyzed substitution of activated aryl halides (X = Cl, Br and F) and aryl ethers by organomagnesium reagents
-
In the presence of manganese chloride (10%), Grignard reagents readily react in THF with aryl bromides, chlorides and even fluorides, as well as aryl methyl ethers bearing in the ortho- or para-position an electron withdrawing activating group (CN, CH=NR, oxazoline). Aryl and N- or S- alkylmagnesium halides have been used successfully. The reaction is performed under mild conditions (0 °C to room temperature, 30 minutes to 24 hours) and leads to cross-coupling products in good yields.
- Cahiez, Gerard,Lepifre, Franck,Ramiandrasoa, Parfait
-
p. 2138 - 2144
(2007/10/03)
-
- Synthesis and characterization of stilbene derivatives for possible incorporation as smart additives in polymers used as packaging films
-
Several series of stilbene derivatives for possible use as smart additives in polymers used as packaging films have been prepared and characterized. Differential scanning calorimetry was performed on some of the stilbenes in order to determine any liquid crystal properties. Those compounds which had multiple phase transitions were also shown to have two liquid crystalline phases according to optical microscopy.
- Day, Gary M.,Howell, Owen T.,Metzler, Michael R.,Woodgate, Paul D.
-
p. 425 - 434
(2007/10/03)
-
- Photochemical behavior of micellized 4-(4′-alkylstyryl)pyridinium salts
-
New photochromic surfactants, l-alkyl-4-(4′-alkylstyryl)lpyridinium halides (CnStzRX; n = 0, 4, 6, 8; R = Me, Et, CH2CH2OH, n-Bu, n-C9H19; X = Br, I), were synthesized and the photochemical behavior of their micellar aggregates in water was characterized in relation to non-micellizing l-methyl-4-stilbazolium ions. Reversible trans-cis isomerization through a photothermal cycle was observed for the micellized CnStzRX. Furthermore, photoreactions upon prolonged irradiation of CnStzRX micelles resulted in a 3-31% formation of thermodynamically least stable syn-head-to-head and ca. 3% of anti- head-to-head dimers. These findings indicate that the self aggregation process of CnStzRX may provide some topologically organized microenvironment affecting the steric and like-charge repulsions of the aggregate components.
- Kozlecki, Tomasz,Wilk, Kazimiera A.
-
p. 645 - 651
(2007/10/03)
-
- Simple and Chemoselective Deprotection of Acetals Using Aqueous Dimethyl Sulfoxide
-
Deprotection of acetals was achieved in aqueous dimethyl sulfoxide under neutral reaction condition.Selective cleavage of acyclic acetals bearing various types of acid labile protecting groups was also reported.
- Kametani, Tetsuji,Kondoh, Hirotsune,Honda, Toshio,Ishizone, Hiroyuki,Suzuki, Yukio,Mori, Wakako
-
p. 901 - 904
(2007/10/02)
-
- Palladium-catalyzed cross-coupling of bromobenzenes, containing an acetyl or a formyl group, with organozinc reagents
-
The reaction of organozinc halides RZnX (R=Bu, Ph; X=Cl, Br) with m- and p-bromoacetophenones in the presence of PdCl2(PPh3)2 in THF/HMPA (THF=tetrahydrofuran; HMPA=N,N,N',N',N'',N''-hexamethylphosphoric triamide) takes place chemoselectively to give the corresponding m- and p-R-substituted acetophenones in high yields.Similarly reaction of RZnX with p-bromobenzaldehyde also proceeds chemoselectively to give the p-R-substituted benzaldehyde in good yields.
- Okamoto, Yuzo,Yoshioka, Katsuaki,Yamana, Tsuyoshi,Mori, Hiroshi
-
p. 285 - 290
(2007/10/02)
-
- New potent antagonists of leukotrienes C4 and D4. 1. Synthesis and structure-activity relationships
-
(p-Amylcinnamoyl)anthranilic acid (3a) had moderate antagonist activities against LTD4-induced smooth muscle contraction on guinea pig ileum and LTC4-induced bronchoconstriction in anesthetized guinea pigs. Modifications were made in the hydrophobic part (cinnamoyl moiety) and the hydrophilic part (anthranilate moiety) of 3a. A series of 8-(benzoylamino)-2-tetrazol-5-yl-1,4-benzodioxans and 8-(benzoylamino)-2-tetrazol-5-yl-4-oxo-4H-1-benzopyrans were revealed to be potent antagonists of leukotrienes C4 and D4. Among both series, ONO-RS-347 (18k) and ONO-RS411 (19h) were the most potent and orally active antagonists, respectively. Structure-activity relationships are discussed.
- Nakai,Konno,Kosuge,Sakuyama,Toda,Arai,Obata,Katsube,Miyamoto,Okegawa,Kawasaki
-
-
- LOW-MELTING NEMATIC 4,4 prime -BIS-(ALKYLBENZAL)-2-CHLORO-1,4-PHENYLENEDIAMINES.
-
A series of 4,4 prime -bis(alkylbenzal)-2-chloro-1,4-phenylenediamines were prepared and their mesomorphic behavior characterized. All homologues showed nematic behavior with broad mesophases and rather low-melting points. The mesomorphic behavior is compared with that obtained from the 4,4 prime -bis-(alkoxybenzal)-1,4-phenylenediamine series and the 4,4 prime -bis-(alkoxybenzal)-2-chloro-1,4-phenylenediamine series.
- Cole,Sowa
-
p. 149 - 153,150, 151
(2007/10/09)
-
