32586-14-4Relevant academic research and scientific papers
NMR Spectroscopy of Organolithium Compounds, Part XVI. The Aggregation Behaviour of Butyllithium, Phenyllithium, and Lihtium Diisopropylamide in Dimethoxy- and Diethoxymethane
Bergander, Klaus,He, Runxi,Chandrakumar, Narayanan,Eppers, Oswald,Guenther, Harald
, p. 5861 - 5868 (1994)
Keywords: Organolithium compounds, aggregation behavior, 6Li NMR, 13C NMR.The aggregation behaviour of butyllithium (BuLi), phenyllithium (PhLi), and lithium diisopropylamide (LDA) in dimethoxy- and diethoxymethane (methylal and ethylal, respectively) has been studied by NMR spectroscopy using the isotropic fingerprint method and 13C,6Li as well as 15N,6Li spin-spin coupling constants.In both solvents, LDA exists as a dimer, while BuLi forms a tetramer, PhLi forms a dimer in methylal, whereas two major aggregates exist in ethylal.Due to solvent viscosity at lower temperatures, their structure could not be determined.
Two-State Reactivity in Iron-Catalyzed Alkene Isomerization Confers σ-Base Resistance
Lutz, Sean A.,Hickey, Anne K.,Gao, Yafei,Chen, Chun-Hsing,Smith, Jeremy M.
supporting information, p. 15527 - 15535 (2020/10/20)
A low-coordinate, high spin (S = 3/2) organometallic iron(I) complex is a catalyst for the isomerization of alkenes. A combination of experimental and computational mechanistic studies supports a mechanism in which alkene isomerization occurs by the allyl mechanism. Importantly, while substrate binding occurs on the S = 3/2 surface, oxidative addition to an η1-allyl intermediate only occurs on the S = 1/2 surface. Since this spin state change is only possible when the alkene substrate is bound, the catalyst has high immunity to typical σ-base poisons due to the antibonding interactions of the high spin state.
Regioselective deuteration of alcohols in D2O catalysed by homogeneous manganese and iron pincer complexes
Kar, Sayan,Goeppert, Alain,Sen, Raktim,Kothandaraman, Jotheeswari,Surya Prakash
supporting information, p. 2706 - 2710 (2018/07/05)
We report a convenient and cost-effective protocol for the regioselective deuteration of primary and secondary alcohols using Earth abundant homogeneous first row transition metal pincer catalysts. D2O is utilized as both a deuterium source and a solvent, allowing for a benign inexpensive process. Depending on the metal selected (Mn or Fe), a high degree of deuterium incorporation was observed selectively either at the α and β position (Mn) or exclusively at the α position (Fe), for primary alcohols. This simple, efficient, and cost-effective protocol for alcohol C-H bond deuteration constitutes a powerful tool for the large scale synthesis of deuterated molecules.
Synthesis of sequentially deuterated 1-n-Butyl-3-methylimidazolium ionic liquids
Khrizman, Alexander,Cheng, Hiu Yan,Moyna, Guillermo
experimental part, p. 401 - 407 (2012/07/13)
Deuterium isotopologues of the ionic liquid (IL) 1-n-butyl-3- methylimidazolium chloride ([C4mim]Cl) sequentially labeled on the C-1″, C-1′, C-2′, C-3′, and C-4′ positions of the N-alkyl groups were prepared following a strategy that minimizes
Experimental and theoretical study of tunable 1,3-lithium shift of proparglie/allem lie species, transmetallation and Pd-catalyzed crosscoupling reactions
Zhao, Jinbo,Liu, Yu,He, Qiwen,Li, Yuxue,Ma, Shengming
scheme or table, p. 11361 - 11372 (2010/05/18)
The highly selective tuning of the isomerization from 1-arylalka1,2-dien-l- yllithium to l-arylalka-1,2dien-3-yllithium has been realized in the deprotonation of 1-arylalk-l-yne (conditions A and B) and carbolithiation of l-arylbut-3-en-l-yne with alkyllithium (conditions C and D). Subsequent transmetallation and Pd-catalyzed Negishi coupling reactions afforded 1,1-diaryl or 1,3-diaryl alienes with high selectivity. Deuterium-labeling cross experiments indicated that an intermolecular lithiation process occurred in both 1,3-lithium shift conditions (conditions B and D). 1-Arylalka1,2-diene was confirmed experimentally to be the intermediate. A computational study at the B3LYP level for the isomerization indicated that the acidity of H at the 3-position is higher than that of the H at the 1-position of 1phenyl-l,2-butadiene. Under conditions B, (Pr2NH acts as a proton carrier to finish the 1,3-lithium shift. The overall activation barrier for the rate-determining step in the solvated models is ≈ 21.0 kcal mol-1, indicating that the isomerization is reasonable at room temperature. For the isomerization under conditions D, DFT calculations indicated that the addition of TMEDA (tetramethylethylenediamine) and HMPA (hexamethylphosphoramide) changes the global minimum of the system; among the possible mechanisms (P1-P5) considered, the mechanism catalyzed by dilithiated species (P5) is the most probable one. The overall activation barriers for isomerization in THF and TMEDA solvated models are 22.6 and 19.7 kcal mol-1, respectively, proving that the isomerization may proceed at RT in THF or at -78°C with TMEDA, due to the fact that the solvation of the additives may increase the concentration of 1-phenyl1,2-butadienyllithium monomer by a deaggregation effect.
Cryptoregiochemistry of a Brassica napus fatty acid desaturase (FAD3): A kinetic isotope effect study
Savile,Reed,Meesapyodsuk,Covello,Buist
, p. 1116 - 1121 (2007/10/03)
α-Linolenic acid ((Z,Z,Z)-octadeca-9,12,15-trienoic acid) is biosynthesized by a series of regio- and stereoselective dehydrogenation reactions which are catalyzed by a set of enzymes known as fatty acid desaturases. As part of ongoing research into the mechanism of these remarkable catalysts, we have examined the cryptoregiochemistry (site of initial oxidation) of extraplastidial ω - 3 desaturation as it occurs in the commercially important plant Brassica napus (oilseed rape or canola). The individual deuterium kinetic isotope effects associated with the C-H bond cleavages at C-15 and C-16 of a thiaoleoyl analogue were measured using a convenient in vivo yeast expression system. Competition experiments using appropriately deuterium-labelled 7-thia substrates revealed a large kinetic isotope effect (KIE) (kH/kD = 7.5 ± 0.4) for the C-H bond-breaking step at C-15 while the C-H bond cleavage at C-16 was found to be insensitive to deuterium substitution (kH/kD = 1.0 ± 0.14). These results point to C-15 as the site of initial oxidation in ω - 3 desaturation since the first chemical step in this type of reaction is rupture of a strong, unactivated C-H bond - an energetically difficult process which typically exhibits a large KIE.
Site-selective deuterium labeling of the tetrabutylammonium cation
Heinsen, Melissa J.,Pochapsky, Thomas C.
, p. 473 - 480 (2007/10/03)
Four separate selectively deuterated samples of tetrabutylammonium iodide have been prepared in which each one of the four nonequivalent alkyl carbons is separately and fully deuterated. These samples were prepared for nuclear magnetic resonance (NMR) studies of the aggregation of ion pairs in low polarity solvents.
Intermediacy of ion neutral complexes in the fragmentation of short-chain dialkyl sulfides
Filsak,Budzikiewicz
, p. 601 - 610 (2007/10/03)
The main fragmentation processes after electron ionization of butyl methyl and butyl ethyl sulfides are rationalized by the intermediacy of the ion neutral complex [RSH · methylcyclopropane](+·) as demonstrated by extensive labeling and collision activation studies.
Tritiated chiral alkanes as substrates for soluble methane monooxygenase from Methylococcus capsulatus (Bath): Probes for the mechanism of hydroxylation
Valentine, Ann M.,Wilkinson, Barrie,Liu, Katherine E.,Komar-Panicucci, Sonja,Priestley, Nigel D.,Williams, Philip G.,Morimoto, Hiromi,Floss, Heinz G.,Lippard, Stephen J.
, p. 1818 - 1827 (2007/10/03)
The tritiated chiral alkanes (S)-[1-2H1, 1-3H]ethane, (R)-[1-2H1, 1-3H]ethane, (S)-[1-2H1, 1-3H]butane, (R)[1-2H1, 1-3H]but
Side-chain Effects on the Fragmentation Behaviour of Alkylthiophenes
Lange, D.,Budzikiewicz, H.
, p. 432 - 438 (2007/10/02)
The processes leading to the fragment ions formed from alkylthiophene molecule ions by benzylic cleavage without and with transfer of one hydrogen from the side-chain to the ring and the influence of additional methyl groups on the relative importance of these two fragmentation reactions were investigated.
