F:Highly flammable;
498-66-8Relevant articles and documents
Oshima,Tabuchi
, p. 211,212 (1968)
Structure and reactivity of lithium diisopropylamide solvated by polyamines: Evidence of monomer- and dimer-based dehydrohalogenations
Remenar, Julius F.,Collum, David B.
, p. 4081 - 4086 (1998)
6Li and 15N NMR spectroscopic studies show that hexane solutions of LDA containing 1.0 equiv of PMDTA per lithium, monomer is the dominant species. Addition of PMDTA to LDA in toluene affords open dimer at low [PMDTA] and a mixture of LDA monomer and benzyllithium (resulting from toluene deprotonation) at high [PMDTA]. The results are compared and contrasted with previous investigations of LDA solvated by N,N,N',N'-tetramethylethylenediamine (TMEDA) and (±)-trans- N,N,N',N'-tetramethylcyclohexanediamine (TMCDA). The reactivities of LDA solvated by TMEDA, TMCDA, and PMDTA were probed by investigating the dehydrohalogenation of (±)-2-exo-bromonorbornane. All three ligands afford qualitatively similar behavior: (1) a maximum reactivity at low ligand concentrations ascribed to monosolvated LDA dimers and (2) ligand- concentration-independent rates at high ligand concentrations ascribed to monosolvated LDA monomers. Structure and rate differences in hexane and toluene solutions are noted.
Brown,Liu
, p. 2469,2470,2474,2475 (1975)
Homogeneous hydrogenation of norbornadiene with parahydrogen and phosphonic ester phosphine rhodium complexes studied by in situ NMR spectroscopy
Harthun,Woelk,Bargon,Weigt
, p. 11199 - 11206 (1995)
Homogeneous hydrogenation of norbornadiene with enriched parahydrogen (p-H2) and phosphonic ester phosphine rhodium complexes is detected using in situ NMR spectroscopy. The obtained polarization spectra remain unchanged during the catalysis of thf-d8 as a solvent but change with time when the hydrogenation is executed in acetone-d6. The observed phenomenon is attributed to a change of the phase correlation of the transferred parahydrogen nuclei via nuclear singlet-triplet (S/T0) mixing during the reaction. Simultaneously, 31P NMR spectra change indicating a change in the nature of the original rhodium complex when the hydrogenation is carried out in acetone-d6.
Wittig,Klumpp
, p. 607 (1963)
Chelation-based stabilization of the transition structure in a lithium diisopropylamide mediated dehydrobromination: Avoiding the 'universal ground state' assumption
Remenar, Julius F.,Collum, David B.
, p. 5573 - 5582 (1997)
Dehydrobrominations of (±)-2-exo-bromonorbornane (RBr) by lithium diisopropylamide (LDA) were investigated to determine the roles of aggregation and solvation. Elimination with LDA/n-BuOMe occurs by deaggregation of disolvated dimers via a monosolvated monomer transition structure (e.g., [i-Pr2NLi·n-BuOme·-RBr]. In contrast, elimination by LDA- THF displays THF concentration dependencies that are consistent with parallel reaction pathways involving both mono- and disolvated monomer transition structures. Elimination is markedly faster by LDA-DME than by LDA with monodentate ligands and follows a rate law consistent with a transition structure containing a chelated monomeric LDA fragment. A number of hemilabile amino ethers reveal the capacity of different coordinating functionalities to chelate. A protocol based upon kinetic methods affords the relative ligand binding energies in the LDA dimer reactants. Separating contributions of ground state from transition state stabilization allows us to attribute the stabilizing effects of chelation exclusively to the transition structure. The importance of chelating ligands in LDA-mediated dehydrobrominations, but not in previously studied reactions of LDA, sheds light on lithium ion chelation.
Gallazzi et al.
, p. C45 (1971)
Iridium-Catalyzed Asymmetric Hydroalkenylation of Norbornene Derivatives
Sun, Xin,Bai, Xiao-Yan,Li, An-Zhen,Li, Bi-Jie
supporting information, p. 2182 - 2187 (2021/03/01)
Transition-metal-catalyzed asymmetric hydroalkenylation of alkenes provides an atom-economical method to build molecular complexity from easily available materials. Herein we report an iridium-catalyzed asymmetric hydroalkenylation of unconjugated alkenes with acrylamides and acrylates. The catalytic hydroalkenylation of norbornene derivatives occurred to form products with allylic stereocenters with high chemo-, regio-, and stereoselectivities. DFT calculations revealed that the migratory insertion is irreversible and the enantiodetermination step.
Understanding the roles of variable Pd(II)/Pd(0) ratio supported on conjugated poly-azobenzene network: From characteristic alteration in properties to their cooperation towards visible-light-induced selective hydrogenation
Nath, Ipsita,Chakraborty, Jeet,Zhang, Gaoke,Chen, Cheng,Chaemchuen, Somboon,Park, Jihae,Zhuiykov, Serge,Han, Taejun,Verpoort, Francis
, p. 120 - 128 (2020/04/15)
Selective hydrogenation of organic functionalities at environmentally benign conditions using visible light is of great industrial and economic significance. Herein we report visible-light-induced rapid, almost quantitative and selective hydrogenation of olefins to respective mono-reduced products using cooperative performance of Pd(0) nanoparticles (NPs) and Pd(II) ions evenly distributed on a newly synthesized conjugated mesoporous poly-azobenzene network. Role of variable Pd(0)/Pd(II) ratio on the properties of polymeric networks and their overall catalytic abilities is critically investigated. This is the first proposed example of cooperative hydrogenation by simultaneous activation of H2 and unsaturated substrates using Mott-Schottky heterojunction between Pd NPs and the semiconducting polymer, with the help of Pd(II)-site-mediated η-coordination. A control over selective mono-reduction of diene with identical double bonds was also obtained. The catalytic activity retained for other non-olefinic functionalities as well.
