591-26-4Relevant academic research and scientific papers
Mechanistic Insight into H/D Exchange by a Pentanuclear Ni-H Cluster and Synthesis and Characterization of Structural Analogues of Potential Intermediates
Shoshani, Manar M.,Liu, Junyang,Johnson, Samuel A.
supporting information, p. 116 - 126 (2018/01/17)
Experiments to gain mechanistic insight into catalytic H/D exchange of unactivated arenes by [(iPr3P)Ni]5H6 (1) are described. The reaction order with respect to 1, arene substrate, and added iPr3P were determined, as well as the temperature dependence of reaction rate. Site-selectivity data were obtained by monitoring the reaction of 1 with fluorobenzene and 2-methoxynaphthalene. H/D exchange competition reactions between arenes reacted with 1 were performed. The addition of an excess of Hg to a solution of 1 provided the new heterometallic cluster [(iPr3P)Ni]5H6(μ4-Hg) (2); this species also undergoes H/D exchange with C6D6, albeit more slowly than 1. Reaction of cluster 1 with TlCp (Cp = C5H5) gave (η5-Cp)Ni[(iPr3P)Ni]4(μ2-H)4(μ4-Tl) (3) with the loss of H2. A similar transfer of cyclopentadienyl to Ni occurred when 1 was reacted with MgCp2, to give (η5-Cp)Ni[(iPr3P)Ni]4H6(μ4-MgCp) (4), but not H2 loss. Reaction of 1 with cyclopentadiene gave the 5-coordinate hydride complex (η5-Cp)Ni[(iPr3P)Ni]4(μ2-H)4(μ5-H) (5). The Cp? analogue, (η5-Cp)Ni[(iPr3P)Ni]4(μ2-H)4(μ5-H) (6) (where Cp? = C5Me5), was synthesized by reacting 1 with LiCp? in THF, or by reaction of 1 with pentamethylcyclopentadiene.
Metal-Free sp2-C-H Borylation as a Common Reactivity Pattern of Frustrated 2-Aminophenylboranes
Chernichenko, Konstantin,Lindqvist, Markus,Kótai, Bianka,Nieger, Martin,Sorochkina, Kristina,Pápai, Imre,Repo, Timo
supporting information, p. 4860 - 4868 (2016/05/10)
C-H borylation is a powerful and atom-efficient method for converting affordable and abundant chemicals into versatile organic reagents used in the production of fine chemicals and functional materials. Herein we report a facile C-H borylation of aromatic and olefinic C-H bonds with 2-aminophenylboranes. Computational and experimental studies reveal that the metal-free C-H insertion proceeds via a frustrated Lewis pair mechanism involving heterolytic splitting of the C-H bond by cooperative action of the amine and boryl groups. The adapted geometry of the reactive B and N centers results in an unprecedentently low kinetic barrier for both insertion into the sp2-C-H bond and intramolecular protonation of the sp2-C-B bond in 2-ammoniophenyl(aryl)- or -(alkenyl)borates. This common reactivity pattern serves as a platform for various catalytic reactions such as C-H borylation and hydrogenation of alkynes. In particular, we demonstrate that simple 2-aminopyridinium salts efficiently catalyze the C-H borylation of hetarenes with catecholborane. This reaction is presumably mediated by a borenium species isoelectronic to 2-aminophenylboranes.
A product analytical study of the thermal and photolytic decomposition of some arenediazonium salts in solution
Canning, Peter S. J.,Maskill, Howard,McCrudden, Katharine,Sexton, Brian
, p. 789 - 800 (2007/10/03)
Products of thermal and photochemical reactions of eleven arenediazonium tetrafluoroborates in various solvents have been analyzed. All compounds in most solvents undergo unimolecular heterolysis to give singlet aryl cations which are captured by solvent. This mechanism is dominant for arenediazonium ions without electron-withdrawing substituents in all solvents, and the only reaction observed in water. Additionally, appreciable yields of fluoroarenes are obtained by fluoride abstraction by the aryl cation from fluorinated solvents and from tetrafluoroborate in fluorinated solvents. Yields from photochemical processes are very similar to those from thermal reactions indicating that the main reactions proceed through common or very similar intermediates. Aryl cations formed from ion-paired diazonium ions may react with the counterion, but fragmentation of dissociated diazonium ions leads only to solvent-derived product. Some arenediazonium ions in some solvents undergo an alternative radical reaction leading principally to hydrodediazoniation. It is proposed that this reaction involves initial rate-limiting electron transfer from ethanol to the arenediazonium ion followed rapidly by homolysis of the resultant aryldiazenyl radical. Within the same solvent cage, the aryl radical then either abstracts an α-hydrogen from the ethanol radical cation generated in the first step to give the reduction product and protonated acetaldehyde, or combines with it at the oxygen to give a protonated aryl ethyl ether.
The thermal conversions of 6,6-difluorobicyclo[3.1.0]hex-2-enes to fluorobenzenes. An interesting dichotomy of mechanisms
Dolbier Jr.,Keaffaber,Burkholder,Koroniak,Pradhan
, p. 9649 - 9660 (2007/10/02)
A kinetic study of the thermal, dehydrofluorinative aromatization reactions of two ostensibly-similar 6,6-difluorobicyclo[3.1.0]hex-2-ene systems led to the conclusion that drastically different mechanisms operate for the two reactions. Activation parameters, solvent effects, kinetic isotope effects, isotope labelling experiments and observation of reactive intermediates all contributed to the conclusion that the reaction of 6,6-difluorobicyclo[3.1.0]hex-2-ene, 1, proceeds via a homolytic hydrogen-shift rearrangement, while the reaction of 2,3-benzo-6,6-difluorobicyclo[3.1.0]hex-2-ene, 6, proceeds via a solvolytic mechanism involving rate-determining carbocation formation.
