767-58-8Relevant articles and documents
MASS SPECTROMETRY FOR INVESTIGATIONS OF GAS-PHASE RADICAL CATION CHEMISTRY. THE TWO STEP CYCLOADDITION OF THE BENZENE RADICAL CATION AND 1,3-BUTADIENE
Holman, R. W.,Rozeboom, M. D.,Gross, M. L.,Warner, C. D.
, p. 6235 - 6244 (1986)
Mass spectrometric techniques are now used extensively for the study of gas-phase radical cation chemistry.The generation and structural properties, the unimolecular and bimolecular chemistry of some representative radical cation systems, and the methods of study are reviewed.The structure of the ionmolecule adduct produced in the reaction of the benzene radical cation and neutral 1,3-butadiene was investigated by collisionally stabilizing the adduct and then acquiring its collision-activated decomposition spectrum.The CAD spectrum of the adduct changes dramatically as a function of the degree of collisional stabilization.This observation is interpreted in terms of two distinct structures for the adduct.The species that is stabilized at 0.7 Torr has a CAD spectrum similar to the 2-phenyl-2-butene radical cation.The second structure, stabilized at 0.1 Torr, has a CAD similar to that of 1-methylindan.The results of these experiments are interpreted in terms of a two-step cycloaddition mechanism for the formation of the 1-methylindan radical cation.
Reductive Cyclization of o-(3-Butenyl)fluorobenzene at Mercury and Lead Cathodes
Loffredo, David M.,Swartz, James E.,Kariv-Miller, Essie
, p. 5953 - 5957 (1989)
The cathodic behavior of o-(3-butenyl)fluorobenzene (1) at mercury and lead cathodes in DMF was investigated.Cyclic voltammograms were recorded, and the products of preparative electrolyses were isolated and identified.The reduction products at either cathode were 1-methylindane (3) and 3-butenylbenzene (2), the first predominating in all experiments with dry solvent.The effects of various reaction conditions on the product composition were studied, and the highest yield of 3 was obtained at a lead cathode at 22 deg C (3/2 = 3.8).Dimethylpyrrolidinium (DMP+) was tested as a possible catalyst for the reduction of 1.It catalyzed the reaction and increased the proportionate amount of the cyclic product.However the mediated process at lead was very inefficient.The mechanism for the reductive cyclization of 1 at mercury and lead and the mediation by DMP+ are discussed.It is proposed that tetraalkylammonium-metals are involved in these processes.
Exploiting the radical reactivity of diazaphosphinanes in hydrodehalogenations and cascade cyclizations
Cheng, Jin-Pei,Yang, Jin-Dong,Zhang, Jingjing
, p. 4786 - 4790 (2020/06/18)
The remarkable reducibility of diazaphosphinanes has been extensively applied in various hydrogenations, based on and yet limited by their well-known hydridic reactivity. Here we exploited their unprecedented radical reactivity to implement hydrodehalogenations and cascade cyclizations originally inaccessible by hydride transfer. These reactions feature a broad substrate scope, high efficiency and simplicity of manipulation. Mechanistic studies suggested a radical chain process in which a phosphinyl radical is generated in a catalytic cycle via hydrogen-atom transfer from diazaphosphinanes. The radical reactivity of diazaphosphinanes disclosed here differs from their well-established hydridic reactivity, and hence, opens a new avenue for diazaphosphinane applications in organic syntheses.
Visible-Light-Induced, Base-Promoted Transition-Metal-Free Dehalogenation of Aryl Fluorides, Chlorides, Bromides, and Iodides
Ding, Ting-Hui,Qu, Jian-Ping,Kang, Yan-Biao
supporting information, p. 3084 - 3088 (2020/04/10)
We report a simple and efficient visible-light-induced transition-metal-free hydrogenation of aryl halides. The combined visible light and base system is used to initiate the desired radical-mediated hydrogenation. A variety of aryl fluorides, chlorides, bromides, and iodides could be reduced to the corresponding (hetero)arenes with excellent yields under mild conditions. Various functional groups and other heterocyclic compounds are tolerated.
Computational Insight into 1,2-Diamine, -Diether, and -Amino Ether Chiral Ligand-Mediated Carbolithiation: A Case of Enantioinduction Reversal
Guyon, Hélène,Castanet, Anne-Sophie,Boussonnière, Anne
, p. 8933 - 8943 (2020/08/28)
trans-1,2-Cyclohexanediamine, -diether, and -amino ether were compared as chiral inducers in the asymmetric intramolecular carbolithiation of olefinic aryllithiums. Switching from diamine to ethereal ligands inverts the sense of asymmetric induction. This reversal of stereoselectivity was investigated through density functional theory calculations. High enantioselectivities observed with diether and amino ether ligands arise from favorable weak interactions between the ligand and the substrate. The relative efficiency of the three ligands and sense of stereoinduction for the most efficient diether and amino ether ligands prove to be foreseeable by modeling the reaction with the parent achiral 1,2-bidentate additives and comparing the diastereomeric transition states stemming from the two half-chair conformations of their lithium chelate.
Competing dehalogenation versus borylation of aryl iodides and bromides under transition-metal-free basic conditions
Niu, Yi-Jie,Sui, Guo-Hui,Zheng, Hong-Xing,Shan, Xiang-Huan,Tie, Lin,Fu, Jia-Le,Qu, Jian-Ping,Kang, Yan-Biao
, p. 10805 - 10813 (2019/09/30)
In this work, selectivity-controllable base-promoted transition-metal-free borylation and dehalogenation of aryl halides are described. Under the conditions of borylation, the dehalogenation which emerges as a competitive side reaction has been well-controlled by carefully controlling the borylation conditions. On the other hand, the dehalogenation using benzaldehyde as a hydrogen source has also been accomplished. The applications of direct radical borylation and dehalogenation of aryl halides demonstrate their synthetic practicability in pharmaceutical-oriented organic synthesis. Based on the experimental evidences, the tBuOK/1,10-Phen-triggered radical nature of both competitive reactions has been revealed.
Ligand-free nickel-catalyzed Kumada couplings of aryl bromides with tert-butyl Grignard reagents
Wu, Zhenghan,Si, Tengda,Xu, Guangqing,Xu, Bin,Tang, Wenjun
supporting information, p. 597 - 600 (2019/01/05)
A ligand-free nickel-catalyzed Kumada cross-coupling of aryl bromides and tert-butyl Grignard reagents led to the formation of a series of tert-butyl aryls in moderate to good yields, excellent tBu/iBu ratios, and good functional group compatibility. A radical coupling process is indicated and a mechanism with a Ni(I)-Ni(III) catalytic cycle is proposed.
Remote, Diastereoselective Cobalt-Catalyzed Alkene Isomerization-Hydroboration: Access to Stereodefined 1,3-Difunctionalized Indanes
Léonard, Nadia G.,Palmer, W. Neil,Friedfeld, Max R.,Bezdek, Máté J.,Chirik, Paul J.
, p. 9034 - 9044 (2019/10/02)
The remote, diastereoselective hydroboration of 2- and 3-substituted indenes with a 2,2′:6′,2″-terpyridine cobalt alkyl precatalyst is described that maintains high regio- and stereoselectivity independent of the starting position of the alkene. Several 1,2- and 1,3-disubstituted indanyl boronate esters were obtained with exclusive (>20:1 dr) selectivity for the trans diastereomer including synthetically versatile, stereodefined diboron derivatives. Alkene isomerization by a putative cobalt hydride intermediate precedes carbon-boron bond formation, leading to the observed regioselectivity for boron incorporation at the unsubstituted C(sp3)-H benzylic site. The regio- and diastereoselectivity of the transformation were maintained independent of the starting position of the alkene, as demonstrated by hydroboration of three isomers of methyl-substituted indene. Deuterium-labeling experiments support rapid and reversible insertion and β-hydride elimination to isomerize 3-methylindene and 1-exo-methylene-indane, accounting for the isotopic distribution observed in the products. Mechanistic studies, including stoichiometric experiments, density functional theory calculations, and kinetic analysis, support a mechanism in which 2,3-alkene insertion into a cobalt hydride intermediate determines both the regio- and diastereoselectivity of the catalytic reaction. Synthetic applications of the indanyl boronate esters were demonstrated through the elaboration of the products to several examples of 1,3-disubstituted indanes, important carbocyclic structural motifs in both pharmacological and bioactive molecules.
Air-Stable α-Diimine Nickel Precatalysts for the Hydrogenation of Hindered, Unactivated Alkenes
Léonard, Nadia G.,Chirik, Paul J.
, p. 342 - 348 (2018/01/17)
Treatment of a mixture of air-stable nickel(II) bis(octanoate), Ni(O2CC7H15)2, and α-diimine ligand, iPrDI or CyADI (iPrDI = [2,6-iPr2-C6H3N=C(CH3)]2, CyADI = [C6H11N=C(CH3)]2) with pinacolborane (HBPin) generated a highly active catalyst for the hydrogenation of hindered, essentially unfunctionalized alkenes. A range of tri- and tetrasubstituted alkenes was hydrogenated and a benchtop procedure for the hydrogenation of 1-phenyl-1-cyclohexene on a multigram scale was demonstrated and represents an advance in catalyst activity and scope for the nickel-catalyzed hydrogenation of this challenging class of alkenes. Deuteration of 1,2-dimethylindene with the in situ-generated nickel catalyst with iPrDI exclusively furnished the 1,2-syn-d2-dimethylindane. With cyclic trisubstituted alkenes, such as 1-methyl-indene and methylcyclohexene, deuteration with the in situ generated nickel catalyst under 4 atm of D2 produced multiple deuterated isotopologues of the alkanes, signaling chain running processes that are competitive with productive hydrogenation. Stoichiometric studies, titration, and deuterium labeling experiments identified that the borane reagent served the dual role of reducing nickel(II) bis(carboxylate) to the previously reported nickel hydride dimer [(iPrDI)NiH]2 and increasing the observed hydrogenation activity. Performing the catalyst activation procedure with D2 gas and HBPin generated both HD and DBPin, establishing that the borane is involved in H2 activation as judged by 1H and 11B nuclear magnetic resonance spectroscopies.
Radical Hydrodehalogenation of Aryl Bromides and Chlorides with Sodium Hydride and 1,4-Dioxane
Hokamp, Tobias,Dewanji, Abhishek,Lübbesmeyer, Maximilian,Mück-Lichtenfeld, Christian,Würthwein, Ernst-Ulrich,Studer, Armido
supporting information, p. 13275 - 13278 (2017/10/09)
A practical method for radical chain reduction of various aryl bromides and chlorides is introduced. The thermal process uses NaH and 1,4-dioxane as reagents and 1,10-phenanthroline as an initiator. Hydrodehalogenation can be combined with typical cyclization reactions, proving the nature of the radical mechanism. These chain reactions proceed by electron catalysis. DFT calculations and mechanistic studies support the suggested mechanism.
