6338-19-8Relevant academic research and scientific papers
Electrocatalytic Reduction of C-C π-Bonds via a Cobaltocene-Derived Concerted Proton-Electron Transfer Mediator: Fumarate Hydrogenation as a Model Study
Derosa, Joseph,Garrido-Barros, Pablo,Peters, Jonas C.
supporting information, p. 9303 - 9307 (2021/07/19)
Reductive concerted proton-electron transfer (CPET) is poorly developed for the reduction of C-C π-bonds, including for activated alkenes that can succumb to deleterious pathways (e.g., a competing hydrogen evolution reaction or oligomerization) in a standard electrochemical reduction. We demonstrate herein that selective hydrogenation of the C-C π-bond of fumarate esters can be achieved via electrocatalytic CPET (eCPET) using a CPET mediator comprising cobaltocene with a tethered Br?nsted base. High selectivity for electrocatalytic hydrogenation is observed only when the mediator is present. Mechanistic analysis sheds light on two distinct kinetic regimes based on the substrate concentration: low fumarate concentrations operate via rate-limiting CPET followed by an electron-transfer/proton-transfer (ET/PT) step, whereas high concentrations operate via CPET followed by a rate-limiting ET/PT step.
Electro-organic reactions. Part 54: Quinodimethane chemistry; Part 2 - Electrogeneration and reactivity of o-quinodimethanes
Utley, James H.P.,Ramesh, Shalini,Salvatella, Xavier,Szunerits, Sabine,Motevalli, Majid,Nielsen, Merete F.
, p. 153 - 163 (2007/10/03)
The electrochemical generation and characterisation of a variety of o-quinodimethanes (o-QDMs) are described together with the outcome of preparative experiments in which they are key intermediates. The quinodimethanes are conveniently formed, in DMF, by both direct and redox-catalysed electroreduction of 1,2-bis(halomethyl)arenes. Their predominant reaction is polymerisation to poly(o-xylylene) (o-PX) polymers. In the presence of dienophiles the electrogenerated o-QDMs may undergo efficient cycloaddition reaction and distinctions between the possible mechanisms have been attempted on the basis of voltammetric, preparative and stereochemical experiments. Contrary to the precedent of the corresponding methyl ester, diphenyl maleate radical-anion isomerises only slowly to the fumarate radical-anion, yet co-electrolysis of 2,3-bis(bromomethyl)-1,4-dimethoxybenzene and diphenyl maleate or diphenyl fumarate gives exclusively the corresponding trans-adduct. Co-electrolysis of dimethyl maleate with either 1,2-bis(bromomethyl)benzene (more easily reduced) or 2,3-bis(bromomethyl)-1,4-dimethoxybenzene (less easily reduced) gave only o-PX polymer. The results are rationalised in terms of a double nucleophilic substitution mechanism where electron transfer between dienophile radical-anion and dihalide is relatively slow. Where electron transfer from maleate or fumarate radical-anions is likely to be fast o-quinodimethanes are formed by redox-catalysis and they polymerise rather than undergo Diels-Alder reaction. Dimerisation of the dienophile radical-anions, with k2 = 104 to 105 M-1 s-1, does not apparently compete with nucleophilic substitution or, where relevant, electron transfer.
Generation and Reactions of Novel Copper Carbenoids through a Stoichiometric Reaction of Copper Metal with gem-Dichlorides in Dimethyl Sulfoxide
Tezuka, Yasuyuki,Hashimoto, Akio,Ushizaka, Koh,Imai, Kiyokazu
, p. 329 - 333 (2007/10/02)
Copper metal and such gem-dichlorides as α,α-dichloro acid esters, 1a-e, diphenyldichloromethane, 2, benzal chloride, 3, 1,1-dichloro-2-butene, 5, and carbon tetrachloride, 6, were found to produce copper carbenoid intermediates via α,α-elimination of dichlorides along with the formation of CuCl2(DMSO)2.Thus, 1 and 2 gave substituted olefins via a carbenoid coupling reaction.From 5 and 6, reaction products via the oxygen abstraction from DMSO were produced together with dimethyl sulfide; 3 and 4 were found to cause both types of reactions.The carbenoid intermediates formed from 1 did not cause cyclopropanation reaction with cyclohexene in contrast to the conventional carbalkoxy carbenoid generated by a decomposition reaction of ethyl diazoacetate.Also the carbenoid coupling reaction was completely inhibited by the addition of triphenylphosphine, which was contrastive to the formation of phosphonium ylide with a carbenoid from ethyl diazoacetate.
CHEMICAL AND PHYSICAL PROPERTIES OF FLUORENYLIDENE: EQUILIBRATION OF THE SINGLET AND TRIPLET CARBENES.
Grasse,Brauer,Zupancic,Kaufmann,Schuster
, p. 6833 - 6845 (2007/10/02)
Irradiation of 9-diazofluorene, with a pulsed laser on a picosecond or nanosecond time scale at room temperature, or at 10 K in a glassy matrix, gives detectable fluorenylidene. This species is shown to exist, under most experimental conditions, as a rapi
