622408-05-3Relevant academic research and scientific papers
Cobalt-catalyzed cross-coupling reactions of heterocyclic chlorides with arylmagnesium halides and of polyfunctionalized arylcopper reagents with aryl bromides, chlorides, fluorides and tosylates
Korn, Tobias J.,Schade, Matthias A.,Cheemala, Murthy N.,Wirth, Stefan,Guevara, Simon A.,Cahiez, Gerard,Knochel, Paul
, p. 3547 - 3574 (2008/03/14)
A range of aromatic organocopper or organomagnesium compounds undergo smooth cross-coupling reactions with aryl bromides, chlorides, fluorides and tosylates, leading to polyfunctionalized aromatics or heterocycles in the presence of cobalt salts (5-7.5 mol%) as catalysts. Very mild reaction conditions are needed and, in the case of cross-coupling with organocopper compounds, Bu4NI (1 equiv) and 4-fluorostyrene (20 mol%) are essential as promoters for successful couplings. Georg Thieme Verlag Stuttgart.
Cobalt(II)-catalyzed cross-coupling of polyfunctional aryl copper reagents with aryl bromides and chlorides
Korn, Tobias J.,Knochel, Paul
, p. 2947 - 2951 (2007/10/03)
(Chemical Equation Presented) Polyfunctionalized biphenyl and heteroaromatic compounds were formed in the presence of [Co(acac)2], Bu4Nl, and 4-fluorostyrene (3) through a smooth cross-coupling reaction between organocopper reagents 1, prepared by the transmetalation of functionalized aryl magnesium halides with CuCN·2 LiCl, and aryl halides 2 that bear electron-withdrawing substituents. acac = acetylacetonate, DME = 1,2-dimethoxyethane, DMPU = 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.
Photohydration and Photosolvolysis of Biphenyl Alkenes and Alcohols via Biphenyl Quinone Methide-type Intermediates and Diarylmethyl Carbocations
Brousmiche, Darryl W.,Xu, Musheng,Lukeman, Matthew,Wan, Peter
, p. 12961 - 12970 (2007/10/03)
Evidence is presented for the photochemical generation of novel biphenyl quinone methide (BQM)-type intermediates on photolysis of hydroxybiphenyl alkenes 7 and 8 and hydroxybiphenyl alcohols 9 and 10. Mechanistic investigations utilizing product, fluorescence, and nanosecond laser flash photolysis (LFP) studies indicate two distinct pathways for the formation of these BQMs depending upon the functional groups of the progenitor. Formal excited-state intramolecular proton transfer (ESIPT) between the phenol and the alkene led to BQMs upon irradiation of the hydroxybiphenyl alkenes 7 and 8, while excited-state proton transfer (ESPT) to solvent followed by dehydroxylation was responsible for BQM formation from the hydroxybiphenyl alcohols 9 and 10. Photolysis of 7 and 8 in aqueous CH3CN gave photohydration products via attack of water on the respective BQMs, while photolysis of the analogous methyl ethers (of the phenolic moiety) gave only carbocation intermediates. Hydroxybiphenyl alcohols 9 and 10 yielded the corresponding photomethanolysis products in aqueous methanol, through attack of CH3OH on the respective BQMs. Although no evidence was found for BQM formation in LFP studies of 8 and 10, due to its suspected short lifetime, the respective diaryl carbocation (λmax 420 nm, τ = 8.5 μs) has been observed upon irradiation of 8 in 2,2,2-trifluoroethanol. A BQM (λmax 580 nm) was observed for 9 but not for 10, the latter having more complex chemistry on laser excitation, resulting in a transient that appears to mask any BQM absorption. Significant quenching of fluorescence from the hydroxybiphenyl alkenes at low water content implies that H 2O is directly involved in reaction from the singlet excited state. The decrease in fluorescence intensity of 8 was found to depend on [H 2O]3; however, the distance required for ESIPT in these systems is too large to be bridged by a water trimer. The nonlinear quenching has been attributed to deprotonation of the phenol by two water molecules, with concerted protonation at the alkene by another molecule of water. Fluorescence quenching of the hydroxybiphenyl alcohols required much higher water content, implying a different mechanism of reaction, consistent with the proposal of ESPT (to solvent water) followed by dehydroxylation.
