28358-68-1Relevant articles and documents
Toward a Greener Barluenga-Valdés Cross-Coupling: Microwave-Promoted C-C Bond Formation with a Pd/PEG/H2O Recyclable Catalytic System
Lamaa, Diana,Messe, Estelle,Gandon, Vincent,Alami, Mouad,Hamze, Abdallah
supporting information, p. 8708 - 8712 (2019/11/03)
A green Barluenga-Valdés cross-coupling reaction for the synthesis of 1,1-diarylethylenes using palladium catalysis has been developed. The new catalytic system based on Pd/Xphos-SO3Na or Pd/MeDavephos-CF3SO3 in PEG/H2O under microwave irradiation was found to be the best conditions for this transformation. The recyclability of the palladium catalyst system was also studied, and it was found to be active over nine runs without significant loss in its activity.
Oxime-Derived Palladium Complexes as Very Efficient Catalysts for the Heck-Mizoroki Reaction
Alonso, Diego A.,Najera, Carmen,Pacheco, Ma. Carmen
, p. 172 - 183 (2007/10/03)
Oxime-derived, chloro-bridged palladacycles 16 are efficient complexes for the Heck vinylation of aryl halides. The isolated catalysts are thermally stable, not sensitive to air or moisture and easily accessible from inexpensive starting materials. The reaction can be performed under aerobic conditions, with aryl iodides, bromides and chlorides with acrylic esters and olefins displaying turnover numbers (TON) of up to 1010 for phenyl iodide and turnover frequencies (TOF) of 1.4 × 108 h-1. Deactivated aryl bromides undergo the Heck reaction with styrene with TON and TOF values up to 97,000 and 6063 h-1, respectively. Even aryl chlorides undergo the coupling reaction with olefins with TON up to 920. Complexes 16 catalyze the synthesis of 2,3-disubstituted indenones and indoles in good yields via annulation reaction of internal alkynes with o-bromoor o-chlorobenzaldehyde and o-iodoaniline, respectively.
Substituent-Dependent Electron-Transfer Induced Photooxygenation of 1,1-Diarylethylenes
Gollnick, Klaus,Schnatterer, Albert,Utschick, Gerald
, p. 6049 - 6056 (2007/10/02)
Rates and products of 9,10-dicyanoanthracene-sensitized photooxygenations of 1,1-diarylethylenes (1a-r) in acetonitrile were studied.If at least one of the aryl groups carries an electron-donating substituent at the para (or ortho) position (1a-l), 3,3,6,6-tetraaryl-1,2-dioxanes (2a-l) are generated in high yields (85-100percent).Benzophenones (3) are the only other observable products. 1,1-Diphenylethylene (1n) and its m-methoxy (1m), p-chloro (1o,p), and p-nitro (1q,r) derivatives, however, yield mainly benzophenones (3m-r) (>50percent) (the p-nitro compounds only in the presence of biphenyl). 1,2-Dioxanes (2m-p), cyclobutanes (4n-p), and α-tetralones (5m-o) are obtained as side products.Dioxanes, benzophenones, and α-tetralones are products of electron-transfer induced oxygenations involving triplet ground-state molecular oxygen, 3O2.Singlet molecular oxygen, O2(1Δg), contributes to the benzophenone formation from strongly electron-donor substituted diarylethylenes.An exception is the most powerful electron-donor substituted diarylethylene 1a, with which O2(1Δg) undergoes an electron-transfer reaction affording dioxane 2a.Dioxane formation proceeds via free-radical cations 1.+, which enter into a chain reaction with 1, 3O2, and another molecule of 1 to yield dioxane 2 and a new radical cation 1.+ that maintains the chain reaction.The efficiency of this chain process, however, is found to be several orders of magnitude smaller than expected.To explain this result, a 1,6-biradical .1-1-O2. is proposed to be generated in this chain reaction as the product-determining intermediate that predominantly fragments into 3O2 and two molecules of 1.Cyclization to dioxane 2 and transformation to benzophenone 3 occur at presumably less than 0.1percent from this biradical.The pathways leading to cyclobutanes (4) and α-tetralones (5) are also discussed.
