68313-23-5

Upstream product

• 2919-20-2 1,1-di(p-tolyl)ethylene 

Downstream Products

• 68313-24-6 1,1,4,4-Tetra-(4-methyl-phenyl)-butan-1,4-diol 
• 611-97-2 bis(p-methylphenyl)-methanone 

Relevant academic research and scientific papers

Substituent-Dependent Electron-Transfer Induced Photooxygenation of 1,1-Diarylethylenes

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.

Photoreactivities of Contact Charge-Transfer Complexes between 1,1-Diarylethenes and Oxygen Molecules. Dimerization and Oxygenation Accelerated in Medium Polar Solvent

The selective excitation of contact charge-transfer (CCT) bands of 1,1-diarylethenes [Ar = 4-MeOC6H4 (1a); 4-MeC6H4 (1b); Ph (1c)] with molecular oxygen in CH2Cl2 and MeCN resulted in the formation of the corresponding 3,3,6,6-tetraaryl-1,2-dioxanes (2) as a primary product, together with diaryl ketones (3). The reaction mechanism and intermediates for the production of 2 and 3 were studied in terms of the effects of the solvent polarity, additives, substituents on the aromatic rings, and the excitation wavelength on the product distribution, as well as in terms of the result of the photolysis of 2. On the basis of these results, it was shown that 2 was produced through dimer cation radicals of 1, whereas 3 was formed through the photolysis of 2 and the autoxidation of 1 initiated by neutral radical species, which must have been generated by the reaction of monomer cation radicals of 1 (1.+) with a Superoxide anion radical. In particular, the formation of 2 depended to a large degree on the solvent polarity; namely, 2 was produced more efficiently in CH2Cl2 with moderate polarity rather than in MeCN with high polarity. Moreover, the reactivities of monomer and dimer cation radicals of 1 were investigated by γ-radiolyis and pulse radiolysis. For 1a and 1b, the transient-absorption spectra of their dimer cation radicals trapped by oxygen molecules were directly observed at 365 ns after pulse irradiation. The reactivities of 1.+ are also discussed based on the optimum structure, charge density, and spin density, obtained by semi-empirical molecular orbital calculations (PM3 method).

Photooxygenation of 1,1-Diarylethylenes via Addition of Oxygen to the 1,4-Dimer Radical Cations, Catalyzed by 10-Methylacridinium Ion

Photooxygenation of 1,1-diarylethylene occurs efficiently using 10-methylacridinium ion as a photocatalyst to yield the 1,2-dioxane and/or the diaryl ketone depending on the substituents on the aryl groups. The reaction mechanism is revealed based on the dependence of the quantum yields on the concentrations of the alkene and oxygen, the fluorescence quenching of 10-methylacridinium ion by the alkene, and the direct detection of reactive intermediates by applying laser flash spectroscopy as well as pulse radiolysis. The photooxygenation proceeds via photoinduced electron transfer from the alkene to the singlet excited state of 10-methylacridinium ion. The alkene radical cation formed by the photoinduced electron transfer reacts with alkene to give the 1,4-dimer radical cation, which then reacts with oxygen to produce the oxygenated 1,6-radical cation. The subsequent one-electron reduction of the 1,6-radical cation results in formation of the 1,6-biradical which cyclizes to yield 1,2-dioxane derivative or fragmentates to yield diaryl ketone. When the 1,6-biradical is reduced by the alkene itself, the alkene radical cation is regenerated to repeat the radical chain process.

Mechanism of Photochemical Reaction of Contact Charge Transfer Pair between 1,1-Diarylethene and Oxygen

Selective excitation of the contact charge transfer band between 1,1-diarylethene and oxygen in dichloromethane and acetonitrile gave 3,3,6,6-tetraaryl-1,2-dioxane and benzophenone derivative through an electron transfer reaction.The proposed mechanism was confirmed by the direct observation of the dimer cation radical of the olefin trapped by a triplet oxygen in pulse radiolysis.