68313-22-4

Upstream product

• 52681-96-6 1,4-dipotassio-1,1,4,4-tetraphenylbutane 
• 530-48-3 1,1-Diphenylethylene 

Downstream Products

• 63469-15-8 1,1,4,4-tetraphenyl-1,4-butanediol 
• 119-61-9 benzophenone 

Relevant academic research and scientific papers

Efficient homogeneous radical-anion chain reactions initiated by dissociative electron transfer to 3,3,6,6-tetraaryl-1,2-dioxanes

A series of 3,3,6,6-tetraaryl1,2-dioxanes (TADs) have been investigated at an inert electrode by using cyclic voltammetry, constant potential electrolysis and digital simulations. The series consists of the phenyl-substituted TAD (la), p-methoxy-aryl TADs (lb, Ic) and the p-methoxy/nitro-bearing TAD (Id). The heterogeneous electron-transfer (ET) reduction is dissociative, causing rupture of the oxygenoxygen bond, which generates a distonic radical-anion that reacts competitively either by β-scission fragmentation or ET Fragmentation of the distonic radical anion yields an alkene, a substituted benzophenone, and a benzophenone radical anion. The benzophenone radical-anion propagates an efficient homogeneous ET-fragmentation chain reaction that accounts for the potential dependence of the product ratios and the low charge consumption observed in the controlled potential electrolysis experiments. Digital simulation of the experimental cyclic voltammograms allowed for estimates of the rate constants of the heterogeneous ET to the 0-0 bond, and for the rate constants for the β-scission fragmentation of the distonic radical-anions. Density functional theory calculations corroborate the differences in the heterogeneous kinetics of the initial dissociative ET The endoperoxides 1a-1c react predominantly by a concerted dissociative ET mechanism, although the data suggests a stepwise dissociative pathway is also competitive. Bearing a nitro-aryl substituent, Id provides a rare example of an endoperoxide that proceeds by a stepwise dissociative ET mechanism. Irrespective of the initial mechanistic details, we find a propagating radicalanion cycle is a general mechanistic feature.

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).

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.

Pyrylium Salts as Photosensitizers in Homogeneous and Heterogeneous Electron-Transfer Catalysis. - A Comparison with Cyano Arenes

Two new triphenylpyrylium salts, both being fixed to a polymeric backbone, have been synthesized.They are sensitizers for photochemically induced electron-transfer reactions, offering the possibility of heterogeneous charge transfer.Their usability in electron-transfer-catalyzed dimerizations and mixed cycloadditions of 1,3-cyclohexadiene and phenyl vinyl ether has been tested in comparison to other common photosensitizers such as 9,10-dicyanoanthracene and 1,4-dicyanonaphthalene.In addition, 2,4,6-triphenylpyrylium tetrafluoroborate was shown to operate as an efficient sensitizer for the dimerization and the photooxygenation of 1,1-diphenylethene.Diverse selectivities in the product formation indicate different mechanisms and are discussed in view of earlier results reported in the literature. - Key Words: Electron-transfer photocatalysis / Electron transfer, photoinduced / Photooxygenation / Pyrylium salts, polymeric / Radical cation cycloadditions

FORMATION OF 1,2-DIOXANES BY ELECTRON-TRANSFER PHOTOOXYGENATION OF 1,1-DISUBSTITUTED ETHYLENES

Electron-rich 1,1-diarylethylenes (1a-e) afford 3,3,6,6-tetraaryl-1,2-dioxanes (3a-e) in high yields (>90percent) when subjected to electrontransfer photooxygenation in the presence of DCA.Whereas 1,1-diphenylethylene (1f) and 1,1-di(p-chlorophenyl)ethylene (1h) yield the 1,2-dioxanes 3f and 3h at 30percent and less than 10percent, respectively, there is negligible (if any) 1,2-dioxane formation with 1,1-di(m-anisyl)ethylene (1i). 1,2-Dioxane formation proceeds in a chain reaction (Scheme 1).N-Vinylcarbazol (1g), however, yields the 1,2-dioxane 3g via the cyclobutane derivative 7 (Scheme 2).