Photohomolysis and Photoionization of Substituted Tetraphenylethanes and C-C Fragmentation of 1,1,2,2-Tetra(p-R-phenyl)ethane Radical Cations (R=H, CH3, OCH3, Cl)
摘要:
On photolysis of a series of tetraphenylethanes in 2,2,2-trifluoroethanol (TFE) solution with 248 nm light, homolysis of the central C-C bond occurs to yield the corresponding substituted diphenylmethyl radicals, in a process requiring one quantum of light. A second process takes place under conditions of high photon fluxes, namely biphotonic photoionization to produce a radical cation, which subsequently undergoes efficient C-C scission of the aliphatic central bond to yield the radical and carbocation fragments. Photoionization and photohomolysis are the preferred processes of excited state deactivation in the solvents acetonitrile, TFE, and 1,1,1,3,3,3-hexafluoroisopropanol. The lifetime of the radical cation could be directly determined by following the formation rates of the fragments in solution. The cations were characterized by their UV absorption spectra and electrophilic reactivities.
blocks that are widely used in organic synthesis, and they are typically prepared by the homocoupling of halides, organometallics, and ethers. Herein, we report an approach to this class of compounds using alcohols, which are more stable and readily available. The reaction proceeds via nickel-catalyzed and dimethyl oxalate assisted dynamic kinetic homocoupling of benzyl alcohols. Both primary and secondary
Generation and Reactivity Studies of Diarylmethyl Radical Pairs in Crystalline Tetraarylacetones via Laser Flash Photolysis Using Nanocrystalline Suspensions
作者:Jin H. Park、Melissa Hughs、Tim S. Chung、A. Jean-Luc Ayitou、Vanessa M. Breslin、Miguel A. Garcia-Garibay
DOI:10.1021/jacs.7b04449
日期:2017.9.27
The nanosecond electronic spectra and kinetics of the radical pairs from various crystalline tetraarylacetones were obtained using transmission laser flashphotolysis methods by taking advantage of aqueous nanocrystalline suspensions in the presence of submicellar CTAB, which acts as a surface passivator. After showing that all tetraarylacetones react efficiently by a photodecarbonylation reaction
Diaryl thioketones are selectively reduced with ytterbium metal to diarylmethanethiols, diarylmethanes or tetraarylethylenes, via thiometallacycle intermediates which undergo electrophilic coupling at thiocarbonyl carbon and sulfur.
Palladium-Catalyzed Reaction of 2-Hydroxy-2-methylpropiophenone with Aryl Bromides: A Unique Multiple Arylation via Successive C−C and C−H Bond Cleavages
2-Hydroxy-2-methylpropiophenone undergoes a unique multiple arylation via C-C and C-H bondcleavages upon treatment with excess aryl bromides in the presence of a palladium catalyst to give 1,1,2,2-tetraarylethanes and 4,4-diaryl-1-phenylisochroman-3-ones.
2-Hydroxy-2-methylpropiophenone 在钯催化剂存在下用过量的芳基溴化物处理后,通过 CC 和 CH 键裂解发生独特的多重芳基化,得到 1,1,2,2-四芳基乙烷和 4,4-二芳基-1 -phenylisochroman-3-ones。
Restricted rotation about the aliphatic carbon–carbon bond in 1,2-disubstituted tetra-arylethanes
作者:P. J. M. Burchill、N. Thorne
DOI:10.1039/j39680000696
日期:——
The existence of stable rotational isomers of 1,2-dichlorotetraphenylethane previously reported, is shown to be incorrect, since dipole moment measurements indicate the presence of the trans-form only. Infrared studies of a number of 1,2-disubstituted tetra-arylethanes fail to account for the existence of possible gauche-forms, except in the case of the ethane-1,2-diols which occur exclusively in this