32445-98-0Relevant articles and documents
Photoinduced Electron Transfer in Pinacol Cleavage with Quinones via Highly Labile Cation Radicals. Direct Comparison of Charge-Transfer Excitation and Photosensitization
Perrier, Serge,Sankararaman, Seth,Kochi, Jay K.
, p. 825 - 837 (2007/10/02)
Benzopinacol and related diphenylethane-like donors (D) form electron donor-acceptor (EDA) complexes with chloranil and similar benzoquinones (A), in which the deliberate irradiation of the charge-transfer absorption band (hνCT) leads to oxidative cleavage (retropinacol) via electron transfer.Photosensitization by excitation of the ?-?* band of chloranil and diffusive quenching also effects the C-C bond cleavage of the same donors.The photoefficiencies of both photochemical processes are quantitatively compared with respect to the lifetimes of the pinacol cation radicals (D+ radical), as determined by the competition from back electron transfer and diffusion.These photoinduced processes are considered in the context of electron-transfer for an equivalent thermal reaction which occurs in the dark with high-potential quinones and electron-rich pinacols.
Photochemically Generated Ion and Radical Pairs. Self-Destructive Charge-Transfer Complexes
Maslak, Przemyslaw,Chapman, William H.
, p. 6334 - 6347 (2007/10/02)
Irradiation of CT complexes between 4-methoxy-4'-X-bicumenes, 1a-e (X = H, a; OMe, b; Me, c; CF3, d; CN,) and tetranitromethane (2) results in efficient generation of radical and ion pairs (Φ ca. 0.20).The identity of the final products depends on the dynamics of these pairs, which in turn is dramatically influenced by substitution and solvent.In all cases, 2*- dissociates rapidly ( - (4-) and NO2*.In CH2Cl2, 1a*- reacts with 4- (aromatic trinitromethylation) and undergoes C-C bond fragmentation before diffusional separation of fragments can occur.Thus, a tetrad of reactive intermediates (cumyl radical, NO2*, p-methoxycumyl cation and 4-) are produced in a single solvent cage.The cumyl radical is oxidized by 2, and both cumyl cations undergo α-trinitromethylation.The cumyl cations undergo trinitromethylation in the original solvent cage which is kinetically equivalent to a contact ion pair (CIP).In CH3CN the fragmentation is accompanied by aromatic nitration (radical collapse).In this solvent, the p-methoxycumyl cations produced by cleavage reaction undergo trinitromethylation at the CIP stage, but cumyl cations produced by thermal oxidation of the cumyl radicals are trapped by 4- at the solvent-separated ion pair stage.In CH2Cl2, 1b-c*+ undergo exclusively fragmentation, completely within the solvent cage.The cleavage of 1d-e*+ is much slower, and the radical cations undergo instead aromatic trinitromethylation.The observed substituent effect on the rate of cleavage ( ρ+ = -2.2) indicates significant charge transfer across the scissile bond in the transition state for this process.The products of these reactions are predominantly derived from ion annihilation.The radical coupling processes are limited to radical cation/radical collapse that lead to nitrated products.
Ring-substituted 1,1,2,2-tetraalkylated 1,2-bis(hydroxyphenyl)ethanes. 4. Synthesis, estrogen receptor binding affinity, and evaluation of antiestrogenic and mammary tumor inhibiting activity of symmetrically disubstituted 1,1,2,2-tetramethyl-1,2-bis(hydroxyphenyl)ethanes
Hartmann,Schwarz,Heindl,Schonenberger
, p. 1295 - 1301 (2007/10/02)
The syntheses of symmetrically 2,2'-disubstituted derivatives of 1,1,2,2-tetramethyl-1,2bis(4-hydroxyphenyl)ethane (1) are and of 5,5'-, and 6,6'-disubstituted derivatives of 1,1,2,2-tetramethyl-1,2-bis(3-hydroxyphenyl)ethane (6) are described (1 and 6 are strong antiestrogens with mammary tumor inhibiting activity exhibiting only slight estrogenic properties): (2,2'-substituents) F (2), Cl (3), OCH3 (4), CH3 (5); (5,5'-substituents) Cl (7); (6,6'-substituents) F (8), Cl (9), OCH3 (10), CH3 (11). The synthesis of 1-11 was accomplished by reductive coupling of the corresponding 2-phenyl-2-propanols with TiCl3 and LiAlH4. The binding affinity of the compounds to the calf uterine estrogen receptor was measured relative to that of [3H]estradiol by a competitive binding assay. With the exception of 7 and 10 all other compounds showed relative binding affinity (RBA) values between 0.5 and 6.4% that of estradiol, 2 (RBA value 6.4), and 8 and 9 (4.0 and 3.5), exceeding those of the corresponding unsubstituted 1 and 6 (3.6 and 3.0). Compounds exhibiting RBA values of >2.5% were evaluated in the mouse uterine weight test. The substituted derivatives showed an increase in uterotrophic and a decrease in antiuterotrophic activity compared to 1 and 6. Compound 2 showed a strong, dose-dependent inhibition on the DMBA-induced hormone-dependent mammary tumor of the SD-rat, exceeding that of the parent compound 1. At a dose of 5 mg/kg per day, 2 reduced total tumor area by 47% and caused a complete remission in 74% of the tumors.
