115352-07-3Relevant academic research and scientific papers
Direct measurement of ultrafast carbon-carbon cleavage rates via the subpicosecond charge-transfer activation of pinacols
Bockman,Hubig,Kochi
, p. 6542 - 6547 (2007/10/03)
Highly transient (benzpinacol) cation radicals (D2+.) and their ultrafast mesolytic fragmentations to the diarylhydroxymethyl radical (D.) and cation (D+) are directly observed on the early picosecond time scale upon the charge-transfer photoactivation of the intermolecular donor-acceptor complexes of pinacol donors with methyl viologen. Ultrashort lifetimes of the cation radicals with τ ~ 10 ps obtain (for the first time) from quantitative kinetics analysis of the time-resolved spectroscopic results. These rapid C-C bond scissions successfully compete with back-electron transfer, which normally predominates on this time scale, and lead to exceptionally high efficiencies for the oxidative fragmentation of pinacols.
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.
Reductive Coupling of Carbonyl Compounds with Zinc and Trimethylchlorosilane To Produce O-Silylated Pinacols. Effect of Ultrasonic Waves
So, Jeung-Ho,Park, Moon-Kyeu,Boudjouk, Philip
, p. 5871 - 5875 (2007/10/02)
Trimethylchlorosilane reacts with carbonyl compounds in the presence of zinc to give O-silylated pinacols, vicinal bis(trimethylsiloxy)alkanes, in good yields via reductive dimerization.This is very mild route to bis(siloxy)alkanes, which are easily converted to pinacols or pinacolones in excellent yields.Electron-donating groups accelerate coupling while electron-withdrawing groups have an inhibiting effect.Cross-coupling reactions yield a mixture of bis(siloxy)alkanes.Ultrasonic irradiations of these reactions increases the yields up to 50percent compared to stirring at the same temperature.
