78073-91-3Relevant academic research and scientific papers
Iodine-catalyzed disproportionation of aryl-substituted ethers under solvent-free reaction conditions
Jereb, Marjan,Vrazic, Dejan
, p. 1978 - 1999 (2013/05/22)
Iodine was demonstrated to be an efficient catalyst for disproportionation of aryl-substituted ethers under solvent-free reaction conditions. Variously substituted 1,1,1′,1′-tetraaryldimethyl ethers were transformed into the corresponding diarylketone and diarylmethane derivatives. I 2-catalyzed transformation of 4-methoxyphenyl substituted ethers yielded mono- and dialkylated Friedel-Crafts products as well. Treatment of trityl alkyl and trityl benzyl ethers with a catalytic amount of iodine produced triphenylmethane and the corresponding aldehydes and ketones. The electron-donating substituents facilitated the reaction, while the electron-withdrawing groups retarded it; the difference in reactivity is not very high. Such an observation may be in favour of hydride transfer, predominantly from the less electron rich side of the ether with more stable carbocation formation. With the isotopic studies it was established that a substantial portion of the C-H bond scission took place in the rate-determining step, while the carbonyl oxygen atom originated from the starting ether, and not from the air. The transformation took place under air and under argon, and HI was not a functioning catalyst.
Kinetics of hydride transfer reactions from hydrosilanes to carbenium ions. Substituent effects in silicenium ions
Mayr, Herbert,Basso, Nib,Hagen, Gisela
, p. 3060 - 3066 (2007/10/02)
Rates of hydride transfer from hydrosilanes HSiR1R2R3 with widely varying substitution to para-substituted diarylcarbenium ions have been measured in dichloromethane solution. Generally the reactions follow a second-order rate law, -d[Ar2CH+]/dt = k2[Ar2CH+][HSiR1R2R3], and k2 is independent of the degree of ion-pairing and the nature of the counterion (exceptions are reported). The reaction rates are almost independent of solvent polarity. Kinetic isotope effects exclude an SET-type mechanism and are in accord with a polar mechanism with rate-determining formation of silicenium ions. The reactivities of para-substituted aryldimethylsilanes are linearly correlated with σp (ρ = -2.46), not with σp+. In the series H3SiHex, H2SiHex2, HSiHex3, the relative reactivities are 1.00:155:7890, and in the corresponding phenyl series the reactivity increase is much smaller (H3SiPh:H2SiPh2:HSiPh3 = 1.00:17.2:119). As a consequence, trihexylsilane is approximately two orders of magnitude more reactive than triphenylsilane though hexylsilane and phenylsilane show similar reactivities. Tris(trimethylsilyl)silane is just slightly more reactive than trimethylsilane. Replacement of hydrogen by chlorine reduces the reactivity by one order of magnitude. Variation of the electrophilicities of the hydride abstractors does not affect the relative reactivities of the silanes, i.e., constant selectivity (Ritchie-type) relationships are encountered. Correlation equations are given, which permit the calculation of hydride transfer rates from hydrosilanes to any carbenium ion on the basis of pkR+ values or the ethanolysis rate constants of the corresponding alkyl chlorides.
Kinetic Hydrogen Isotope Effects in Intermolecular Hydride Transfer from Arylalkanes to 9-Arylfluoren-9-yl Cations
Bethell, Donald,Hare, Gerard J.,Kearney, Paul A.
, p. 684 - 691 (2007/10/02)
Rates of hydride-ion transfer to a series of 9-phenylfluoren-9-yl cations, substituted in the phenyl group, from triphenylmethane and 4,4'-dimethoxydiphenylmethane have been measured at 30 degC in trifluoroacetic acid solution containing 6percent v/v acet
