68525-39-3Relevant articles and documents
The Reaction of 2,2,5,5-Tetramethyl-3,4-diphenylhexane with D2. Stereochemical Effects in a High-Temperature Reaction
Guthrie, Robert D.,Sharipov, Rustem V.,Ramakrishnan, Sreekumar,Shi, Buchang,Davis, Burton H.
, p. 4504 - 4509 (2007/10/02)
The thermolysis of 2,2,5,5-tetramethyl-3,4-diphenylhexane was carried out at temperatures above 300 deg C in the absence and presence of D2 (14 MPa).The presence of D2 results in a greatly increased yield of the major product, neopentylbenzene.However, at higher concentrations of starting material, up to 50percent of the neopentylbenzene formed avoids deuterium incorporation, an outcome belived to result partly from participation of the phenylneopentyl radical in radical disproportionation reactions.The meso-isomer of starting material produces a substantial yield of stilbene in both the absence and presence of D2.Under D2, 1,2-diphenylethane is produced, and it is belived that stilbene and other alkenes present serve as D atom traps producing radicals which then participate in termination by disproportionation.Remarkably, the d,l-diastereomer gives a different product distribution than the meso-isomer, giving very little stilbene or other products of tert-butyl group loss.However, both systems produce 1-phenyl-2-methyl-2-propene by methyl radical loss from the phenylneopentyl radical.The formation of such alkenes and the path to termination they provide is blamed for the absence of efficient kinetic chains involving D atoms.
Electrochemical Reduction of (1-bromo-2,2-dimethylpropyl)benzene in Dimethylformamide on Carbon Electrodes
Fry, Albert J.,Powers, Thomas J.
, p. 2498 - 2501 (2007/10/02)
Products from the electrochemical reduction of (1-bromo-2,2-dimethylpropyl)benzene (4a) on carbon electrodes in dimethylformamide containing lithium perchlorate were found to depend upon the electrolysis potential.At relatively positive potentials the products are derived primarily from the coupling of two benzylic radicals, wheres at more negative potentials the products are derived from the corresponding carbanions.This establishes for the first time the mechanism of bibenzyl formation in the electrochemical reduction of benzyl bromides at nonmetallic electrodes.It has also been found that the meso-dl ratios of the 1,2-di-tert-butyl-1,2-diphenylethane products are dependent upon electrolysis potential and that head-to-head coupling of 1-phenyl-2,2-dimethylpropyl radicals is sterically restricted.
Thermolabile Hydrocarbons, XVIII. 1-Substituted Neopentyl radicals and their Dimers
Eichin, Karl-Heinz,Beckhaus, Hans-Dieter,Hellmann, Siegried,Fritz, Hans,Peters, Eva-Maria,et al.
, p. 1787 - 1821 (2007/10/02)
Five 3,4-diaryl-2,2,5,5-tetramethylhexanes 1a - e were prepared as pure meso- and DL-isomers.According to the NMR spectra, x-ray analyses for meso- and DL-1e (with an (FB)2E conformation as energy minimum for DL-1e), and force field calculations the diastereomers have distinctly different minimum energy conformations, rotational potentials, and strain enthalpies.Also the activation parameters for the thermal dissociation into 1-arylneopentyl radicals 2 are typically differing.From an entropy discussion it is concluded that sandwich-like diastereomeric radical complexes are formed in these reactions as first intermediates.Their tightness influences ΔS%.The recombinations of the radicals 2 likewise take place stereoselectively.Their substituent effects on the selectivity can also be understood by primary formation of diastereomeric complexes of radical pairs.
