The Reaction of 2,2,5,5-Tetramethyl-3,4-diphenylhexane with D2. Stereochemical Effects in a High-Temperature Reaction
作者:Robert D. Guthrie、Rustem V. Sharipov、Sreekumar Ramakrishnan、Buchang Shi、Burtron H. Davis
DOI:10.1021/jo00119a030
日期:1995.7
The thermolysis of 2,2,5,5-tetramethyl-3,4-diphenylhexane was carried out at temperatures above 300 degrees C in the absence and presence of D-2(14 MPa). The presence of D-2 results in a greatly increased yield of the major product, neopentylbenzene. However, at higher concentrations of starting material, up to 50% of the neopentylbenzene formed avoids deuterium incorporation, an outcome believed 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 D-2. Under D-2, 1,2-diphenylethane is produced, and it is believed 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.