The Reaction of 2,2,5,5-Tetramethyl-3,4-diphenylhexane with D2. Stereochemical Effects in a High-Temperature Reaction

Article abstract of DOI:10.1021/jo00119a030

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.