Bridgehead free radical stability. The decomposition of t-butylperoxyesters of the 1-adamantyl, 1-bicyclo[2•2•2]octyl, and 1-norbornyl systems

Abstract

The I-butylperoxyesters of 1-adamantyl, 1-bicyclo[2-2.2]octyl, and 1-norbornyl carboxylic acids thermally undergo first order, free radical decomposition in cumene with relative rate constants at 80' of 1 .O, 0.07, and 0.001 respectively. As measures of the stability of the derived bridgehead free radicals, the rates span a range much narrower than that for carbonium ion formation at these strained positions. The results are consistent with suggestions that free radicals have smaller force constants for out-of-plane bending than do the corresponding carbonium ions.

Chemistry of bivalent carbon intermediates. VI. Photolysis of 2-butylphenyldiazomethane

“…Attempts were made to substantiate the "multiplicity equilibration" hypothesis by studying the temperature dependence of the addition of the carbene from 1 {i.e. 9 and/or 10) to czj-2-butene and by studying the effect of oxygen on the reaction. No temperature dependence of the stereoselectivity down to -72°was noted.…”

Decomposition and isomerization of bridgehead cis 1,2-diazenes (azoalkanes)

“…1978, 111, 596. (62) Timberlake, J. W., unpublished results. (63) Some product data for perester thermolysis in cumene can be found in ref 27 rrazu-BisC 1 -adamantyl)diazene was obtained in 80% yield after chromatography (silica gel) and sublimation [120 °C (0.1 mm)]: mp 280-285 °C (lit.65 mp 280-284 °C).…”

Synthesis of azabicyclic systems using nitrogen-directed radical rearrangements

“…These species are sterically similar, but differ in their electronic nature because the 1-adamantyl group is unable to participate in hyperconjugative radical stabilisation. 45,46 From these latter observations it may be inferred that the origin of the selectivity is mainly due to the steric demand of the adding radical alkyl group.…”