Jj. Gajewski et al., GENERATION AND CHARACTERIZATION OF ALKYL-SUBSTITUTED M-XYLYLENES IN FLUID SOLUTION AT ROOM-TEMPERATURE, Journal of the American Chemical Society, 116(12), 1994, pp. 5150-5154
Fluoride ion induced generation of isobutylidene from isopropyl trimet
hylsiiyl ketone enol triflate in the presence of 6,6-dimethylfulvene g
ives the [2.2]-m-cyclophane dimer of alpha,alpha,alpha'alpha'-tetramet
hyl-m-xylylene. When isobutylidene is added to 6,6-bis(trideuteriometh
yl)fulvene, the C-13 NMR spectrum of the dimer reveals three quaternar
y carbons in a 1:1:1 ratio, progressively shifted upfield to suggest t
hat two dimers are formed. Saturation of the reactant solutions with d
ioxygen resulted in no dimer formation despite undiminished loss of re
actants. A control experiment indicated that dioxygen does not affect
the formation of the methylenecyclopropane from cyclohexene and isobut
ylidene. Reaction of 6-cyclopropyl-6-methylfulvene with isobutylidene
gave dimers with intact cyclopropane rings. Addition of isobutylidene
to 6-tert-butyl-6-methylfulvene resulted in a non-cyclophane dimer.