101165-89-3Relevant academic research and scientific papers
The Effect of Phenyl Groups on the Homoconjugation in the Bicycloocta-3,6-dien-2-yl Anion. A 13C NMR Study
Christl, Manfred,Brueckner, Dieter
, p. 2025 - 2049 (2007/10/02)
The effects of deuterium atoms in the positions 2 and 4 of exo-6-bromo- (11) and endo-6-methoxytricyclo2,7>oct-3-ene (12) as well as exo-4-methoxybicycloocta-2,6-diene (13) on their 13C chemical shifts are in line with the previous interpretation of the effects in correspondingly deuterated bicycloocta-3,6-dien-2-yl anions 1, and thus provide evidence for the homoconjugative interaction in 1. 3-Phenylbicycloocta-2,6-diene (16) and endo- (19a) as well as exo-4-phenylbicycloocta-2,6-diene (19b) have been prepared from bicyclooct-6-en-3-one (14) and bicyclohex-2-ene-endo-6-carbaldehyde (17), respectively. 2,4-Diphenylbicycloocta-2,6-diene (6) and 19a,b were deprotonated by methyllithium and n-butyllithium, respectively, whereas the proton abstraction from tricyclo2,7>dodeca-2,4,6,9-tetraene (4) and from 16 required potassium tert-butoxide/n-butyllithium.As products the corresponding bicycloocta-3,6-dien-2-yl anion derivatives have been identified.By means of potassium tert-butoxide/n-butyllithium 19a,b were converted into 21K, i.e. the anion with K+ as counterion.The NMR spectra of 21Li turned out to depend upon the temperature in the range between +45 and -30 deg C in contrast to those of 21K.The 13C NMR spectra of the anions and of the corresponding hydrocarbons are discussed in detail in relation to the spectra of the unsubstituted species 1 and 2.In particular, the wide variations of the chemical shifts of C-6,7 depending upon the substituents of the allylic moiety of the bicycloocta-3,6-dien-2-yl anion system give strong support for the bishomoaromatic nature of these anions.
