87923-82-8Relevant articles and documents
Bond Fixation in Annulenes. 16. Synthesis of the 1,2-Dimethyl-3-phenylcyclooctatetraene ->/<- 1,8-Dimethyl-2-phenylcyclooctatetraene Bond Shift Isomer Pair. Probe of the Relative Size of a Flanking Phenyl Substituent by means of Racemization Kinetics
Paquette, Leo A.,Gardlik, John M.,McCullough, Kevin J.,Samodral, Rodney,DeLucca, George,Ouellette, Robert J.
, p. 7649 - 7655 (1983)
Two synthetic approaches to the cyclooctatetrene bond shift isomers 3 ->/octadiene to generate the cyclooctatetraene nucleus.Although 3 dominates over 4 in the equilibrium, it is possible to separate these bond shift isomers by cycloaddition with a triazolinedione.When recourse was made to the endo-bornyl-substituted dienophile, it was ultimately possible to obtain (-)-3 and to determine its rate of racemization.The data indicate that the flanking phenyl group in 3 causes significant rate retardation relative to the trimethyl derivative.This finding contrasts with the behavior of 2 which racemizes more rapidly despite an interstitial phenyl substituent.The source of these dissimilar effects has been clarified by MM2 calculations, the details of which are presented.
