107698-23-7Relevant academic research and scientific papers
THE SYNTHESIS OF OCTAVALENE (TRICYCLO2,8>OCTA-3,5-DIENE) AND SEVERAL SUBSTITUTED OCTAVALENES
Christl, Manfred,Lang, Reinhard,Herzog, Clemens
, p. 1585 - 1596 (1986)
The first synthesis of octavalene (1a) is reported.The starting material is homobenzvalene (5), to which monobromocarbene is added.The resulting compound 3a takes up bromine across the central bicyclobutane bond to form the tribromide 7a which undergoes a cyclopropyl bromide-allyl bromide rearrangement on heating.From the product (10a) HBr is eliminated to give 1,3-dibromocyclobutane with a 1,3-butadiene bridge across its 2- and 4-position (11a).Finally, t-butyllithium removes the two Br atoms from 11a and converts it into 4:1 mixture of 1a and cyclooctatetraene.This reaction sequence represents the first application of protective group strategy in bicyclobutane chemistry.Octavalene (1a) is shown to rearrange to cyclotetraene at 50 deg.Deuterium-labeled 1a (1a) is used to prove that a sigmatropic shift does not occur in 1a.Utilizing the above methodology 4-bromooctavalene (1b) and 3-phenyl-5-bromooctavalene (1c) are synthesized from dibromocarbene adducts 3b and c of homobenzvalene (5) and 5-phenylhomobenzvalene (6), respectively.Surprisingly, 1c was accompanied by a small quantity of 3-bromo-1-phenyloctavalene (1d).Possible mechanisms for the addition of bromine to the bicyclobutane system of compounds 3 and for the formation of the octavalenes 1 are discussed.In the (13)C-NMR spectra of 1 and 11 chemical shifts at unexpectedly high field are observed for C-6 of the 1,3-cycloheptadiene moieties.
