@Article{publ_mods_00000056,
  author = 	{Ferri, Fabiola
		and Br{\"u}ckner, Reinhard
		and Herges, Rainer},
  title = 	{Straightforward syntheses of biradical-producing bicyclic dienediynes---dienediyne ketones cycloaromatize ia the Saito--Myers and not ia the neocarzinostatin pathway},
  journal = 	{New Journal of Chemistry},
  year = 	{1998},
  publisher = 	{Royal Society of Chemistry},
  address = 	{London},
  volume = 	{22},
  number = 	{5},
  pages = 	{531--545},
  keywords = 	{Neocarzinostatin},
  abstract = 	{The dienediyne models 23 and 28 of the pharmacophore of the antitumor natural product neocarzinostatin were
prepared. Each synthesis requires only six steps from a-formylcyclohexanone. Our approach uses two key steps.
The Ðrst consists of one-pot biscoupling reactions between propargyl alcohol, 2,2-dimethyl-3-butyn-1-ol and the
bis(enoltri{\~{N}}uoromethanesulfonate) 17. The second key step corresponds to ring-closing pinacol coupling
reactions of the dialdehydes 20 and 25. The dienediyne models 23 and 28 cycloaromatized efficiently when
treated with methyl thioglycolate and 1,4-cyclohexadiene at 25 {\textexclamdown}C via a Saito{\`E}Myers cyclization4 (to give the
octahydroanthracenones 29, iso-29 and octahydrophenanthrenones 34, 35, respectively); in addition, we isolated
compounds tentatively assigned as the octahydrobenzazulenones 30 and iso-30, which would stem from a
competing Schmittel cyclization. According to density functional theory (B3LYP/6-31G*) and ab initio
calculations [CASMP2(2.2)/6-31G//CAS(2.2)/6-31G], the core structures of the octahydroanthracenones and
octahydrophenanthrenones obtained here and elsewhere form via the Saito{\`E}Myers cyclization of enyneallenyl
ketones 53 to toluene-a,meta biradicals 55 and not via neocarzinostatin-like cycloaromatizations of the
tautomeric enyne[3]cumulenols 54 to styrene a,meta-biradicals 56. This is so because, on the one hand, the two
cyclization modes are predicted to have similar activation barriers (Saito{\`E}Myers: 16.0 kcal mol{\~}1;
neocarzinostatin type: 18.3 kcal mol{\~}1) but, on the other hand, the enyneallenyl ketone 53 is a much more
stable (21.1 kcal mol{\~}1) cycloaromatization substrate than the enynecumulenol 54. In addition, the Saito{\`E}Myers
cyclization product 55 is calculated to be considerably more stable (35.3 kcal mol{\~}1) than the
neocarzinostatin-type cycloaromatization product 56.},
  note = 	{http://xlink.rsc.org/?DOI=a709205i},
  issn = 	{1144-0546},
  doi = 	{10.1039/a709205i},
  url = 	{https://macau.uni-kiel.de/receive/publ_mods_00000056},
  url = 	{https://doi.org/10.1039/a709205i},
  file = 	{:https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/macau_derivate_00000016/a709205i.pdf:PDF},
  language = 	{en}
}