Under Palladium catalysis [Pd(OAc) 2 , K 2 CO 3 , LiCl, Bu 4 NBr, trans-7a-g and trans-7j, k under palladium catalysis reacted to the corresponding 9,10-bis(arylmethylene)-9,10-DMF] o-bromo-trans-stilbene (trans-7a) reacts to give 9,10dibenzylidene-9,10-dihydroanthracene (4a) with formation dihydroanthracenes 4, mostly as mixtures of (E) and (Z) diastereomers (50-97 % yield). The (Z) diastereomer of the of a new six-membered ring. The (Z) diastereomer crystallizes preferentially to give pure (Z)-4a, as proved by parent 4a and the alkyl-substituted compounds 4c and 4e could be purified by simple crystallization, and in some runs, X-ray crystal structure analysis. A variety of substituted obromostilbenes and heterocyclic analogs 7 were prepared by only (Z)-4a, c, e were obtained. Among the heterocyclic analogs trans-7h, i only the furyl derivative trans-7h reacted Wittig olefination of o-bromobenzaldehyde with substituted benzyltriphenylphosphonium ylides, Wittig-Horner-Emmons (76 % yield) cleanly, whereas the pyridine analog trans-7i gave a mixture of products from which the rather sensitive olefination of arenecarbaldehydes with diethyl obromobenzylphosphonate or Wittig olefination of substituted product 4i could not be isolated in pure form. The cis-obromostilbenes cis-7a, c cyclized to phenanthrenes under the benzaldehydes with substituted (o-bromobenzyl)diphenylphosphonium ylides, respectively. The cis-o-same conditions (70-71 % yield). The UV spectra of compounds 4a, c-k are similar to that of anthracene, and so bromostilbenes were photoisomerized to the trans diastereoisomers trans-7 by irradiation in the presence of are the oxidation and reduction potentials of (Z)-4a. diphenyl disulfide. All of these o-bromo-trans-stilbenes [ ] X-ray crystal structure analyses.
fully justified, and since the spectral data of the product