ISSN:
1434-193X
Keywords:
Palladium
;
Cross coupling
;
Arenes
;
Cyclizations
;
Polycycles
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Under Palladium catalysis [Pd(OAc)2, K2CO3, LiCl, Bu4NBr, DMF] o-bromo-trans-stilbene (trans-7a) reacts to give 9,10-dibenzylidene-9,10-dihydroanthracene (4a) with formation of a new six-membered ring. The (Z) diastereomer crystallizes preferentially to give pure (Z)-4a, as proved by X-ray crystal structure analysis. A variety of substituted o-bromostilbenes and heterocyclic analogs 7 were prepared by Wittig olefination of o-bromobenzaldehyde with substituted benzyltriphenylphosphonium ylides, Wittig-Horner-Emmons olefination of arenecarbaldehydes with diethyl o-bromobenzylphosphonate or Wittig olefination of substituted benzaldehydes with substituted (o-bromobenzyl)-diphenylphosphonium ylides, respectively. The cis-o-bromostilbenes were photoisomerized to the trans diastereoisomers trans-7 by irradiation in the presence of diphenyl disulfide. All of these o-bromo-trans-stilbenes trans-7a-g and trans-7j, k under palladium catalysis reacted to the corresponding 9,10-bis(arylmethylene)-9,10-dihydroanthracenes 4, mostly as mixtures of (E) and (Z) diastereomers (50-97 % yield). The (Z) diastereomer of the parent 4a and the alkyl-substituted compounds 4c and 4e could be purified by simple crystallization, and in some runs, only (Z)-4a, c, e were obtained. Among the heterocyclic analogs trans-7h, i only the furyl derivative trans-7h reacted (76 % yield) cleanly, whereas the pyridine analog trans-7i gave a mixture of products from which the rather sensitive product 4i could not be isolated in pure form. The cis-o-bromostilbenes cis-7a, c cyclized to phenanthrenes under the same conditions (70-71 % yield). The UV spectra of compounds 4a, c-k are similar to that of anthracene, and so are the oxidation and reduction potentials of (Z)-4a.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
