SYNTHESIS AND ABSOLUTE STEREOCHEMISTRY OF CHIRAL 9,10-DIHYDRO-9,10-ETHANOANTHRACENES AND THEIR TRICARBONYLCHROMIUM COMPLEXES

Several chiral mono- and disubstituted 9,10-dihydro-9,10-ethanoanthrac enes have been prepared from the corresponding anthracenes. Most of th em were separated into enantiomers by chromatography on cellulose tria cetate (CTA) and their absolute chiralities established by chiroptical comparison (via their CD spectra) with key compounds of known configu ration. From the laevorotatory 1,5-dibromo derivative 16 the dextrorot atory dideuterio hydrocarbon (+)(9S, 10S)-20 was obtained. Complexatio n of 2,6-dimethyl 9,10-dihydro-9,10-ethanoanthracene (+)-25, obtained by enantioselective chromatography on CTA [with its chirality (9R, 10R ) deduced from optical comparison with the 2-monomethyl derivative of known configuration], with Cr(CO)6 afforded two mono tricarbonylchromi um complexes [endo)+)-26 and exo(+)-27] as well as the bis-exo,endo-co mplex (+)-28. Configurational assignments (exo, endo) are based on the absorption patterns of the bridge protons in the H-1-NMR spectra.