HELICALLY CHIRAL THIA-QUINQUEPHENYLOPHANES AND DISELENA-QUINQUEPHENYLOPHANES

Helically chiral thia- and diselena-quinquephenylophanes have been syn thesized starting from suitable benzene derivatives via an 8-step synt hesis path. Helical thiaquinquephenylophane 9 was obtained from bis(br omomethyl)quinquephenyl 8 in cyclisation with thioacetamide under high -dilution conditions in 10% yield. The corresponding diselenaquinqueph enylophane was obtained in 17% yield by using KSeCN and reduction. The M- and P-enantiomers of the thiaphane were separated by HPLC using th e Okamoto resin. The CD and UV spectra of the pure M- and P-enantiomer s of the thiaphane were recorded. X-Ray structure analyses of the race mic crystals were performed for both compounds. Unit-cell parameters: 9, a = 10.952(1), b = 11.896(2), c = 9.804(1) Angstrom, alpha = 104.19 (1), beta = 111.71(1), gamma = 80.19(1)degrees, V = 1146.0(3) Angstrom (3); 10, a = 10.304(2), b = 15.204(4), c = 9.128(1) Angstrom, alpha = 105.08(2), beta = 113.72(1), gamma = 93.41(2)degrees, V = 1242.2(5) An gstrom(3). In addition, a dimeric selena-bridged [3.3] quinquephenylop hane was observed, and its presence confirmed by FAB-MS and Se-77 NMR spectroscopy.