CRYSTAL-STRUCTURE OF A TRICYCLIC PRODUCT FROM THE OXIDATION OF 4,5,6-TRICHLOROGUAIACOL WITH PERIODATE

(RS)-2,3,4',5',6'-Pentachloro-5-methoxy-1',3'-dioxaspiro [cyclohexadiene-1,2-indan]-4-one 2 has been synthesized via oxidative coupling of 4,5,6-trichloroguaiacol caused by periodic acid. The initial coupling step most probably involves the periodic ester of trichloroguaiacol or the corresponding phenoxonium ion. The primary reaction product with the trichlorocatechol formed, is stabilized by spirocyclisation to 2. The crystal and molecular structure of 2, C13H5Cl5O4, were determined by single-crystal X-ray diffraction methods. The compound crystallizes in the space group P-1(2) with the following cell dimensions: a = 9.386(5) angstrom, b = 12.028(6) angstrom, c = 14.497(10) angstrom, alpha = 68.94(4)-degrees, beta = 88.24(3)-degrees, gamma = 77.52(3)-degrees. The asymmetric unit consists of two virtually identical molecules of 2. The structure was determined by direct methods and the obtained model containing a total of 397 parameters was refined by full-matrix least-squares calculations that gave a final conventional R value of 0.042 for 3407 unique reflections with I/sigma(I) greater-than-or-equal-to 3. H-1 and C-13 NMR, IR, UV and mass spectra of 2 are all in accordance with the given structure.