REACTIONS OF ACETYLENIC GAMMA-GLYCOLS .35. SYNTHESIS, SPECTRAL PROPERTIES AND PLAUSIBLE FORMATION MECHANISM OF TETRAARYLCYCLO-BIS-[3]-CUMULENES

Analogs of tetraphenylcyclo-bis-butatriene (10) with electron acceptor or electron donor substituents at pam position of the phenyl rings ha ve been obtained from corresponding symmetric acetylenic gamma-glycols by treatment with hydrogen iodide in statu nascendi. The electron don or effect of the methoxy group causes that the tetraanisyl derivative (12) can be formed already during the obtaining of 1,4-diol (6) by the Grignard method (spontaneous dehydration during hydrolysis). The mech anism of formation of the title compounds has been discussed. UV/Vis, IR, H-1 and C-13 NMR data for substrates and products are given as wel l as MS data for the latter. A batochromic effect of substituents in e lectronic spectra was observed. A doubling of methyl groups protons si gnals occurs in H-1 NMR spectra of diastereoisomer mixtures of acetyle nic 1,4-diols. A comparison of C-13 NMR spectra of the title compounds with linear [3]-cumulenes has been made. Fragmentation of the title c ompounds (MS spectra) leads to corresponding divinylacetylenes (molecu le splitting by half, dominating process).