Acetal formation by metal ion-mediated desulfurization-condensation of thioketones with diols and phenols

Article abstract of DOI:10.3987/COM-95-7375

The acetal formation of thioketones with several diols and phenols through metal ion-mediated desulfurization-condensation was investigated. The reactivities of 4,4′-bis(dimethylamino)thiobenzophenone) "thio-Michler's ketone" (TMK) and xanthene-9-thione (XT) toward α,ω-alkanediols [HO(CH2)nOH, n = 2～4] in the presence of silver trifluoroacetate and triethylamine were compared. The reaction of TMK with glycerol, trans- and cis-1,2-cyclohexanediols, α,α'-dihydroxy-o-xylene and biphenyl-2,2-diol in the presence of silver salt gave the corresponding acetals in good yields. On the other hand, copper(I) chloride, in place of silver(I) salt, was useful for catechol and pyrogallol to give their acetals, respectively. It was thus found that thioketones are new and versatile acetalizing reagents for diols and phenols.