Acetal Formation by Metal Ion-mediated Desulfurization-Condensation of Thioketones with Diols and Phenols

The acetal formation of thioketones with several diols and phenols through metal ion-mediated desulfurizationcondensation was investigated The reactivities of 4.4'-bis(dimethylamino)thiobenzophenone, "thio-Michler's ketone" (TMK) and xanthene-9-thione (XT) toward a,walkanediols [HO(CH2)nOH, n = 2-41 in the presence of silver nifluoroacetate and methylamine were compared.The reaction of TMK with glycerol, trans-and cis-1,2-cyclohexanediols, a,aS-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, coppefl) chloride, in place of silver(1) 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.Divalent sulfur compounds have strong affinity with silveru) ion.We have been trying to apply this interaction to the field of organic synthesis.In the previous paper] we reported on the silver(1) ion-mediated desulfurization-condensation between thiocarbonyl compounds and nucleophiles such as active methylene compounds, anilines, and ethylene glycol, and found that most reactions proceed smoothly at room mmol) was mated for one hour in the same manner as above to give 44'-dimethylaminoknzophenone (72 mg, 93%).