Tetrabutylammonium Hydroxide: A Reagent for the Base-Catalyzed Dehydration of Vicinal Dihydro Diols of Aromatic Hydrocarbons. Implications to Ion-Pair Chromatography

Article abstract of DOI:10.1021/jo00334a010

Vicinal dihydro diols of benzopyrene and benzanthracene are dehydrated to their phenolic derivatives by the methanol eluate of reverse-phase (octadecylsilane) columns previously treated with tetrabutylammonium phosphate.Phenols are also produced by treating the dihydro diols with methanolic tetrabutylammonium hydroxide on removal solvent.In most cases the regioselectivity is markedly different from the acid-catalyzed dehydration.The in situ generated tetrabutylammonium phenoxides are converted to the butyl ethers at high temperatures (150 deg C) but not under th e conditions of dehydration (60 deg C).Tetraethylammonium and tetramethylammonium hydroxides also dehydrate dihydro diols, whereas potassium and sodium hydroxides do not.Dehydration does occur by treatment of dihydro diols with potassium hydroxide in the presence of 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) and with sodium methoxide in the presence of tetrabutylammonium chloride.A mechanism is suggested.