Development of Efficient and Selective Processes for the Synthesis of Commercially Important Chlorinated Phenols

para-Selective processes for the chlorination of phenols using sulphuryl chloride in presence various sulphur-containing catalysts have been successfully developed. Several chlorinated phenols, especially those derived by para-chlorination phenol, ortho-cresol, meta-cresol, and meta-xylenol, are significant commercial importance, but reactions such not always as regioselective would be desirable. We, therefore, undertook challenge developing suitable that might promote greater regioselectivity under conditions still applicable manufacture products on a large scale. In this review, we chart our progress endeavour from early studies involving inorganic solids potential catalysts, through use simple dialkyl sulphides, which were effective unsuitable application, variety other types sulphur compounds, to eventual identification particular poly(alkylene sulphide)s very useful catalysts. When used conjunction with Lewis acid aluminium or ferric an activator, reagent, quantitative yields chlorophenols can obtained high tiny amounts polymeric usually solvent-free (unless phenol starting material is solid at temperatures even above about 50 °C). Notably, containing longer spacer groups particularly para-selective m-cresol m-xylenol, while, ones shorter spacers 2-chlorophenol, o-cresol. Such result some highest para/ortho ratios reported phenols.