2,2,6,6-Tetramethylpiperidine-catalyzed, ortho-selective chlorination of phenols by sulfuryl chloride

Abstract

2,2,6,6-Tetramethylpiperidine (TMP)-catalyzed (1- 10%) chlorinations of phenols by SO2Cl2 in aromatic solvents are more ortho selective than with primary and less hindered secondary amine catalysts. Ortho-selective chlorination is successful even with electron deficient phenols such as 2-hydroxybenzaldehyde and 2'- hydroxyacetophenone. Notably, ortho selectivity increases with the reaction temperature. On the other hand, tetraalkylammonium chloride-catalyzed chlorinations are moderately para selective. © 2013 American Chemical Society.