Green and efficient diazotization and diazo coupling reactions on clays

Diazotization and diazo coupling reactions of sodium sulfanilate dihydrate and para-diazonium benzene sulfonyl azide with aromatic phenols over eco-friendly clay catalysts are described. These inexpensive, noncorrosive and reusable catalysts were found to exhibit bifunctional catalytic properties for diazotization and diazo coupling reactions. No considerable decreases in the efficiency of the catalysts were observed after four cycles of operation. The new method totally avoids the use of acids, alkalies and toxic solvents in diazotization and diazo coupling reactions. (c) 2006 Elsevier Ltd. All rights reserved.