Environmentally benign route for isomerization of safrole—hydrotalcite as solid base catalyst

Abstract

Isomerization of safrole to isosafrole is an important reaction, involving double bond migration, catalyzed by bases. Hydrotalcites, solid bases, have been used for this double bond migration. Among the catalysts studied, MgAl hydrotalcite with Mg/Al atomic ratio 6.0 showed maximum conversion of around 98% with a cis/trans isosafrole ratio of 1/9 at 200 °C using DMSO as solvent. Solvent variation studies indicated that more polar solvents favored the reaction. Variation of trivalent metal ions showed a maximum activity for hydrotalcite containing Al, followed by Fe and Cr. Bronsted basic hydroxyl groups of hydrotalcite lattice are thought to be the active centers.