Ionic liquids-promoted addition of arylsulfinic acids to p-quinones:: A green synthesis of diaryl sulfones

Arylsulfinic acids undergo smooth conjugate addition to p-quinones in air- and moisture-stable second generation room temperature ionic liquid [bmim]BF4 under mild conditions to produce the corresponding arylsulfonylhydroquinones in excellent yields with high selectivity. In this reaction, ionic liquid plays the dual role as the solvent and the catalyst. The quinones show enhanced reactivity in ionic liquid thereby reducing the reaction times and improving the yields significantly. The presence of ionic liquids helps to avoid the use of either acid or base catalysts for this conversion. The recovered ionic liquid was reused for four to five times with consistent activity.