The Michael addition of thiols to p-quinones proceeds efficiently in water at room temperature without a catalyst. Significant rate acceleration of this reaction is observed in water compared to organic solvents. Water played a dual role in simultaneously activating the quinones and thiols. This new methodology constitutes an easy, highly efficient and green synthesis of diaryl sulfides and aryl alkyl sulfides. (c) 2007 Elsevier B.V. All rights reserved.