Boric acid acts as an efficient catalyst for the conjugate addition of aliphatic thiols, dithiols and aromatic thiols to alpha,beta-unsaturated nitriles, esters, ketones and aldehydes with very good yields in water at room temperature. The reactions are faster in MeOH or EtOH. The use of boric acid, being a safe chemical, as the catalyst and water as the reaction medium are important attributes in the present protocol. (c) 2007 Elsevier B.V. All rights reserved.