Benzaldehyde and a methyl sulfide, formed from the thiol used, are two major products of the title reaction in methoxyethanol. Primary alkyl thiols were less active than secondary ones, but the most active system was obtained with an aryl thiol, benzenethiol. Therefore, detailed studies were carried out with it. The reaction towards benzaldehyde and the methyl sulfide proceeded only in the presence of iron porphyrins. When the catalyst degraded, only side reactions, disulfide formation and anti-Markovnikov addition occurred. Thiols do not act as sacrificial reductants in the studied system. UV-Vis spectra revealed the formation of an iron(III) porphyrin radical cation. It was present only in the active phase of the reaction. Since it was formed with some delay, it did not make an intermediate of the studied reaction but seemed to be in equilibrium with it. (C) 2002 Elsevier Science B.V. All rights reserved.