Water was used as the solvent in the Petasis borono-Mannich reaction. With the use of salicylaldehyde, secondary amines and boronic acids, several alkylaminophenols were obtained in considerably high yields in water. By using the same methodology, 2H-chromenes were prepared with the use of vinyl boronic acids. The reaction mechanism was studied by DFT calculations, and the results obtained corroborate the solvent effect experimentally observed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009). - Fundacao para a Ciencia e Tecnologia [POCI 2010]; FEDER [SFRH/BPD/46589/2008PTDC/QUI/66695/2006, PTDC/QUI/66015/2006, POCI/QUI/60175/2004, POCI/QUI/58791/2004]. - We thank the Fundacao para a Ciencia e Tecnologia (POCI 2010) and FEDER (SFRH/BPD/46589/2008PTDC/QUI/66695/2006, PTDC/QUI/66015/2006, POCI/QUI/60175/2004, POCI/QUI/58791/2004) for financial support.