Abstract Cross-coupling between 3-buten-2-ol (2) and aldehyde in the presence of a catalytic amount of [RuCl 2 (PPh 3) 3] has been developed, through a tandem olefin migration/aldol reaction in a water/toluene mixture. The presence of In (OAc) 3 promoted the aldol reaction with α-vinylbenzyl alcohol (4) and aldehyde, while treatment of 3-buten-2-ol (2) with imines generated Mannich-type reaction products; syn isomers were formed as ...