Aqueous Catalytic Pauson–Khand‐Type Reactions of Enynes with Formaldehyde: Transfer Carbonylation Involving an Aqueous Decarbonylation and a Micellar Carbonylation

One rhodium(I) complex catalyzes two processes in an overall Pauson–Khand-type reaction of enynes such as 1 with formaldehyde in an aqueous medium to give bicyclic cyclopentenones such as 2 in excellent yields. The use of a water-soluble phosphane ligand in conjunction with a hydrophobic phosphane ligand in the presence of a surfactant promotes the decarbonylation of formaldehyde in the aqueous phase and the carbonylation of enynes in the micellar phase.