Tandem Long Distance Chain-Walking/Cyclization via RuH2(CO)(PPh3)3/Bronsted Acid Catalysis: Entry to Aromatic Oxazaheterocycles

A novel route to 1,3-oxazaheterocycles based on cooperative RuH/Bronsted acid catalysis is reported. The use of the commercially available RuH2(CO)(PPh3)(3) complex allows for an efficient long distance chain-walking process while the Bronsted acid is responsible for generation of an electrophilic iminium ion which is trapped intramolecularly by an alcohol moiety. The alcohol, besides its nucleophilic function, also plays an important role in the stabilization of the Ru catalyst.