One-pot ruthenium catalyzed synthesis of spiro[pyrrolidin-2-one] derivatives by a [2+2+1] cycloaddition of ketimines, carbon monoxide and ethylene

The reaction of chiral N,N'-bis(aryl)tetrahydropyrrolo[2,1-c][1,4]oxazine-3,4-diylidenediamines with carbon monoxide and ethylene in the presence of a catalytic amount of Ru-3(CO)(12) leads to the formation of spiro-lactams by a formal [2 + 2 + 1] cycloaddition reaction, whereas the imine double bond next to the oxazine nitrogen atom remains unreacted; the same spiro-lactams may be synthesized if iron carbonyl complexes of the N,N'-bis(aryl)tetrahydropyrrolo[2,1-c][1,4]oxazine-3,4-diylidenediamines are introduced as the starting compounds.