Beta-electrophilic additions of pentaamineosmium(II) eta(super 2)-pyrrole complexes

A study of the reactivity of 4,5-eta(super 2)-pyrrole complexes shows that these complexes undergo electrophilic addition reactions to form beta-substituted pyrroles. Reaction with alpha,beta-unsaturated carbonyl compounds results in the formation of 1,3-dipolar cycloaddition adducts that ring-open to form alpha-substituted pyrrole with osmium at 3,4 position. Combination of pyrrole complexes with alkyne Michael acceptors helps in capturing the iminium carbon of the 3H-pyrrolium species to form metalated cyclobutene derivatives.