The synthesis of functionalised β- and γ-lactams by cyclisation of enamides using copper(I) or ruthenium(II)

Cyclisation of a variety of halo-enamides with copper(I) or ruthenium(II) complexes has been investigated. The regioselectivity of the radical cyclisation, which can proceed via either a 4-exo or 5-endo pathway, to form β- or γ-lactam products respectively, is determined by the nature of the metal oxidant and the reaction conditions. Thus, whereas copper(I)/bipyridine reactions give predominantly γ-lactams, the use of copper(I)/TMEDA or dichlorotris(triphenylphosphine)ruthenium(II) affords mainly β-lactams.