Treatment of π-allyltricarbonyliron lactone complexes, that contain an adjacent leaving group, with lithium naphthalenide causes decomplexation to acyclic dienols in excellent yield and without any stereochemical scrambling of the allylic centre. When an endo complex is employed (E,E)-geometry prevails with good selectivity whereas (Z,E)-geometry dominates in the case of exo complexes. A mechanism consistent with the observed stereo- and regiochemistry is proposed.