Efficient synthesis of spirolactones from cyclic anhydrides via an allylation/alkylation-RCM sequence

Starting from cyclic anhydrides the diallyl or dibutenyl lactones were obtained. The ring closing metathesis reaction of these using the Grubbs catalyst provided the corresponding spirolactones in good yields. With diallyl δ-lactone 2h, RCM occurred only in the presence of titanium tetraisopropoxide.