A straightforward synthesis of (E)-δ-alkenyl-β,γ-unsaturated δ-lactones by a tandem ring-closing/cross-coupling metathesis process

The access to (E)-δ-alkenyl-β,γ-unsaturated δ-lactones starting from 3-O-(1,4-pentadienyl) 3-butenoate has been investigated by using a tandem process including two different metathesis reactions. By this way, new structures, isomers of natural compounds like argentilactone, were isolated in good yields. Reconjugation of the internal CC bond can be achieved under basic conditions to give α-pyrones.