Photochemistry of Isopropylidene 3,3,6-Trimethyl-1,4,5-heptatriene-1,1-dicarboxylate and Its Homologues

Direct photolysis of title compounds gave alkenylidenecyclopropanes as main products, while acetone-sensitized photolysis of those led to mainly intramolecular [2+2]cycloadducts.