Crystal structures of 3,6-di­allyl­tetra­cyclo[6.3.0.04,11.05,9]undeca-2,7-dione and 1,7-di­allyl­penta­cyclo­[5.4.0.02,6. 03,10.05,9]undecane-8,11-dione: allyl­ated caged compounds

The title compounds, C17H20O2 (1) and C17H18O2 (2), are allyl-ated caged compounds. In (1), the carbon atoms bearing the allyl groups are far apart [2.9417 (17) Å], hence the expected ring-closing metathesis (RCM) protocol failed to give a ring-closing product. When these carbon atoms are connected by a C-C bond as in (2), the distance between them is much smaller [1.611 (3) Å] and consequently the RCM process was successful. The caged carbon skeleton of (1) can be described as a fusion of four five-membered rings and one six-membered ring. All four five-membered rings exhibit envelope conformations. The structure of compound (2) consists of four five-membered rings, of which two are cyclo-penta-none rings bonded at the 2, 4 and 5 positions and linked at the 3-carbons by a methyl-ene bridge. It also consists of one four-membered and two six-membered rings. All four five-membered rings adopt envelope conformations. In the crystal of (1), mol-ecules are linked via C-H⋯O hydrogen bonds, forming sheets lying parallel to (010). In the crystal of (2), mol-ecules are linked via C-H⋯O hydrogen bonds forming chains along [100].