Two unusual alkenes stretch the limits of molecular geometry

Some people just really enjoy pushing molecules out of their comfort zones. Neil Garg and his team at the University of California, Los Angeles, proudly count themselves among those people. Their latest work, published in in Nature Chemistry, explores the chemistry of cubene and 1,7-quadricyclene, two molecules with extremely distorted double bonds (2026, DOI: 10.1038/s41557-025-02055-9).It’s “pushing the limits of what geometric distortion looks like,” Garg says.Cubene and quadricyclene are descended from cubane and quadricylane, both cage-shaped structures with bonds that are fairly distorted from typical alkane geometries, even without a double bond in the mix. Both alkenes have been made before—quadricyclene debuted in 1979 and cubene in 1988—but nobody really did anything with them, Garg says. “They may have been a little bit ahead of their time.” Nowadays, rigid 3D structures such as cubane are highly desirable in drug discovery, making reactions to install them also desirable. And highly strained molecules are eager to undergo reactions to relieve their stress. The bonds in cubene and quadricyclene aren’t twisted like the ones in the anti-Bredt olefins that Garg’s team described in an earlier study, but they’re even more bent. Where the bonds to a normal alkene carbon all lie in a flat plane, computational modeling predicts that the bond angles in these molecules are forced out of plane by over 30°. This distortion severely weakens the bond and makes it much more reactive. The double bond in cubene has a bond order of 1.59 and the one in quadricyclene has a