Bending the rules for twisted double bonds

Organic chemist Neil A. Garg and his team at the University of California, Los Angeles, love testing the limits of what molecules can do. Their latest paper upends Bredt’s rule , a 100-year-old guideline that applies to molecules called bridged compounds. These molecules contain two rings that have more than one side in common, giving them a peaked shape. The rule says it is impossible for these compounds to have a double bond connected to the carbon at the junction between the rings because the bond would have to be twisted and bent far outside its usual planar arrangement, a configuration that would lead to a huge amount of strain. Garg and his team showed that these molecules, called anti-Bredt olefins, are not only possible to make but potentially useful for chemists interested in constructing complex 3D molecules ( Science 2024, DOI: 10.1126/science.adq3519 ). “I think maybe impossible will go