UCLA chemists have found a big problem with a fundamental rule of organic chemistry that has been around for 100 years—it's just not true. And they say, It's time to rewrite the textbooks.
“The rule in question, known as Bredt’s rule in textbooks, was reported in 1924. It states that molecules cannot have a carbon-carbon double bond at the ring junction of a bridged bicyclic molecule, also known as the “bridgehead” position. The double bond on these structures would have distorted, twisted geometrical shapes that deviate from the rigid geometry of alkenes taught in textbooks.
…A paper published by UCLA scientists in the journal Science has invalidated that idea. They show how to make several kinds of molecules that violate Bredt’s rule, called anti-Bredt olefins, or ABOs, allowing chemists to find practical ways to make and use them in reactions.”
Anti-Bredt double bonds have been a thing for a long time. Taxol (Paclitaxol) comes to mind.
Sorry if this is touched on in the article. I’m going to read it now.