Regiodivergent Cyclobutanone Cleavage: Switching Selectivity with Different Lewis Acids

The exploitation of strain release in small rings as driving force to enable complex transformations is a powerful synthetic tool. Among them, cyclobutanones are particularly versatile substrates that can be elaborated in a wide variety of structurally diverse building blocks. Herein, Lewis acid catalyzed rearrangement reactions are presented that provide selective access to two structurally distinct polycyclic scaffolds, that is, indenylacetic acid derivatives and benzoxabicyclo[3.2.1]octan‐3‐ones. The choice of the Lewis acid fully controls the reaction pathway and the regioselectivity of the cyclobutanone C?C bond cleavage site.