Lewis Acid-Catalyzed Alkylation of Azulene Derivatives with Epoxides and Oxetanes: A Regioselective Approach to Functionalized Azulene Alcohols

Upon treatment with a catalytic amount of BF₃·OEt₂, the reaction between azulene derivatives and epoxides efficiently affords azulenylethanol derivatives. In most cases, this ring-opening transformation proceeds with high regioselectivity, favoring nucleophilic attack at the more substituted position of the epoxide. Stereochemical studies support an S_N2-type mechanism for the transformation. Furthermore, a preliminary investigation revealed that appropriately substituted oxetanes can also participate in this ring-opening reaction, delivering the corresponding homologated alcohols under similar catalytic conditions.