Activation of the Ketone of 5-Cyclodecenones Towards Thermal Transannular Cyclization to Give Trans-Hydroazulenols

The cyclization of 5-cyclodecenones substituted at C2 with an alkoxy group was examined. The alkoxy group sufficiently activates the ketone to allow for transannular cyclization upon heating, leading to trans fused hydroazulenols. In the cyclization of the 6-(trimethysilyl)methyl substituted 5-cyclodecenone, the TMS of the allylsilane is retained in the product, leading to a vinylsilane product. Both the thermal and acid-induced cyclizations lead to products with a trans relationship between the oxygen substituents.