Use of fluoroalkyl as a latent group for internal alkylation: application to the synthesis of bridged tetrahydrofluorenones.

Tetrahydrofluorenones which possess a C9a-fluoroalkyl substituent were efficiently converted to tetrahydrofluorenones which contain a ring bridging C9a-C2. Conditions include a stepwise sequence of conversion to an alkyl bromide followed by treatment with base, and a direct cyclization by treatment with lithium chloride in DMF heated to 150 degrees C.