The Cyclopropane-Mediated Ring-Expansion of [4.3.1]Propellenes. A New Route to [5.3.1]Propelladienes

The [5.3.1] propelladiene (1) has been synthesized in six steps from the readily available [4.3.1] propellene (10a). Epoxidation of (10a) gives oxide (11a) which undergoes base-promoted rearrangement to allylic alcohol (12a). Simmons-Smith cyclopropanation of (12a) then gives the tetracyclic alcohol (13a). Mild thermolysis of the derived mesylate (14a) affords the ring-expanded isomer (20) which reacts with 1,8-diazabicyclo [5.4.0]undec-7-ene to give diene (1). A similar sequence of reactions has been used in the preparation of dienol (2) from acetal (10b). Compounds (1) and (2) react with 4-phenyl-4H-1,2,4-triazoline- 3,5-dione to give the Diels-Alder adducts (29a) and (29b) respectively.