Meet The Ivyanes

Chemists in Australia have given birth to a new family of hydrocarbons: the ivyanes. These oligocyclopropanes feature triangular rings hanging off the side of a carbon chain, a structure that resembles leaves on an ivy vine (Chem. Sci., DOI: 10.1039/c0sc00500b). In 2009, Michael S. Sherburn and coworkers at Australian National University reported the synthesis of dendralenes, a class of compounds in which each carbon in a chain is part of a branching alkene ideally situated to undergo cyclopropanation. Sherburn’s group has now used the Simmons-Smith reagent (diiodomethane and diethylzinc) to convert dendralenes with from three to eight alkenes to the corresponding ivyanes. The reactions are a chemical tour de force. For example, conversion of [8]dendralene to [8]ivyane involves formation of 16 C–C bonds. The shorter chain ivyanes are liquids at room temperature, whereas the [7] and [8] versions are solids. The compounds adopt chiral helical conformations in both solution and solid phases, a property that could be exploited in multiple applications. In addition, the unique ivyane framework prompted the team to try ring-opening reactions, which led to dimethyl-substituted chains with contiguous quaternary carbons, structures that are normally tough to make.