High-Energy-Density Liquid Spiro-Norbornanes from Methylenenorbornane

We report a synthetic scheme for obtaining new spirohydrocarbons from a versatile norbornane derivative, methylenenorbornane. As a result, four new spiro-hydrocarbons and the isomeric-related norbornanes for the comparison have been obtained in moderate or good yields through [4 pi + 2 pi] and cyclopropanation reactions. The effect of introducing a spiro-center is dependent on the nature of carbocycles at a spiro-carbon atom. There is no obvious advantage in properties for spirocycloalkenes consisting of norbornane and cyclopropane rings at the spiro-carbon atom compared to isomeric hydrocarbons. At the same time, spirocycloalkenes with two norbornane motifs at a spiro-center have exhibited much higher values of densities and energy densities (0.992- 1.023 g/mL, 41.79-43.28 MJ/L) than the related hydrocarbons without a spiro-center and JP-10. The obtained results can provide insight and an opportunity to further expand this work to bring new high-performance jet fuels to market.