Co-host: The Chemical Society of Japan, The Society of Synthetic Organic Chemistry, Japan (Cooperation)
The structure of 2-norbornyl cation (1) has attracted much attention for a long time, and recent study on 1 has confirmed its nonclassical nature. However, there have been reported few studies of silicon analogue of 2-norbornyl cation; recently Muller et al. has reported the nonclassical nature of a 2-sila-2-norbornyl cation. We wish to report a theoretical study of heptasila-2-norbornyl cation (2). The study revealed a classical cation nature of 2 at B3LYP/6-31G*. The positive charge in 2 resides mostly on the 2-Silicon atom and the cation is stabilized by hyperconjugation due to β-Si-Si bond. The nonclassical structure of 2 was calculated as a transition state during the skeletal rearrengement between the two classical cations. The structural difference between 1 and 2 may be assumed to the relative unstability of Si-Si double bond. Relative stability among regio isomers of 2, we will also be discussed.
