The synthesis and study of tricyclo[3.3.3.0p3s,̳ p7s] undec-3(7)-ene, an important member of a homologous series of pyramidalized olefins

Abstract

This dissertation describes the 17-step synthesis and study of tricyclo (3.3.3.0$\sp{3,7}$) -undec-3(7)-ene. It is, indeed, a very important member of a homologous series of pyramidalized olefins, because, unlike lower members of this series, it can be isolated and studied at room temperature. The stability of this olefin has allowed its $\sp$C NMR spectrum to be obtained, and the spectrum shows unequivocally that pyramidalization results in a downfield shift of the resonance for the olefinic carbons. The temperature dependence of both the $\sp$C and $\sp1$H NMR spectra indicate that the olefin undergoes a dynamic conformational change that involves flipping of the trimethylene bridge. The same process is evident in the NMR spectra of several precursors of the olefin; and the values of $\Delta$G$\sp\ne$ that are measured and the results of molecular mechanics calculations both indicate that twisting about the C$\sb3$-C$\sb7$ bond facilitates this conformational change. The photoelectron and electron transmission spectra of the olefin confirm the computational prediction that pyramidalization lowers the energy of the lowest unoccupied orbital of an olefin much more than it raises the energy of the highest occupied orbital. Not only is the synthesis of the olefin significant for the new information about the effects of olefin pyramidalization that it has already furnished, it is also important because of the future studies of this molecule that its successful preparation has made possible.