The study of the synthesis of a number of strained molecules, termed "fenestranes and/or fenestrenes" in this investigation will improve the understanding of the bonding character in such compounds. The synthesis and study of the 12 pi annulene (staurane-1,3,5,7,9,11-hexaene) and the 14 pi-?5.5.6.6.! fenestrane heptaene are important in terms of the bonding character of carbon. In the approach toward "planarization" of tetrahedral carbon, the targets have been chosen to provide a gradual increase in bond angle deformation/strain energy for purposes of comparision. Initial research will focus on the synthesis of the ?5.5.5.5!fenestranes, (tccc) and (tctc), as well as ?5.5.6.6!fenestrenes. Knowledge gained from synthesis of the above molecules will then be employed for the study of the more reactive ?5.5.5.5!fenestrenes. In addition, investigation of the synthesis of fenestrane annulenes will help to determine if Huckel pi-delocalization plays a role in the stability of such polyquinene annulenes; these annulenes are primarily composed of fused five-membered rings. Calculations at various levels of sophistication for a variety of these fenestranes have provided accurate bond lengths and bond angles where comparison with X-ray structures is possible, there are no experimental thermochemical data in strained systems for evaluation of the accuracy of the computational methods. Studies of the chemistry/reactivity of the target molecules will provide much needed insight into the nature of the carbon chemical bond in organic molecules in general, and in particular with respect to carbon atoms where strain and angle deformation may effect a change in hybridization. The Organic Synthesis Program is supporting the continuation of the studies of Dr. James M. Cook. The research will provide greater understanding of the effect of strain upon the carbon framework by the construction of molecules which have highly distorted structures. This has the potential to provide deeper insight into how chemical reactivity can be usefully manipulated.
