Synthesis of Functionalized Tolanes for Release of Rose Scent

The long-term objective of this research is to synthesize and develop a set of functionalized hexaphenylbenzenes capable of the controlled release of volatile fragrant molecules, otherwise known as “pro-fragrances”. The focus of current work is on the synthesis of original appropriately substituted 4,4’-diphenylacetylenes (tolanes). These tolanes may be capable of scent release and can be cyclized with catalytic amounts of cobalt octacarbonyl to form hexaphenylbenzene molecules. Efforts have focused on optimizing the conditions and yields for the production of two tolane molecules substituted in the 4,4’ positions with phenethyl ester groups. Upon hydrolysis, these ester groups will release the rose-scented 2-phenylethanol molecule. Synthesis of one tolane was accomplished through multiple steps culminating in the sequential modification of the Sonogashira coupling reaction. The required conditions (temperature, pH, time.) for the controlled hydrolysis of the tolane molecules were investigated via preliminary GC/headspace analysis and are strongly dependent on the stability of the tolane molecule.