A preliminary investigation into optimal conditions for allylic nucleophilic replacement

Reactions involving allylic leaving groups are problematic due to the leaving group being proximal to the carbon-carbon double bond. The proximity of the carbon-carbon π-bond system frequently leads to rearrangement products. In view of the potential occurrence and utility of such compounds in organic synthesis, it is the broader objective of this research to seek out leaving groups, which may be manipulated and utilized with product control. Examples of such variations include solvent systems, choice of base, sequence and timing of reagents, reaction time, and temperature. By selecting optimal leaving groups and tuning reaction conditions, we hope to achieve nucleophilic replacement without rearrangement or elimination. Ideally, we seek replacement at the carbon bearing the leaving group rather than on another carbon. Examples of possible leaving groups are tosylates and trifluoroacetates, which were chosen for the stability of the corresponding tosylate and trifluoroacetate ions as estimated by the pKₐ of their corresponding acids (-2.86 and 0.23, respectively). The model alcohols used for the preparation of the tosylate and trifluoroacetate esters were cinnamyl alcohol and isophorol. Cinnamyl alcohol was chosen because it possesses an aromatic ring and has a double bond on the alkyl chain, which prevents any elimination to dienes. Isophorol was chosen due to its easy reduction from the readily available and inexpensive isophorone. Although its structure can lead to elimination to dienes, it allows for a thorough study in finding ideal reaction conditions.