Avoiding Olefin Isomerization During Decyanation of Alkylcyano α,ω-Dienes: A Deuterium Labeling and Structural Study of Mechanism

A two-step synthetic pathway involving decyanation chemistry for the synthesis of pure alkyl α,ω-dienes in quantitative yields is presented. Prior methodologies for the preparation of such compounds required 6−9 steps, sometimes leading to product mixtures resulting from olefin isomerization chemistry. This isomerization chemistry has been eliminated. Deuteration labeling and structural mechanistic investigations were completed to decipher this chemistry. Deuterium labeling experiments reveal the precise nature of this radical decyanation chemistry, where an alcohol plays the role of hydrogen donor. The correct molecular design to avoid competing intramolecular cyclization, and the necessary reaction conditions to avoid olefin isomerization during the decyanation process are reported herein.