The monoepoxidation of acyclic, conjugated aliphatic dienes by dimethyldioxirane: kinetics

[摘要] Kinetic data for the reaction of dimethyldioxirane ( 1 ) with a series of acyclic, aliphatic conjugated dienes 2a–f are reported. Monoepoxidation is the preferred process and the monoepoxides are formed in high yield as long as the dienes are in excess. The results show that epoxidation of the dienes is less sensitive to structural effects than that for simple alkenes. Furthermore, these monoepoxidations show little sensitivity to cis / trans substitution in marked contrast to those of simple aliphatic alkenes. The relative reactivities were modeled using a density function approach. Consistent with previous calculations on alkene systems, a concerted process with a spiro transition state was obtained for diene epoxidation regardless of the initial orientation of the reactants. The relative reactivities for monoepoxidation of 2c–e were calculated based on the weighted average of the calculated differences between E calc for reaction of the s - cis and s - trans conformer of each diene with 1 . The predicted relative reactivities were in reasonable agreement with those from the kinetic data.

[学科分类] 内科医学

[关键词] dimethyldioxirane;epoxidation;kinetics