Electroactive protecting groups and reaction units. Part 4. Mesolytic O–CO bond cleavage versus intramolecular cyclization reaction in enol trifluoroacetate cation radicals. A kinetic and mechanistic investigation
摘要:
The one-electron oxidation of two beta,beta-dimesityl enol trifluoroacetates with different substituents R at C-alpha was investigated. For the first time enol trifluoroacetate cation radicals could be reversibly monitored in cyclic voltammetry experiments allowing the determination of the rate constants of their follow-up reactions. While mesolytic cleavage of the O-CO bond (k(f) = 1.4 s(-1)) with direct formation of an alpha-carbonyl cation constitutes the primary reaction of the enol trifluoroacetate cation radical with R = Bu(t), the one with R = Ph exclusively cyclizes (k(f) = 75 s(-1)) to a phenanthrene derivative. This change in reactivity can be rationalized by the different nature of the electrophoric system as a function of the substituent R.
Electroactive protecting groups and reaction units. Part 4. Mesolytic O–CO bond cleavage versus intramolecular cyclization reaction in enol trifluoroacetate cation radicals. A kinetic and mechanistic investigation
作者:Michael Schmittel、Holger Trenkle
DOI:10.1039/p29960002401
日期:——
The one-electron oxidation of two beta,beta-dimesityl enol trifluoroacetates with different substituents R at C-alpha was investigated. For the first time enol trifluoroacetate cation radicals could be reversibly monitored in cyclic voltammetry experiments allowing the determination of the rate constants of their follow-up reactions. While mesolytic cleavage of the O-CO bond (k(f) = 1.4 s(-1)) with direct formation of an alpha-carbonyl cation constitutes the primary reaction of the enol trifluoroacetate cation radical with R = Bu(t), the one with R = Ph exclusively cyclizes (k(f) = 75 s(-1)) to a phenanthrene derivative. This change in reactivity can be rationalized by the different nature of the electrophoric system as a function of the substituent R.