哌啶氧铵盐对醇氧化反应的活性和选择性

系统地研究了12种具有不同4-位取代基(R=H、CH~3O、Cl)及反离子(X=Cl、BF~4、ClO~4、Br或Br~3)的2, 2, 6, 6-四甲基哌啶氧铵盐对醇的氧化反应, 发现这些氧铵盐都能以很高的由率将一级醇氧化为醛, 二级醇氧化为酮。氧化反应的活性与4-位取代基及反离子有关。当反离子相同时, 反应活性的顺序为Cl>CH~3O>H;当4-位取代基相同时, 反应活性的顺序为Cl^-》BF~4^->ClO~4^->Br^-。氧化反应的选择性主要与反离子有关, 当反离子为Cl^-时, 主要氧化一级醇; 当反离子为BF~4^-、ClO~4^-、Br^-或Br~3^-时, 主要氧化二级醇。

Reactivity and selectivity in the oxidation of alcohols by oxoammonium salts

Systematic study was performed on the oxidation of alcs. by twelve 2,2,6,6-tetramethylpiperidine oxoammonium salts I (R = H, MeO, Cl; X = Cl, BF4, ClO4, Br or Br3). All of these oxoammonium salts can oxidize primary alcs. to aldehydes and secondary alcs. to ketones with very high yield. The reactivity of the oxidants is related with both the 4-substituent and the counter-ion with the sequence of Cl > MeO > H for the salts with the same counter-ion and Cl- ?BF4- > ClO4- > Br- for the salts with the same 4-substituent. The selectivity of the oxidants is mainly determine by the counter-ions. The oxidant oxidizes preferably primary alcs. when the counter-ion is Cl-, but oxidizes secondary alcs. selectively when the counter-ions are BF4-, ClO4-, Br- or Br3-.