Catalytic Allylic Oxidation of Cyclic Enamides and 3,4-Dihydro-2<i>H</i>-Pyrans by TBHP
作者:Yang Yu、Ranad Humeidi、James R. Alleyn、Michael P. Doyle
DOI:10.1021/acs.joc.7b01163
日期:2017.8.18
intermediate allylic free radical two sites for oxidative product formation are possible, and the selectivity of the oxidative process varies with the heteroatom when R = H. Cyclic enamides produce 4-piperidones in good yields when R = alkyl or aryl, but oxidation of 2H-pyrans also gives alkyl cleavage products. Alternative catalysts for TBHP oxidations show comparable selectivities but give lower product
叔丁基过氧化氢(水中70%TBHP)使用己内酰胺基己二酸酯催化的[Rh 2(cap)4 ]烯丙基氧化杂烯取代的环状烯烃,形成烯酮产物,该产物具有各种2-取代的环状酰胺和3,4-二氢- 2 H-吡喃。这些反应在温和的反应条件下发生,操作上易于实施,并且对于低至0.25mol%的催化剂负载量的产物形成有效。通过中间烯丙基自由基的杂原子稳定化,可以形成两个氧化产物位点,并且当R = H时,氧化过程的选择性随杂原子而变化。当R =烷基或芳基时,环酰胺会以高收率生成4-哌啶酮,但是2的氧化H-吡喃还产生烷基裂解产物。TBHP氧化的替代催化剂显示出可比的选择性,但产物收率较低。