合成了四十个在卟啉环上具有不同外围取代基(R)的金属卟啉RTPPM III Cl和[RTPPM III ] 2 O(M = Fe,Mn),并用于在温和条件下用碘代苯催化环己烷羟基化。证明在环己烷羟基化的速率常数k和卟啉环上取代基的Hammett常数σ之间存在哈米特关系(log k = ρσ + c)。反应常数ρ的值金属卟啉催化的环己烷氧化反应从0.3变为0.5,并且吸电子基团提高了反应速度。这意味着反应介质是自由基阳离子,并且反应的速率确定步骤是自由基反应。这些研究结果为金属卟啉催化烃羟基化过程中的高价含氧金属自由基阳离子中间体和氢自由基提取机理提供了新的证据。
A Green Process for Oxidation of p-Nitrotoluene Catalyzed by Metalloporphyrins under Mild Conditions
摘要:
A novel synthetic technology of p-nitrobenzoic acid has been investigated with dioxygen by using metalloporphyrins RTPP-(MCl)-Cl-III (M = Fe, Co, Mn) as biomimetic catalysts. Oxidation of p-nitrotoluene to p-nitrobenzoic acid under 2.0 MPa of O-2 in the presence of a microamount of metalloporphyrins (RTPP-(MCl)-Cl-III) at 55 degrees C was achieved with the highest ( up to 90.4%) yield. Further research results show that the catalytic activities were relative to the nature of the substituted groups and the central metal ions of metalloporphyrins. For the metalloporphyrins with the same center metal ions, the greater the electron-withdrawing degree of groups in the porphyrin ring, the higher the catalytic activities of the metalloporphyrins. The catalytic activities for metalloporphyrins with different center metal ions followed the order RTPPMn Cl-III > RTPP (FeCl)-Cl-III > RTPP (CoCl)-Cl-III.