Experimental Evidence for Multiple Oxidation Pathways in the (salen)Mn-Catalyzed Epoxidation of Alkenes
作者:Christian Linde、Nordine Koliaï、Per-Ola Norrby、Björn Åkermark
DOI:10.1002/1521-3765(20020603)8:11<2568::aid-chem2568>3.0.co;2-z
日期:2002.6.3
the catalytic epoxidation of para-substituted cis stilbenes 2a-i were investigated by using (R,R)-[N,N'-bis(3,5-di-tBu-salicylidene)-1,2-cyclohexanediamine]manganese(III) chloride 1 in benzene as the catalyst with iodosobenzene as the terminal oxidant. A Hammett study of the selectivity results reveals a stronger electrophilic character than previously assumed in the (salen)Mn-catalyzed reaction. In
使用(R,R)-[N,N'-bis(3,5-di-tBu-Salicylidene)-1研究了底物电子对对位取代的顺式斯蒂尔苯酯2a-i催化环氧化反应选择性的影响1,2-环己烷二胺]氯化锰(III)1在苯中作为催化剂,碘代苯作为末端氧化剂。Hammett对选择性结果的研究表明,其亲电特性比以前在(salen)Mn催化的反应中所假定的要强。通常,通过使用Hammett sigma +值获得与实验值的最佳相关性,对于顺式环氧形成速率,rho = -1.37;对于逐步反应的逐步过程速率,rho = -0.43。反产品。该反应涉及两个单独的途径,这也由中间体在甲氧基取代的底物的反式环氧化物的竞争性竞争中表明。对于4-甲氧基-4'-亚硝基二苯乙烯而言,导致顺式环氧化物的协同途径中的异步性是显而易见的,由于电子效应,其完全产生具有75%ee的顺式环氧化物。