Regio-, Diastereo-, and Chemoselectivities in the Dioxirane Oxidation of Acyclic and Cyclic Allylic Alcohols by Methyl(trifluoromethyl)dioxirane (TFD): A Comparison with Dimethyldioxirane
作者:Waldemar Adam、Rodrigo Paredes、Alexander K. Smerz、L. Angela Valoza
DOI:10.1002/(sici)1099-0690(199802)1998:2<349::aid-ejoc349>3.0.co;2-r
日期:1998.2
regioselectivity of the geraniol epoxidation by methyl(trifluoromethyl)dioxirane (TFD) reveals that as for the less reactive dimethyldioxirane (DMD), hydrogen bonding stabilizes the transition state of the epoxidation. In protic media, the hydrogen bonding is exerted intermolecularly by the solvent, whereas in unpolar, non-hydrogen-bonding solvents intramolecular assistance through the adjacent hydroxy
甲基(三氟甲基)二环氧乙烷(TFD)对香叶醇环氧化的区域选择性的溶剂依赖性变化表明,对于反应性较低的二甲基二环氧乙烷(DMD),氢键稳定了环氧化的过渡态。在质子介质中,氢键由溶剂在分子间施加,而在非极性,非氢键的溶剂中,通过相邻羟基官能团的分子内辅助起作用,并且有利于对烯丙基醇部分的攻击。对于手性烯丙基醇,另外的空间相互作用在构象固定的过渡态中控制π-面选择性。与DMD相似,TFD环氧化的氢键过渡态中的优选二面角约为130°,此处研究的1和3-5被TFD化学选择性环氧化而未形成相应的烯酮。