Mechanisms for Manganese(III) Oxidations with Alkenes
作者:William E. Fristad、John R. Peterson、Andreas B. Ernst、Gordon B. Urbi
DOI:10.1016/s0040-4020(01)87310-5
日期:1986.1
metal complexed organic radicals, and the importance of an oxo-centered manganese(III) triangle are discussed as they relate to the lactone annulation reaction. Single electron transfer oxidation of alkenes is described as a route toward 1,2-diacetates of alkenes within the 8.1-7.5 eV I.P. range. Three less common modes of Mn(III) reaction are discussed and compared with the two primary processes of
在乙酸锰(III)与羧酸和烯烃的反应中,已经鉴定出三个不同的过程,它们涉及烯烃和两个独立于烯烃的过程。通过产品研究,重排,稀释实验和文献动力学数据的组合,可以提出一个统一的机制图来描述这些过程。具体地,讨论了羧酸组分的α-H酸的作用,缺电子的自由基加成,金属络合的有机自由基以及以氧代为中心的锰(III)三角形的重要性,因为它们与内酯环化反应有关。烯烃的单电子转移氧化被描述为通往8.1-7.5 eV IP范围内的烯烃1,2-二乙酸酯的途径。
Sonochemical switching from ionic to radical pathways in the reactions of styrene and trans-β-Methylstyrene with lead tetraacetate
The reactions of styrene and trans-β-methylstyrene with lead tetraacetate in acetic acid are greatly influenced by ultrasonic irradiation to give products resulting mostly from radical chain pathways, whereas mechanical agitation gives products only from ionic processes.
Enamines of type 1 with anion-stabilizing substituents a are available by Horner-reaction of suitable phosphonates with aldehydes. Deprotonation of 1 gives aminoallyl anions 2, which react with carbonyl compounds (depending on a) either to butyrolactones 8 resp. 10 or to 6-membered lactons 13. This process amounts to synthesis of lactones from two carbonyl compounds and an α-aminosubstituted phosphonate
best choice for the bioreduction of ethyl 2-oxocyclohexylacetate 2e, which afforded cis-(−)-5e and trans-(−)-5e with 98 and 99% e.e., respectively. Reduction of 3-(2-oxocyclohexyl)propionic acid 3e with Pichia glucozyma gave predominantly the corresponding δ-lactone trans-(−)-6e with 94% e.e., whose absoluteconfiguration was determined by means of CD spectroscopy.
The effective temperature of the radical propagation step of the ultrasonically accelerated reaction of leadtetraacetate with β-methylstyrene was thermodynamically determined as close to the ambient temperature of the bulk liquid.