145238-26-2Relevant academic research and scientific papers
Hypervalent iodine initiated intramolecular alkene dimerisation: A stereodivergent entry to cyclobutanes
Zhu, Yuxiang,Colomer, Ignacio,Donohoe, Timothy J.
supporting information, p. 10316 - 10319 (2019/09/03)
The emergence of new methods for the stereoselective synthesis of strained carbocycles is a challenging but worthwhile endeavour. Cyclobutanes, in particular, have attracted the attention of both medicinal chemists and material scientists for their unique properties. Herein, we present a new method that allows access to highly functionalized cyclobutanes with complementary all-trans and trans-cis-trans relative stereochemistry, that could not be accessed before. This approach consists of an intramolecular dimerisation of non-conjugated dienes using an oxidative single electron transfer (SET) process, and is initiated by catalytic amounts of hypervalent iodine reagents. The potential uses of these cyclobutanes is demonstrated with selective functionalization, including the formation of diols and carboxylic acids.
Is hole transfer involved in metalloporphyrin-catalyzed epoxidation?
Kim, Taisun,Mirafzal, Gholam A.,Liu, Jianping,Bauld, Nathan L.
, p. 7653 - 7664 (2007/10/02)
The possibility of a hole-transfer mechanism for the epoxidation of alkenes catalyzed by metalloporphyrins (MP) has been investigated. In the first approach, the results of MP-catalyzed epoxidation of a series of substrates were compared to the corresponding results of epoxidation under conditions where cation radicals are demonstrably formed (using a triarylaminium salt catalyst). In sharp contrast to the MP-catalyzed epoxidations (using M = Mn), the hole-catalyzed epoxidations do not generate carbonyl compounds and alcohols as byproducts and are rigorously stereospecific. These results are of interest primarily in that they provide support for the assumption that cation radicals can be efficiently and stereospecifically epoxidized by appropriate oxygen-transfer agents. However, the differences in product composition and stereochemistry for MP- vs hole-catalyzed epoxidation cannot be construed mechanistically to rule out a cation radical mechanism for the former, especially because the oxygen-transfer agents are different in the two reaction systems. In a second, and more rigorous, approach, a careful search for transient cation radical intermediates in MP-catalyzed epoxidations (using M = Mn and Fe) was carried out using newly developed cation radical probe reactions. Cation radical intermediates were, in fact, not detected and, if involved, must be extremely short lived (-2 s). The results of this work, taken as a whole, are reasonably construed to suggest that, even for the relatively easily ionizable alkene functionalities present in many of the probe substrates, a hole-transfer mechanism is probably not operative in MP-catalyzed epoxidations.
