625-31-0Relevant articles and documents
Total synthesis of (–)-cephalosporolide D
Kalavakuntla, Chiranjeevi,Kummari, Vijaya Babu,Yadav, Jhillu Singh
, (2021/03/22)
In this communication, a concise and efficient synthetic route for the synthesis of (–)-Cephalosporolide D in enantioselective way has been described. In this synthesis, Mitsunobu esterification and Ring Closing Metathesis (RCM) for macrocyclic ring formation have been applied as key steps.
Dialkyl Ether Formation at High-Valent Nickel
Le Vaillant, Franck,Reijerse, Edward J.,Leutzsch, Markus,Cornella, Josep
supporting information, p. 19540 - 19550 (2020/12/01)
In this article, we investigated the I2-promoted cyclic dialkyl ether formation from 6-membered oxanickelacycles originally reported by Hillhouse. A detailed mechanistic investigation based on spectroscopic and crystallographic analysis revealed that a putative reductive elimination to forge C(sp3)-OC(sp3) using I2 might not be operative. We isolated a paramagnetic bimetallic NiIII intermediate featuring a unique Ni2(OR)2 (OR = alkoxide) diamond-like core complemented by a μ-iodo bridge between the two Ni centers, which remains stable at low temperatures, thus permitting its characterization by NMR, EPR, X-ray, and HRMS. At higher temperatures (>-10 °C), such bimetallic intermediate thermally decomposes to afford large amounts of elimination products together with iodoalkanols. Observation of the latter suggests that a C(sp3)-I bond reductive elimination occurs preferentially to any other challenging C-O bond reductive elimination. Formation of cyclized THF rings is then believed to occur through cyclization of an alcohol/alkoxide to the recently forged C(sp3)-I bond. The results of this article indicate that the use of F+ oxidants permits the challenging C(sp3)-OC(sp3) bond formation at a high-valent nickel center to proceed in good yields while minimizing deleterious elimination reactions. Preliminary investigations suggest the involvement of a high-valent bimetallic NiIII intermediate which rapidly extrudes the C-O bond product at remarkably low temperatures. The new set of conditions permitted the elusive synthesis of diethyl ether through reductive elimination, a remarkable feature currently beyond the scope of Ni.
Carbohydrate/DBU Cocatalyzed Alkene Diboration: Mechanistic Insight Provides Enhanced Catalytic Efficiency and Substrate Scope
Yan, Lu,Meng, Yan,Haeffner, Fredrik,Leon, Robert M.,Crockett, Michael P.,Morken, James P.
supporting information, p. 3663 - 3673 (2018/03/21)
A mechanistic investigation of the carbohydrate/DBU cocatalyzed enantioselective diboration of alkenes is presented. These studies provide an understanding of the origin of stereoselectivity and also reveal a strategy for enhancing reactivity and broadening the substrate scope.
