Lewis Acid Activation of Fragment-Coupling Reactions of Tertiary Carbon Radicals Promoted by Visible-Light Irradiation of EDA Complexes
作者:Spencer P. Pitre、Tyler K. Allred、Larry E. Overman
DOI:10.1021/acs.orglett.1c00023
日期:2021.2.5
The addition of tertiary carbon radicals generated from N-(acyloxy)phthalimide esters to cyclic α,β-unsaturated ketones and lactones is markedly enhanced by the addition of substoichiometric amounts of a Ln(OTf)3. The reaction is accomplished by irradiation with visible light in the absence of a photosensitizer and is suggested to proceed by excitation of a ternary electron donor–acceptor complex between
Efforts toward the total synthesis of (±)-toxicodenane A utilizing an oxidopyrylium-based [5+2] cycloaddition of a silicon-tethered BOC-pyranone
作者:Jacob P. Grabowski、Gregory M. Ferrence、T. Andrew Mitchell
DOI:10.1016/j.tetlet.2020.152324
日期:2020.9
Synthetic efforts toward the tricyclic core of (±)-toxicodenane A are reported. This strategy takes advantage of the Feist-Benary furan annulation, Achmatowicz oxidative rearrangement, and oxidopyrylium-based [5+2] cycloaddition to access a key tetracyclic intermediate. This work provides a foundation that can be utilized toward the totalsynthesis of the natural product.
Silica gel enables Achmatowicz rearrangement with KBr/oxone under “anhydrous” condition for one-pot functionalization
作者:Guodong Zhao、Rongbiao Tong
DOI:10.1016/j.tet.2018.12.022
日期:2019.3
Silica gel was found to effectively promote Achmatowiczrearrangement (AchR) using KBr/oxone under near anhydrous condition. This new protocol allows direct functionalization of AchR products in a one-pot manner, effectively reducing the cost, time, and environmental impacts derived from the conventional stop-and-go approach using separate reaction vessels. These advantages were demonstrated in four
Intramolecular cycloadditions with oxidopyrylium ylides
作者:Peter G. Sammes、Leslie J. Street
DOI:10.1039/c39820001056
日期:——
3-Oxopyrans, bearing unsaturated side Chains, can undergo intramolecular reactions, either by thermal or base-catalysed processes, to yield bicyclic adducts and affording, for example, a simple entry into the perhydroazulene system.
Dual Catalysis in Enantioselective Oxidopyrylium-Based [5 + 2] Cycloadditions
作者:Noah Z. Burns、Michael R. Witten、Eric N. Jacobsen
DOI:10.1021/ja206997e
日期:2011.9.21
A new method for effecting catalytic enantioselective intramolecular [5 + 2] cycloadditions based on oxidopyrylium intermediates is reported. The dual catalyst system consists of a chiral primary aminothiourea and a second achiral thiourea. Experimental evidence points to a new type of cooperative catalysis with each species being necessary to generate a reactive pyrylium ion pair that undergoes subsequent cycloaddition with high enantioselectivity.