Access to Diverse Seleno-spirocyclohexadienones via Ag(II)-Catalyzed Selenylative ipso-Annulation with Se and Boronic Acids

Abstract

An efficient and straightforward synthesis of diversified seleno-azaspiro-2,5-cyclohexadienones from N-(4-methoxy aryl)­propiolamides using elemental selenium and boronic acids has been demonstrated. The reaction proceeds through silver-catalyzed oxidative dearomatization in the presence of potassium persulfate (K2S2O8) as the oxidant. Further, this approach was extended to N-(4-methoxy aryl)­propiolates and biaryl ynones to access the corresponding selenylated oxospiro-2,5-cyclohexadienones and spiro­[5,5]­trienones, respectively. The present three-component method offers the diverse substitutions on selenium involving two C–Se and one C–C bond formations.

Silver-catalyzed synthesis of nitrogen heterocycles: recent advancements

“…This silver-alkyne complex In 2022, Reddy and co-workers synthesized a variety of seleo-spirocyclohexadienones 76 via selenylative ipso-annulation using Ag(II)-catalysis. 70 This straightforward synthesis was achieved by reacting N-(4-methoxy aryl)propiolamides 72 with boronic acids 73 and elemental selenium 74 in the presence of 10 mol% AgNO 3 63, 2.5 equiv. K 2 S 2 O 8 (oxidant) in 1,4-dioxane at 120 °C for 10-16 h, and afforded the desired seleno-spiricycles 76 in high to excellent yields (Scheme 23).…”

Recent Approaches in Transition Metal-Catalyzed Chalcogenative Heteroannulation of Alkenes and Alkynes

“…Then, this radical is oxidized to cati species, which reacts with the o-methyloxime, forming cationic species XXX hydrolysis, yields the desired Se-containing cyclic product 37 and methano uct. In 2022, Reddy and coworkers reported an elegant protocol to perform neous C-Se and C-C bond formation through Ag-catalyzed oxidative de multicomponent process by reacting carbonylated-alkynes with boronic a nium powder [65]. The best reaction condition still employs AgNO2 (10 mol K2S2O8 (2.5 equiv.)…”

Ag(i)-catalyzed three-component radical cascade synthesis of 3-organoselenyl chromones from 2-methoxyaryl alkynones, Se powder and organic boronic acids

“…In this strategy, Se powder was firstly activated by aryl radicals derived from aryl boronic acids to form organoselenium-centered radicals, followed by the addition to ortho -methoxy or methylthio substituted aryl alkynyls to trigger a cascade intramolecular cyclization reaction. Later on, the Liu group and Reddy successively extended this concept to the organoselenation of other heterocycles, such as isochromenones, 20 isoxazoles, 21 azaspiro-2,5-cyclohexadien-ones 22 and others, 23 by employing various functionalized alkyne and aryl group-containing compounds as radical acceptors. Inspired by these works as well as our continuous interest in organoselenium chemistry, 24 we herein report a new three-component radical cascade cyclization approach for 3-organoselenyl chromone synthesis from 2-methoxyaryl alkynones, aryl boronic acids and Se powder (Scheme 1D).…”