Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

Abstract

SummaryCopper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives were investigated. The regioselectivities of these processes were found to be influenced by the structure of cyclopropanols as well as the counter anion of the copper(II) salts. A mechanism involving rearrangement reactions of radical intermediates and their competitive trapping by copper ions is proposed.

Cu(OTf)2-Catalyzed Intramolecular Radical Cascade Reactions for the Diversity-Oriented Synthesis of Quinoline-Annulated Polyheterocyclic Frameworks

“…Based on our observations and previous reports, − the proposed mechanism for the synthesis of quinoline-annulated polyheterocyclic scaffolds is shown in Scheme . Initially, the intermediate M0 is generated in situ from methyl 2-((2-aminophenyl)­ethynyl)­benzoate ( 1a ) and benzaldehyde ( 2n ) through TsOH-promoted condensation.…”

Selective Carbon–Carbon Bond Cleavage of Cyclopropanols

“…204 Zhang and co-workers have reported the addition of cyclopropyl alcohols into iminium ions formed from aerobic C−H oxidation as an efficient way to form azabicyclo[3.3.1]nonane scaffolds (397, Scheme 90). 205,206 This coppercatalyzed protocol was used in the total synthesis of (−)-suaveoline. The iminium 394, generated via oxidation of the corresponding amine by CuCl 2 , is attacked by the β-keto radical (395), resulting in the formation of 396.…”

Enantioselective Copper‐Catalyzed Radical Ring‐Opening Cyanation of Cyclopropanols and Cyclopropanone Acetals

“…The reaction is initiated by a (L*)Cu I CN species, which can be oxidized by BPO to give the copper(II) species A. Cyclopropanol 1 then coordinates to the copper center of A, before intramolecular deprotonation occurs with int-V to yield a key intermediate int-I. [19] After homolytic cleavage of OÀ Cu II bond of int-I, [20] the generated cyclopopoxy radical int-III undergoes rapid ring-opening to generate a distal benzylic radical int-IV. Meanwhile, the active radical species BzO * , generated from initial SET process, [21] is trapped by (L*)Cu I (CN) to form another copper(II) complex A, [22] which reacts with TMSCN to give (L*)Cu II (CN) 2 (B).…”