Cu(ii)-catalyzed enantioselective oxygen atom transfer from oxaziridine to oxindole derivatives with chiral phenanthroline

Abstract

In the presence of a Cu(ii) complex of axially chiral, N,N,O-tridentate phenanthroline ligand (S)-2, asymmetric oxygen atom transfer of oxindole derivatives (3) using Davis' oxaziridine (4) occurred to give the corresponding 3-aryl-3-hydroxy-2-oxindole derivatives (1) with excellent enantioselectivity (up to 96% ee). The X-ray crystallographic analysis of the isolated Cu(ii) complex disclosed its N,N,O-tridentate coordination, which is critical to realize effective catalytic activity.

Recent advances in the asymmetric catalytic synthesis of chiral 3-hydroxy and 3-aminooxindoles and derivatives: Medicinally relevant compounds

“…The enantioselective oxygen atom transfer from an oxaziridine to different 3-aryl-oxindole derivatives was reported by Naganawa et al [154]. The best results were achieved using Cu(OAc) 2 and ligand L8 (Scheme 38) as the chiral catalyst, with good yields and very good enantioselectivities for the 3-aryl-3-hydroxy-oxindole derivatives obtained [154].…”

Cu(II)‐catalyzed Enantioselective α‐Hydroxylation and α‐Chlorination of β‐Ketoesters with N,N,O‐Tridentate Chiral Phenanthroline Ligand

“…Next, a possible mechanism for asymmetric induction based on the absolute configuration of 6 is proposed (Figure ). Formation of the intermediate is analogous to Davis’ oxidation of N ‐Boc oxindole derivatives 2 . The generation of the Cu(II) enolate of 5 a occurs to give two different intermediates, I‐1 and I‐2 , because the chiral ligand ( S )‐ 1 a possesses C 1 symmetry.…”

Renovation of Optically Active Phenanthrolines as Powerful Chiral Ligands for Versatile Asymmetric Metal Catalysis

“…The design of ( S )‐ 1 is based on the concept of renovation of optically active phen derivatives as chiral ligands efficient for versatile asymmetric metal catalysis. Our endeavor to develop enantioselective transformations has been devoted to several enantioselective reactions such as (i) addition of organozinc reagents to aldehydes,11 (ii) Zn(II)‐catalyzed electrophilic amination of β‐ketoesters with azodicarboxylate,21 (iii) Cu(II)‐catalyzed α‐hydroxylation of oxindole derivatives,26 (iv) Ni(II)‐catalyzed Michael addition of oxindole derivatives to MVK,27 and (v) Rh(I)‐catalyzed intramolecular hydrosilylation for the construction of chiral silicon stereogenic centers 30. Further applications using other metal catalysts are ongoing to broaden the utility of ( S )‐ 1 .…”

“…Several research groups have designed their own chiral ligands for metal‐catalyzed enantioselective α‐hydroxylation of carbonyl compounds using Davis's oxaziridine (Davis oxidation) 25. In this context, we applied chiral phen ligands ( S )‐ 1 to Cu(II)‐catalyzed enantioselective Davis oxidation 26…”