Ru-Catalyzed Redox-Neutral Cleavage of the N–O Bond in Isoxazolidines: Isatogens to Pseudoindoxyls via a One-Pot [3 + 2]-Cycloaddition/N–O Cleavage

Abstract

A novel metal-catalyzed oxygen atom transfer reaction onto olefins is reported. By taking isatogens as substrates, a one-pot [3 + 2]-cycloaddition of nitrone with olefins followed by the Ru-catalyzed redox-neutral N-O bond cleavage of intermediate isoxazolidine has been executed as a simple method for the synthesis of 2,2-disubstituted pseudoindoxyls.

Isoxazolidine: A Privileged Scaffold for Organic and Medicinal Chemistry

“…For the preparation of β-aminoketones 192, Kumar and Ramana 217 4.2.2. Synthesis of N-Oxide-1,3-amino Alcohols.…”

Direct Oxidative Dearomatization of Indoles with Aromatic Ketones: Rapid Access to 2,2-Disubstituted Indolin-3-ones

“…4 As a subset, the synthesis of 2,2-disubstituted indolin-3-ones bearing 2oxo-2-phenylethyl at C2 position have attracted great interest since multiple functional groups leave potential functionalities for further chemical transformations. [5][6][7][8][9][10] In 2009, Kawasaki and co-workers reported a Mannich-type reaction of 2-hydroxy-1,2-dihydro-3H-indol-3-ones with various carbon nucleophiles to give the products in good yields (Scheme 1a). 5 In 2015, Ramana and co-workers reported a Ru-catalyzed redox-neutral cleavage of the N-O bond for the synthesis of 2,2-disubstituted indolin-3-ones (Scheme 1a).…”

“…5 In 2015, Ramana and co-workers reported a Ru-catalyzed redox-neutral cleavage of the N-O bond for the synthesis of 2,2-disubstituted indolin-3-ones (Scheme 1a). 6 Recently, Miao's group described a Cs 2 CO 3catalyzed reaction of 2-oxindoles with enones for the preparation of indolin-3-ones and demonstrated the synthetic potential of the desired products (Scheme 1a). 7 Impressive progress has also been made in asymmetric construction of 2,2-disubstituted indolin-3-ones; 8 Ma's group disclosed chiral phosphoric acid catalyzed direct asymmetric Mannich reaction of cyclic C-acylimines with ketones and difluoroenoxysilanes (Scheme 1a).…”

A General Approach to the Aza-Diketomorpholine Scaffold

“…Nitrogen- or oxygen-containing heterocycles involving a wide range of natural and bioactive molecules have attracted considerable attention due to their interesting potential in organic and medicinal chemistry. − Accordingly, recent curiosity was devoted to heterocycles bearing both nitrogen and oxygen as adjacent atoms. − Although such a cyclic platform was generally less studied, its importance for organic chemists and drug designers is well established. − Indeed, conformational restriction by cyclization is also a popular tactic for optimizing the hit-to-lead process (Figure ).…”