Core‐Structure‐Oriented Asymmetric Organocatalytic Substitution of 3‐Hydroxyoxindoles: Application in the Enantioselective Total Synthesis of (+)‐Folicanthine

Catalytic Stereoselective Synthesis of Diverse Oxindoles and Spirooxindoles from Isatins

“…22 The enantiomerically-enriched N -propargylated 3-hydroxy-oxindoles were subjected to the CuAAC conditions with azides 12a – c, e (Table 4, entries 1–14). The enantiomeric excess of the triazole-containing 3-hydroxy3-indolyl-oxindole 4ba was confirmed by HPLC analysis using chiral stationary phase by comparison to the triazoles produced by racemic synthesis.…”

Recent Developments in the Catalytic, Asymmetric Construction of Pyrroloindolines Bearing All-Carbon Quaternary Stereocenters

“…18 In a 2009 report, Stoltz and coworkers describe a Cu(II) bisoxazoline ( 23 )-catalyzed stereoablative alkylation of 3-chloro-3-aryloxindoles ( 22 ) with dimethylmalonate, wherein coordination of the malonate to the copper catalyst presumably generates a chiral nucleophile ( 24 , Scheme 4). 18a The reaction is proposed to occur by elimination of HCl from 22 to form a transient o -azaxylylene ( 25 ); subsequent attack at C3 by 24 delivers the 3,3′-disubstituted oxindole ( 26 ). The utility of these products in pyrroloindoline synthesis was demonstrated for oxindole 26 , which following Krapcho dealkoxycarbonylation, N -methylation, aminolysis, and reductive cyclization afforded 3-phenylpyrroloindoline 28 in an operationally straightforward manner.…”

“…18b This reaction involves indole-assisted dehydration, followed by chiral phosphoric acid ( 31 )-catalyzed addition of enamine 30 to the transient azafulvene (Scheme 5). Mechanistic insight was provided by DFT calculations, which suggest a two-point binding model for the Brønsted acid that invokes hydrogen bonding of both the enamine and indole nitrogens (see proposed transition structure 32 ).…”

Organocatalytic asymmetric synthesis of chiral nitrogenous heterocycles and natural products

“…The intermediate 25 was planned to be accessed by classical transformations from 26, which is principally able to be prepared from 27 by Beckmann rearrangement or sequential Baeyer-Villiger oxidation/amidation reaction. Obviously, the development of asymmetric catalytic reaction to generate compound 27 is the key point of the total synthesis [17].…”