A Catalytic Asymmetric Ring‐Expansion Reaction of Isatins and α‐Alkyl‐α‐Diazoesters: Highly Efficient Synthesis of Functionalized 2‐Quinolone Derivatives

Abstract

Asymmetric expansion: A catalytic asymmetric ring-expansion reaction of the title compounds occurs in the presence of a Sc(OTf)(3) catalyst bearing an N,N'-dioxide-based ligand. Highly functionalized 2-quinolone derivatives containing a chiral C4-quaternary stereocenter were obtained in high yields and high levels of selectivity under mild reaction conditions (see scheme; Tf=trifluoromethanesulfonyl).

Catalytic Asymmetric Intramolecular Homologation of Ketones with α‐Diazoesters: Synthesis of Cyclic α‐Aryl/Alkyl β‐Ketoesters

“…Examples of catalytic asymmetric Roskamp reaction (also known as Roskamp–Feng reaction) with aromatic and aliphatic aldehydes have recently been reported 6. Enantioselective ring expansions of cyclohexanones7 and isatins8a with diazo compounds could give access to seven‐membered rings and 2‐quinolone derivatives, respectively. Activated α‐ketoesters underwent asymmetric intermolecular homologation to afford succinate derivatives with chiral quaternary centers 8b.…”

Highly Selective Catalyst-Dependent Competitive 1,2-C→C, -O→C, and -N→C Migrations from β-Methylene-β-silyloxy-β-amido-α-diazoacetates

“…2 Among the reactions that encompass these 1,2-migrations are the semipinacol rearrangement and its multiple varients, 3 solvolysis reactions 1d that include Wagner-Meerwein rearrangements, 4 ring-enlargement reactions 5 and, more recently, gold-catalyzed migrations. 6 With free rotation around the C–C bond to the electrophilic carbon, group migration is dependent upon migratory aptitude as well as on the spacial positioning of the migrating group relative to the electrophilic center.…”

“…1a,b, 4a, 4c In general, although highly selective migrations are most desirable, competition between two migrating groups is commonly observed. 1c, 5b,c In these reactions the product that is formed is dependent on the structure of the reactant, 4a,b,e and external control of which group migrates has long been problematic. 3,4 Catalytically generated metal carbenes from α-diazo carbonyl compounds are highly electrophilic, and 1,2-migration occurs if a saturated carbon is directly bonded to the carbene center.…”

Catalytic Asymmetric Halogenation/Semipinacol Rearrangement of 3‐Hydroxyl‐3‐vinyl Oxindoles: A Stereodivergent Kinetic Resolution Process

“…Racemic 3‐hydroxyl‐3‐vinyl oxindoles, which contain a popular and valuable skeleton, [9] were synthesized for the rearrangement (Scheme 1 c). It was found that in the assistance of scandium complex of chiral N , N ′‐dioxide, both optically active dihydroquinoline‐2,4‐diones and dihydroquinoline‐2,3‐diones containing quaternary stereocenters could be obtained simultaneously with high efficiency and excellent enantioselectivities [10] …”