Diastereoselective [3 + 1] Cyclization Reaction of Oxindolyl Azaoxyallyl Cations with Sulfur Ylides: Assembly of 3,3'-Spiro[β-lactam]-oxindoles

AlCl3-Promoted Intramolecular Indolinone-Quinolone Rearrangement of Spiro[indoline-3,2'-quinoxaline]-2,3'-diones: Easy Access to Quinolino[3,4-b]quinoxalin-6-ones

A facile and direct intramolecular indolinone-quinolone rearrangement was developed for the synthesis of quinolino[3,4-b]quinoxalin-6-ones from spiro[indoline-3,2'-quinoxaline]-2,3'-diones, which are readily available with use of isatines, malononitrile, and 1,2-phenylenediamines under quite mild conditions. This efficient approach provides excellent yields and could potentially be used for the construction of a diverse library of quinolino[3,4-b]quinoxalin-6-ones for high-throughput screening in medicinal chemistry. The reaction mechanism is explored by extensive DFT calculations.

A concise approach to 2-pyrrolin-5-one scaffold construction from α-halohydroxamates and β-keto compounds

A concise approach to the construction of the 2-pyrrolin-5-one scaffold was developed via a one-pot reaction with formal [3 + 2] annulation/elimination between β-keto nitrile/β-keto ester and unsubstituted α-halohydroxamates. This reaction features mild conditions, easy handling, broad substrate scope and good yields. Remarkably, the products could be readily converted into potentially bioactive alkylidenepyrrolinones, pyrroles, pyran-fused pyrrole heterocycles and other useful compounds, exhibiting versatile synthetic potential.

Expedient (3+3)-annulation of in situ generated azaoxyallyl cations with diaziridines

Efficient annulation of in situ formed azaoxyallyl cations using a base has been accomplished with diaziridines to provide 1,2,4-triazines at room temperature. The substrate scope, scale up, functional group tolerance and transition-metal free reaction conditions are the important practical features.

Heteroarylation of Congested α-Bromoamides with Imidazo-Heteroarenes and Indolizines via Aza-Oxyallyl Cations: Enroute to Dibenzoazepinone and Zolpidem Analogues

Herein, we report a highly efficient and unprecedented approach for heteroarylation of congested α-bromoamides via electrophilic aromatic substitution of imidazo-heteroarenes and indolizines under mild reaction conditions (room temperature, metal, and oxidant free). The participation of an in situ generated aza-oxyallyl cation as an alkylating agent is the hallmark of this transformation. The method was readily adapted to synthesize novel imidazo-heteroarene-fused dibenzoazepinone architectures of potential medicinal value.

Access to 3,3'-disubstituted peroxyoxindole derivatives and α-peroxyamides via azaoxyallyl cation-guided addition of hydroperoxides

Herein, a transition metal-free approach for access to 3,3'-disubstituted peroxyoxindole is disclosed, which harnesses a transient azaoxyallyl cation. This strategy is also applicable to the synthesis of structurally diverse α-peroxycarboxylic acid surrogates. The method exhibits good functional group tolerance and is suitable for generating a library of peroxy-containing compounds.

Synthesis of spirocyclic oxazole derivatives from 2-arylidene cycloalkanones and α-halohydroxamates

Herein we disclose a facile route to spirocyclic oxazole derivatives via [3 + 2] cycloaddition reactions between 2-arylidene cycloalkanones and azaoxyallyl cations that formed in situ from α-halohydroxamates in the presence of base. This methodology was shown to lead to an efficient formation of a series of functionalized spirocyclic oxazole derivatives in good to excellent yields.

Sulphur ylide-mediated cyclopropanation and subsequent spirocyclopropane rearrangement reactions

The efficient construction of cyclopropyl spiroindoline skeletons and the exploration of related follow-up synthetic transformations have elicited considerable interest amongst members of the chemistry community. Here, we describe a formal (2 + 1) annulation and three-component (1 + 1 + 1) cascade cyclisation via sulphur ylide cyclopropanation under mild conditions. The spiro-cyclopropyl iminoindoline moiety can be readily transformed into another medicinally interesting pyrrolo[3,4-c]quinoline framework through a novel rearrangement process.

Base-Promoted Formal [3 + 2] Cycloaddition of α-Halohydroxamates with Carbon Disulfide to Synthesize Polysubstituted Rhodanines

A concise and practical strategy via potassium-carbonate-mediated [3 + 2]-cycloaddition reaction of α-halohydroxamates with the common solvent carbon disulfide for the synthesis of functionalized rhodanine derivatives in good to excellent yields is developed. The present methodology features a wide substrate scope as well as good functional group tolerance. The potential synthetic utility of this protocol is demonstrated by synthesis of a series of natural product derivatives containing rhodamine skeletons.

Enantioselective Synthesis of Azetidines through [3 + 1]-Cycloaddition of Donor-Acceptor Aziridines with Isocyanides

The enantioselective [3 + 1]-cycloaddition of racemic donor-acceptor (D-A) aziridines with isocyanides was first realized under mild reaction conditions using a chiral N,N'-dioxide/Mg^II complex as catalyst, providing a facile route to enantioenriched exo-imido azetidines with good to excellent yield (up to 99%) and enantioselectivity (up to 94% ee). An obvious chiral amplification effect was observed in this system, and an explanation was elucidated based on the experimental investigation and X-ray crystal structure of the enantiomerically pure catalyst.

Base-mediated unprecedented tandem cyclization reaction of nitrilimines and sulfur ylides: facile approaches to multifunctionalized pyrazolines

An interesting three-component tandem reaction between hydrazonoyl chlorides and α-keto-derived sulfonium salts is reported. Highly substituted pyrazolines were obtained in moderate to excellent yield under mild conditions. Moreover, α-keto-stabilised sulfur...

Diastereoselective formation of β-lactams via a three-component reaction

A highly diastereoselective three-component reaction of N-hydroxyanilines, diazo compounds and cyclobutenones to form densely functionalized β-lactams has been realized.

Synthesis of functionalized 3,2′-pyrrolidinyl spirooxindoles via domino 1,6-addition/annulation reactions of para-quinone methides and 3-chlorooxindoles

A highly efficient diastereoselective [4 + 1] cycloaddition of ortho-tosylaminophenyl-substituted p-QMs with 3-chlorooxindoles has been developed to afford 3,2′-pyrrolidinyl spirooxindoles.