Dearomative [4+2] Cycloaddition of Oxindole‐Embeddedortho‐Quinone Methides with 2,5‐Dialkylfurans

Palladium-Catalyzed [4+4] Cycloadditions for Highly Diastereo- and Enantioselective Synthesis of Functionalized Benzo[b]oxocines

Asymmetric cycloaddition reactions represent a powerful strategy for building up complex molecular architectures, especially those with medium-sized rings. Herein, we disclose a highly diastereo- and enantioselective cycloaddition strategy that involves...

Stereoselective synthesis and applications of spirocyclic oxindoles

This review summaries recent synthetic developments towards spirocyclic oxindoles and applications as valuable medicinal and synthetic targets.

Regio- and stereoselective synthesis of spiropyrrolidine-oxindole and bis-spiropyrrolizidine-oxindole grafted macrocycles through [3 + 2] cycloaddition of azomethine ylides

A convenient and efficient method for the regioselective macrocyclization of triazole bridged spiropyrrolidine-oxindole, and bis-spiropyrrolizidine-oxindole derivatives was accomplished through intra and self-intermolecular [3 + 2] cycloaddition of azomethine ylides. The chalcone isatin precursors 9a-i required for the click reaction were obtained from the reaction of N-alkylazidoisatin 4 and propargyloxy chalcone 8a-i which in turn were obtained by the aldol condensation of propargyloxy salicylaldehyde 6 and substituted methyl ketones 7a-i. The regio- and stereochemical outcome of the cycloadducts were assigned based on 2D NMR and confirmed by single crystal XRD analysis. High efficiency, mild reaction conditions, high regio- and stereoselectivity, atom economy and operational simplicity are the exemplary advantages of the employed macrocyclization procedure.

Organocatalytic C3-functionalization of indolizines: synthesis of biologically important indolizine derivatives

A Brønsted acid-catalyzed C3-alkylation of indolizines has been established with different electrophiles such as ortho-hydroxybenzyl alcohols, other precursors of para-quinone methides and ortho-quinone methides, and 2-indolylmethanol as well. By using this approach, a series of C3-functionalized indolizines were synthesized in overall good yields (up to 89%). These examples demonstrate that the Brønsted acid-catalyzed C3-alkylation of indolizines has a wide applicability, which can serve as a useful method for synthesizing C3-functionalized indolizine derivatives with structural diversity. This reaction has fulfilled the task of developing organocatalytic C3-functionalization of indolizines for the synthesis of biologically important indolizine derivatives.

Divergent syntheses of spirooxindoles from oxindole-embedded four-membered synthon via cycloaddition reactions

The construction of five and six membered heterocycle fused spirooxindoles was achieved via the [4 + 1] and formal [4 + 2] cycloadditions between our rationally designed four-membered synthons and pyridinium methylides and α-bromoacetophenones, respectively.

Organocatalytic [4 + 2] cyclizations of para-quinone methide derivatives with isocyanates

The first [4 + 2] cyclizations of o-hydroxyphenyl-substituted p-quinone methide derivatives with isocyanates have been established under the catalysis of Brønsted acids or Brønsted bases, which efficiently constructed benzoxazin-2-one frameworks in generally high yields.