Catalytic Desymmetrization of meso-Aziridines with Benzofuran-2(3H)-Ones Employing a Simple In Situ-Generated Magnesium Catalyst

Asymmetric magnesium catalysis for important chiral scaffold synthesis

Magnesium catalysts are widely used in catalytic asymmetric reactions, and a series of catalytic strategies have been developed in recent years. Herein, in this review, we have tried to summarize asymmetric magnesium catalysis for the synthesis of important chiral scaffolds. Several important optically active motifs that are present in classic chiral ligands or natural products synthesized by Mg(II) catalytic methods are briefly discussed. Moreover, the representative mechanisms for different magnesium catalytic strategies, including in situ generated magnesium catalysts, are also shown in relation to synthetic routes for obtaining these important chiral scaffolds.

Catalytic enantioselective desymmetrization of meso-aziridines

As a type of readily available small strained-ring heterocycle, meso-aziridines may undergo catalytic desymmetrizing transformations to empower the rapid construction of diverse nitrogen-containing structures bearing contiguous stereocenters, which have great relevance in natural product synthesis, drug development and the design and synthesis of chiral catalysts/ligands for asymmetric catalysis. This review outlines the advances achieved in the catalytic asymmetric desymmetrization of meso aziridines and highlights some promising avenues for further work in this realm.

Synthesis of chiral pyridine-oxazolines via catalytic asymmetric Heine reaction of meso-N-(2-picolinoyl)-aziridines

An asymmetric Heine reaction of (meso)-N-(2-picolinoyl)-aziridines catalyzed by a chiral ytterbium(III)–N,N’-dioxide complex was established. A novel library of pyridine-oxazolines was obtained in decent yields and enantioselectivities, which show potential as...

Synthesis of chiral β-substituted γ-amino-butyric acid derivatives via enantioconvergent ring opening of racemic 2-(hetero)aryl aziridines with ketene silyl acetals

Lewis acid-catalyzed enantioconvergent ring opening of racemic 2-(hetero)aryl-N-sulfonyl aziridines with ketene silyl acetals is developed.

Palladium-Catalyzed, Enantioselective Desymmetrization of N-Acylaziridines with Indoles

Ring opening reactions of meso-aziridines generate chiral amine derivatives where the control of stereochemistry is possible through enantioselective catalysis. We report the use of a diphosphine-palladium(II) catalyst for the highly enantioselective desymmetrization of N-acylaziridines with indoles. The β-tryptamine products are isolated in moderate to high yield across a range of indole and aziridine substitution patterns. The synthetic utility of β-tryptamine products is demonstrated by conversion to the brominated pyrroloindoline derivative.

Aziridine used as a vinylidene unit in palladium-catalyzed [2 + 2 + 1] domino annulation

A series of chromone fused methylenecyclopentanes are efficiently constructed in moderate to good yields by Pd-catalyzed [2 + 2 + 1] annulation, in which aziridine is used as a vinylidene unit by cleavage of two C–N bonds for the first time.

Mg(OMe)2 promoted allylic isomerization of γ-hydroxy-α,β-alkenoic esters to synthesize γ-ketone esters

This work concerns the Mg(OMe)₂ promoted allylic isomerization of γ-hydroxy-α,β-alkenoic esters with TMEDA as an additive. The isomerization proceeded under mild conditions and afforded γ-keto esters in high yield (up to 96%) within 2 h. Both (Z)- and (E)-γ-hydroxy-α,β-alkenoic esters were tolerated under the reaction conditions. This transformation involves the in situ formation of a dienolate intermediate from the easily accessible γ-hydroxy-α,β-alkenoic ester. The in situ generated dienolate can react with benzaldehyde and undergo a practical, useful tandem allylic isomerization-Aldol reaction to afford more functionalized compounds.

An enantioselective conjugate addition reaction of 3-substituted benzothiophen-2-ones and 2-phthalimidoacrylates

A highly enantioselective conjugate addition reaction of 3-substituted benzothiophen-2-ones to 2-phthalimidoacrylates has been developed using a bifunctional tertiary-amine thiourea catalyst.

Enantioselective magnesium-catalyzed transformations

This review updates the major progress in the field of enantioselective transformations promoted by chiral magnesium catalysts, covering the literature since 2007, illustrating the power of these green catalysts to promote many types of reactions.

Desymmetrization of aziridine with malononitrile using cinchona alkaloid amide/zinc(ii) catalysts

The catalytic enantioselective desymmetrization of aziridines with malononitrile has been developed.

Palladium-Catalyzed, Enantioselective Heine Reaction

Aziridines are important synthetic intermediates for the generation of nitrogen-containing molecules. N-Acylaziridines undergo rearrangement by ring expansion to produce oxazolines, a process known as the Heine reaction. The first catalytic, enantioselective Heine reaction is reported for meso-N-acylaziridines where a palladium(II)-diphosphine complex is employed. The highly enantioenriched oxazoline products are valuable organic synthons and potential ligands for transition-metal catalysis.

Diastereoselective synthesis of cyclopentene spiro-rhodanines containing three contiguous stereocenters via phosphine-catalyzed [3 + 2] cycloaddition or one-pot sequential [3 + 2]/[3 + 2] cycloaddition

5-Spiro-cyclopentene-rhodanine derivatives have been synthesized through two different diastereoselective phosphine-catalyzed cascade reactions in excellent diastereoselectivities and good to excellent yields.

Simple magnesium catalyst mediated γ-butyrolactams in desymmetrization of meso-aziridines

The first α-sp²-carbon of carbonyl compounds attacked catalytic desymmetrization reaction of aziridines is disclosed by employing a simple in situ generated magnesium catalyst.